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+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "/usr/share/xml/docbook/schema/dtd/4.5/docbookx.dtd">
+
+<book>
+ <title>AltOS</title>
+ <subtitle>Altos Metrum Operating System</subtitle>
+ <bookinfo>
+ <author>
+ <firstname>Keith</firstname>
+ <surname>Packard</surname>
+ </author>
+ <copyright>
+ <year>2010</year>
+ <holder>Keith Packard</holder>
+ </copyright>
+ <legalnotice>
+ <para>
+ This document is released under the terms of the
+ <ulink url="http://creativecommons.org/licenses/by-sa/3.0/">
+ Creative Commons ShareAlike 3.0
+ </ulink>
+ license.
+ </para>
+ </legalnotice>
+ <revhistory>
+ <revision>
+ <revnumber>0.1</revnumber>
+ <date>22 November 2010</date>
+ <revremark>Initial content</revremark>
+ </revision>
+ </revhistory>
+ </bookinfo>
+ <chapter>
+ <title>Overview</title>
+ <para>
+ AltOS is a operating system built for the 8051-compatible
+ processor found in the TI cc1111 microcontroller. It's designed
+ to be small and easy to program with. The main features are:
+ <itemizedlist>
+ <listitem>
+ <para>Multi-tasking. While the 8051 doesn't provide separate
+ address spaces, it's often easier to write code that operates
+ in separate threads instead of tying everything into one giant
+ event loop.
+ </para>
+ </listitem>
+ <listitem>
+ <para>Non-preemptive. This increases latency for thread
+ switching but reduces the number of places where context
+ switching can occur. It also simplifies the operating system
+ design somewhat. Nothing in the target system (rocket flight
+ control) has tight timing requirements, and so this seems like
+ a reasonable compromise.
+ </para>
+ </listitem>
+ <listitem>
+ <para>Sleep/wakeup scheduling. Taken directly from ancient
+ Unix designs, these two provide the fundemental scheduling
+ primitive within AltOS.
+ </para>
+ </listitem>
+ <listitem>
+ <para>Mutexes. As a locking primitive, mutexes are easier to
+ use than semaphores, at least in my experience.
+ </para>
+ </listitem>
+ <listitem>
+ <para>Timers. Tasks can set an alarm which will abort any
+ pending sleep, allowing operations to time-out instead of
+ blocking forever.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <para>
+ The device drivers and other subsystems in AltOS are
+ conventionally enabled by invoking their _init() function from
+ the 'main' function before that calls
+ ao_start_scheduler(). These functions initialize the pin
+ assignments, add various commands to the command processor and
+ may add tasks to the scheduler to handle the device. A typical
+ main program, thus, looks like:
+ <programlisting>
+void
+main(void)
+{
+ ao_clock_init();
+
+ /* Turn on the LED until the system is stable */
+ ao_led_init(LEDS_AVAILABLE);
+ ao_led_on(AO_LED_RED);
+ ao_timer_init();
+ ao_cmd_init();
+ ao_usb_init();
+ ao_monitor_init(AO_LED_GREEN, TRUE);
+ ao_rssi_init(AO_LED_RED);
+ ao_radio_init();
+ ao_packet_slave_init();
+ ao_packet_master_init();
+#if HAS_DBG
+ ao_dbg_init();
+#endif
+ ao_config_init();
+ ao_start_scheduler();
+}
+ </programlisting>
+ As you can see, a long sequence of subsystems are initialized
+ and then the scheduler is started.
+ </para>
+ </chapter>
+ <chapter>
+ <title>Programming the 8051 with SDCC</title>
+ <para>
+ The 8051 is a primitive 8-bit processor, designed in the mists
+ of time in as few transistors as possible. The architecture is
+ highly irregular and includes several separate memory
+ spaces. Furthermore, accessing stack variables is slow, and the
+ stack itself is of limited size. While SDCC papers over the
+ instruction set, it is not completely able to hide the memory
+ architecture from the application designer.
+ </para>
+ <section>
+ <title>8051 memory spaces</title>
+ <para>
+ The __data/__xdata/__code memory spaces below were completely
+ separate in the original 8051 design. In the cc1111, this
+ isn't true—they all live in a single unified 64kB address
+ space, and so it's possible to convert any address into a
+ unique 16-bit address. SDCC doesn't know this, and so a
+ 'global' address to SDCC consumes 3 bytes of memory, 1 byte as
+ a tag indicating the memory space and 2 bytes of offset within
+ that space. AltOS avoids these 3-byte addresses as much as
+ possible; using them involves a function call per byte
+ access. The result is that nearly every variable declaration
+ is decorated with a memory space identifier which clutters the
+ code but makes the resulting code far smaller and more
+ efficient.
+ </para>
+ <variablelist>
+ <title>SDCC 8051 memory spaces</title>
+ <varlistentry>
+ <term>__data</term>
+ <listitem>
+ <para>
+ The 8051 can directly address these 128 bytes of
+ memory. This makes them precious so they should be
+ reserved for frequently addressed values. Oh, just to
+ confuse things further, the 8 general registers in the
+ CPU are actually stored in this memory space. There are
+ magic instructions to 'bank switch' among 4 banks of
+ these registers located at 0x00 - 0x1F. AltOS uses only
+ the first bank at 0x00 - 0x07, leaving the other 24
+ bytes available for other data.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>__idata</term>
+ <listitem>
+ <para>
+ There are an additional 128 bytes of internal memory
+ that share the same address space as __data but which
+ cannot be directly addressed. The stack normally
+ occupies this space and so AltOS doesn't place any
+ static storage here.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>__xdata</term>
+ <listitem>
+ <para>
+ This is additional general memory accessed through a
+ single 16-bit address register. The CC1111F32 has 32kB
+ of memory available here. Most program data should live
+ in this memory space.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>__pdata</term>
+ <listitem>
+ <para>
+ This is an alias for the first 256 bytes of __xdata
+ memory, but uses a shorter addressing mode with
+ single global 8-bit value for the high 8 bits of the
+ address and any of several 8-bit registers for the low 8
+ bits. AltOS uses a few bits of this memory, it should
+ probably use more.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>__code</term>
+ <listitem>
+ <para>
+ All executable code must live in this address space, but
+ you can stick read-only data here too. It is addressed
+ using the 16-bit address register and special 'code'
+ access opcodes. Anything read-only should live in this space.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>__bit</term>
+ <listitem>
+ <para>
+ The 8051 has 128 bits of bit-addressible memory that
+ lives in the __data segment from 0x20 through
+ 0x2f. Special instructions access these bits
+ in a single atomic operation. This isn't so much a
+ separate address space as a special addressing mode for
+ a few bytes in the __data segment.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>__sfr, __sfr16, __sfr32, __sbit</term>
+ <listitem>
+ <para>
+ Access to physical registers in the device use this mode
+ which declares the variable name, it's type and the
+ address it lives at. No memory is allocated for these
+ variables.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </section>
+ <section>
+ <title>Function calls on the 8051</title>
+ <para>
+ Because stack addressing is expensive, and stack space
+ limited, the default function call declaration in SDCC
+ allocates all parameters and local variables in static global
+ memory. Just like fortran. This makes these functions
+ non-reentrant, and also consume space for parameters and
+ locals even when they are not running. The benefit is smaller
+ code and faster execution.
+ </para>
+ <section>
+ <title>__reentrant functions</title>
+ <para>
+ All functions which are re-entrant, either due to recursion
+ or due to a potential context switch while executing, should
+ be marked as __reentrant so that their parameters and local
+ variables get allocated on the stack. This ensures that
+ these values are not overwritten by another invocation of
+ the function.
+ </para>
+ <para>
+ Functions which use significant amounts of space for
+ arguments and/or local variables and which are not often
+ invoked can also be marked as __reentrant. The resulting
+ code will be larger, but the savings in memory are
+ frequently worthwhile.
+ </para>
+ </section>
+ <section>
+ <title>Non __reentrant functions</title>
+ <para>
+ All parameters and locals in non-reentrant functions can
+ have data space decoration so that they are allocated in
+ __xdata, __pdata or __data space as desired. This can avoid
+ consuming __data space for infrequently used variables in
+ frequently used functions.
+ </para>
+ <para>
+ All library functions called by SDCC, including functions
+ for multiplying and dividing large data types, are
+ non-reentrant. Because of this, interrupt handlers must not
+ invoke any library functions, including the multiply and
+ divide code.
+ </para>
+ </section>
+ <section>
+ <title>__interrupt functions</title>
+ <para>
+ Interrupt functions are declared with with an __interrupt
+ decoration that includes the interrupt number. SDCC saves
+ and restores all of the registers in these functions and
+ uses the 'reti' instruction at the end so that they operate
+ as stand-alone interrupt handlers. Interrupt functions may
+ call the ao_wakeup function to wake AltOS tasks.
+ </para>
+ </section>
+ <section>
+ <title>__critical functions and statements</title>
+ <para>
+ SDCC has built-in support for suspending interrupts during
+ critical code. Functions marked as __critical will have
+ interrupts suspended for the whole period of
+ execution. Individual statements may also be marked as
+ __critical which blocks interrupts during the execution of
+ that statement. Keeping critical sections as short as
+ possible is key to ensuring that interrupts are handled as
+ quickly as possible.
+ </para>
+ </section>
+ </section>
+ </chapter>
+ <chapter>
+ <title>Task functions</title>
+ <para>
+ This chapter documents how to create, destroy and schedule AltOS tasks.
+ </para>
+ <variablelist>
+ <title>AltOS Task Functions</title>
+ <varlistentry>
+ <term>ao_add_task</term>
+ <listitem>
+ <programlisting>
+void
+ao_add_task(__xdata struct ao_task * task,
+ void (*start)(void),
+ __code char *name);
+ </programlisting>
+ <para>
+ This initializes the statically allocated task structure,
+ assigns a name to it (not used for anything but the task
+ display), and the start address. It does not switch to the
+ new task. 'start' must not ever return; there is no place
+ to return to.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_exit</term>
+ <listitem>
+ <programlisting>
+void
+ao_exit(void)
+ </programlisting>
+ <para>
+ This terminates the current task.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_sleep</term>
+ <listitem>
+ <programlisting>
+void
+ao_sleep(__xdata void *wchan)
+ </programlisting>
+ <para>
+ This suspends the current task until 'wchan' is signaled
+ by ao_wakeup, or until the timeout, set by ao_alarm,
+ fires. If 'wchan' is signaled, ao_sleep returns 0, otherwise
+ it returns 1. This is the only way to switch to another task.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_wakeup</term>
+ <listitem>
+ <programlisting>
+void
+ao_wakeup(__xdata void *wchan)
+ </programlisting>
+ <para>
+ Wake all tasks blocked on 'wchan'. This makes them
+ available to be run again, but does not actually switch
+ to another task.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_alarm</term>
+ <listitem>
+ <programlisting>
+void
+ao_alarm(uint16_t delay)
+ </programlisting>
+ <para>
+ Schedules an alarm to fire in at least 'delay' ticks. If
+ the task is asleep when the alarm fires, it will wakeup
+ and ao_sleep will return 1.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_wake_task</term>
+ <listitem>
+ <programlisting>
+void
+ao_wake_task(__xdata struct ao_task *task)
+ </programlisting>
+ <para>
+ Force a specific task to wake up, independent of which
+ 'wchan' it is waiting for.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_start_scheduler</term>
+ <listitem>
+ <programlisting>
+void
+ao_start_scheduler(void)
+ </programlisting>
+ <para>
+ This is called from 'main' when the system is all
+ initialized and ready to run. It will not return.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_clock_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_clock_init(void)
+ </programlisting>
+ <para>
+ This turns on the external 48MHz clock then switches the
+ hardware to using it. This is required by many of the
+ internal devices like USB. It should be called by the
+ 'main' function first, before initializing any of the
+ other devices in the system.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>Timer Functions</title>
+ <para>
+ AltOS sets up one of the cc1111 timers to run at 100Hz and
+ exposes this tick as the fundemental unit of time. At each
+ interrupt, AltOS increments the counter, and schedules any tasks
+ waiting for that time to pass, then fires off the ADC system to
+ collect current data readings. Doing this from the ISR ensures
+ that the ADC values are sampled at a regular rate, independent
+ of any scheduling jitter.
+ </para>
+ <variablelist>
+ <title>AltOS Timer Functions</title>
+ <varlistentry>
+ <term>ao_time</term>
+ <listitem>
+ <programlisting>
+uint16_t
+ao_time(void)
+ </programlisting>
+ <para>
+ Returns the current system tick count. Note that this is
+ only a 16 bit value, and so it wraps every 655.36 seconds.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_delay</term>
+ <listitem>
+ <programlisting>
+void
+ao_delay(uint16_t ticks);
+ </programlisting>
+ <para>
+ Suspend the current task for at least 'ticks' clock units.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_timer_set_adc_interval</term>
+ <listitem>
+ <programlisting>
+void
+ao_timer_set_adc_interval(uint8_t interval);
+ </programlisting>
+ <para>
+ This sets the number of ticks between ADC samples. If set
+ to 0, no ADC samples are generated. AltOS uses this to
+ slow down the ADC sampling rate to save power.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_timer_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_timer_init(void)
+ </programlisting>
+ <para>
+ This turns on the 100Hz tick using the CC1111 timer 1. It
+ is required for any of the time-based functions to
+ work. It should be called by 'main' before ao_start_scheduler.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>AltOS Mutexes</title>
+ <para>
+ AltOS provides mutexes as a basic synchronization primitive. Each
+ mutexes is simply a byte of memory which holds 0 when the mutex
+ is free or the task id of the owning task when the mutex is
+ owned. Mutex calls are checked—attempting to acquire a mutex
+ already held by the current task or releasing a mutex not held
+ by the current task will both cause a panic.
+ </para>
+ <variablelist>
+ <title>Mutex Functions</title>
+ <varlistentry>
+ <term>ao_mutex_get</term>
+ <listitem>
+ <programlisting>
+void
+ao_mutex_get(__xdata uint8_t *mutex);
+ </programlisting>
+ <para>
+ Acquires the specified mutex, blocking if the mutex is
+ owned by another task.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_mutex_put</term>
+ <listitem>
+ <programlisting>
+void
+ao_mutex_put(__xdata uint8_t *mutex);
+ </programlisting>
+ <para>
+ Releases the specified mutex, waking up all tasks waiting
+ for it.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>CC1111 DMA engine</title>
+ <para>
+ The CC1111 contains a useful bit of extra hardware in the form
+ of five programmable DMA engines. They can be configured to copy
+ data in memory, or between memory and devices (or even between
+ two devices). AltOS exposes a general interface to this hardware
+ and uses it to handle radio and SPI data.
+ </para>
+ <para>
+ Code using a DMA engine should allocate one at startup
+ time. There is no provision to free them, and if you run out,
+ AltOS will simply panic.
+ </para>
+ <para>
+ During operation, the DMA engine is initialized with the
+ transfer parameters. Then it is started, at which point it
+ awaits a suitable event to start copying data. When copying data
+ from hardware to memory, that trigger event is supplied by the
+ hardware device. When copying data from memory to hardware, the
+ transfer is usually initiated by software.
+ </para>
+ <variablelist>
+ <title>AltOS DMA functions</title>
+ <varlistentry>
+ <term>ao_dma_alloc</term>
+ <listitem>
+ <programlisting>
+uint8_t
+ao_dma_alloc(__xdata uint8_t *done)
+ </programlisting>
+ <para>
+ Allocates a DMA engine, returning the identifier. Whenever
+ this DMA engine completes a transfer. 'done' is cleared
+ when the DMA is started, and then receives the
+ AO_DMA_DONE bit on a successful transfer or the
+ AO_DMA_ABORTED bit if ao_dma_abort was called. Note that
+ it is possible to get both bits if the transfer was
+ aborted after it had finished.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_dma_set_transfer</term>
+ <listitem>
+ <programlisting>
+void
+ao_dma_set_transfer(uint8_t id,
+ void __xdata *srcaddr,
+ void __xdata *dstaddr,
+ uint16_t count,
+ uint8_t cfg0,
+ uint8_t cfg1)
+ </programlisting>
+ <para>
+ Initializes the specified dma engine to copy data
+ from 'srcaddr' to 'dstaddr' for 'count' units. cfg0 and
+ cfg1 are values directly out of the CC1111 documentation
+ and tell the DMA engine what the transfer unit size,
+ direction and step are.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_dma_start</term>
+ <listitem>
+ <programlisting>
+void
+ao_dma_start(uint8_t id);
+ </programlisting>
+ <para>
+ Arm the specified DMA engine and await a signal from
+ either hardware or software to start transferring data.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_dma_trigger</term>
+ <listitem>
+ <programlisting>
+void
+ao_dma_trigger(uint8_t id)
+ </programlisting>
+ <para>
+ Trigger the specified DMA engine to start copying data.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_dma_abort</term>
+ <listitem>
+ <programlisting>
+void
+ao_dma_abort(uint8_t id)
+ </programlisting>
+ <para>
+ Terminate any in-progress DMA transation, marking its
+ 'done' variable with the AO_DMA_ABORTED bit.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>SDCC Stdio interface</title>
+ <para>
+ AltOS offers a stdio interface over both USB and the RF packet
+ link. This provides for control of the device localy or
+ remotely. This is hooked up to the stdio functions in SDCC by
+ providing the standard putchar/getchar/flush functions. These
+ automatically multiplex the two available communication
+ channels; output is always delivered to the channel which
+ provided the most recent input.
+ </para>
+ <variablelist>
+ <title>SDCC stdio functions</title>
+ <varlistentry>
+ <term>putchar</term>
+ <listitem>
+ <programlisting>
+void
+putchar(char c)
+ </programlisting>
+ <para>
+ Delivers a single character to the current console
+ device.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>getchar</term>
+ <listitem>
+ <programlisting>
+char
+getchar(void)
+ </programlisting>
+ <para>
+ Reads a single character from any of the available
+ console devices. The current console device is set to
+ that which delivered this character. This blocks until
+ a character is available.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>flush</term>
+ <listitem>
+ <programlisting>
+void
+flush(void)
+ </programlisting>
+ <para>
+ Flushes the current console device output buffer. Any
+ pending characters will be delivered to the target device.
+xo </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_add_stdio</term>
+ <listitem>
+ <programlisting>
+void
+ao_add_stdio(char (*pollchar)(void),
+ void (*putchar)(char),
+ void (*flush)(void))
+ </programlisting>
+ <para>
+ This adds another console device to the available
+ list.
+ </para>
+ <para>
+ 'pollchar' returns either an available character or
+ AO_READ_AGAIN if none is available. Significantly, it does
+ not block. The device driver must set 'ao_stdin_ready' to
+ 1 and call ao_wakeup(&ao_stdin_ready) when it receives
+ input to tell getchar that more data is available, at
+ which point 'pollchar' will be called again.
+ </para>
+ <para>
+ 'putchar' queues a character for output, flushing if the output buffer is
+ full. It may block in this case.
+ </para>
+ <para>
+ 'flush' forces the output buffer to be flushed. It may
+ block until the buffer is delivered, but it is not
+ required to do so.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>Command line interface</title>
+ <para>
+ AltOS includes a simple command line parser which is hooked up
+ to the stdio interfaces permitting remote control of the device
+ over USB or the RF link as desired. Each command uses a single
+ character to invoke it, the remaining characters on the line are
+ available as parameters to the command.
+ </para>
+ <variablelist>
+ <title>AltOS command line parsing functions</title>
+ <varlistentry>
+ <term>ao_cmd_register</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_register(__code struct ao_cmds *cmds)
+ </programlisting>
+ <para>
+ This registers a set of commands with the command
+ parser. There is a fixed limit on the number of command
+ sets, the system will panic if too many are registered.
+ Each command is defined by a struct ao_cmds entry:
+ <programlisting>
+struct ao_cmds {
+ char cmd;
+ void (*func)(void);
+ const char *help;
+};
+ </programlisting>
+ 'cmd' is the character naming the command. 'func' is the
+ function to invoke and 'help' is a string displayed by the
+ '?' command. Syntax errors found while executing 'func'
+ should be indicated by modifying the global ao_cmd_status
+ variable with one of the following values:
+ <variablelist>
+ <varlistentry>
+ <term>ao_cmd_success</term>
+ <listitem>
+ <para>
+ The command was parsed successfully. There is no
+ need to assign this value, it is the default.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_lex_error</term>
+ <listitem>
+ <para>
+ A token in the line was invalid, such as a number
+ containing invalid characters. The low-level
+ lexing functions already assign this value as needed.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_syntax_error</term>
+ <listitem>
+ <para>
+ The command line is invalid for some reason other
+ than invalid tokens.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_lex</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_lex(void);
+ </programlisting>
+ <para>
+ This gets the next character out of the command line
+ buffer and sticks it into ao_cmd_lex_c. At the end of the
+ line, ao_cmd_lex_c will get a newline ('\n') character.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_put16</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_put16(uint16_t v);
+ </programlisting>
+ <para>
+ Writes 'v' as four hexadecimal characters.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_put8</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_put8(uint8_t v);
+ </programlisting>
+ <para>
+ Writes 'v' as two hexadecimal characters.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_white</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_white(void)
+ </programlisting>
+ <para>
+ This skips whitespace by calling ao_cmd_lex while
+ ao_cmd_lex_c is either a space or tab. It does not skip
+ any characters if ao_cmd_lex_c already non-white.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_hex</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_hex(void)
+ </programlisting>
+ <para>
+ This reads a 16-bit hexadecimal value from the command
+ line with optional leading whitespace. The resulting value
+ is stored in ao_cmd_lex_i;
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_decimal</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_decimal(void)
+ </programlisting>
+ <para>
+ This reads a 32-bit decimal value from the command
+ line with optional leading whitespace. The resulting value
+ is stored in ao_cmd_lex_u32 and the low 16 bits are stored
+ in ao_cmd_lex_i;
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_match_word</term>
+ <listitem>
+ <programlisting>
+uint8_t
+ao_match_word(__code char *word)
+ </programlisting>
+ <para>
+ This checks to make sure that 'word' occurs on the command
+ line. It does not skip leading white space. If 'word' is
+ found, then 1 is returned. Otherwise, ao_cmd_status is set to
+ ao_cmd_syntax_error and 0 is returned.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_cmd_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_cmd_init(void
+ </programlisting>
+ <para>
+ Initializes the command system, setting up the built-in
+ commands and adding a task to run the command processing
+ loop. It should be called by 'main' before ao_start_scheduler.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>CC1111 USB target device</title>
+ <para>
+ The CC1111 contains a full-speed USB target device. It can be
+ programmed to offer any kind of USB target, but to simplify
+ interactions with a variety of operating systems, AltOS provides
+ only a single target device profile, that of a USB modem which
+ has native drivers for Linux, Windows and Mac OS X. It would be
+ easy to change the code to provide an alternate target device if
+ necessary.
+ </para>
+ <para>
+ To the rest of the system, the USB device looks like a simple
+ two-way byte stream. It can be hooked into the command line
+ interface if desired, offering control of the device over the
+ USB link. Alternatively, the functions can be accessed directly
+ to provide for USB-specific I/O.
+ </para>
+ <variablelist>
+ <title>AltOS USB functions</title>
+ <varlistentry>
+ <term>ao_usb_flush</term>
+ <listitem>
+ <programlisting>
+void
+ao_usb_flush(void);
+ </programlisting>
+ <para>
+ Flushes any pending USB output. This queues an 'IN' packet
+ to be delivered to the USB host if there is pending data,
+ or if the last IN packet was full to indicate to the host
+ that there isn't any more pending data available.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_usb_putchar</term>
+ <listitem>
+ <programlisting>
+void
+ao_usb_putchar(char c);
+ </programlisting>
+ <para>
+ If there is a pending 'IN' packet awaiting delivery to the
+ host, this blocks until that has been fetched. Then, this
+ adds a byte to the pending IN packet for delivery to the
+ USB host. If the USB packet is full, this queues the 'IN'
+ packet for delivery.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_usb_pollchar</term>
+ <listitem>
+ <programlisting>
+char
+ao_usb_pollchar(void);
+ </programlisting>
+ <para>
+ If there are no characters remaining in the last 'OUT'
+ packet received, this returns AO_READ_AGAIN. Otherwise, it
+ returns the next character, reporting to the host that it
+ is ready for more data when the last character is gone.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_usb_getchar</term>
+ <listitem>
+ <programlisting>
+char
+ao_usb_getchar(void);
+ </programlisting>
+ <para>
+ This uses ao_pollchar to receive the next character,
+ blocking while ao_pollchar returns AO_READ_AGAIN.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_usb_disable</term>
+ <listitem>
+ <programlisting>
+void
+ao_usb_disable(void);
+ </programlisting>
+ <para>
+ This turns off the USB controller. It will no longer
+ respond to host requests, nor return characters. Calling
+ any of the i/o routines while the USB device is disabled
+ is undefined, and likely to break things. Disabling the
+ USB device when not needed saves power.
+ </para>
+ <para>
+ Note that neither TeleDongle nor TeleMetrum are able to
+ signal to the USB host that they have disconnected, so
+ after disabling the USB device, it's likely that the cable
+ will need to be disconnected and reconnected before it
+ will work again.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_usb_enable</term>
+ <listitem>
+ <programlisting>
+void
+ao_usb_enable(void);
+ </programlisting>
+ <para>
+ This turns the USB controller on again after it has been
+ disabled. See the note above about needing to physically
+ remove and re-insert the cable to get the host to
+ re-initialize the USB link.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_usb_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_usb_init(void);
+ </programlisting>
+ <para>
+ This turns the USB controller on, adds a task to handle
+ the control end point and adds the usb I/O functions to
+ the stdio system. Call this from main before
+ ao_start_scheduler.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>CC1111 Serial peripheral</title>
+ <para>
+ The CC1111 provides two USART peripherals. AltOS uses one for
+ asynch serial data, generally to communicate with a GPS device,
+ and the other for a SPI bus. The UART is configured to operate
+ in 8-bits, no parity, 1 stop bit framing. The default
+ configuration has clock settings for 4800, 9600 and 57600 baud
+ operation. Additional speeds can be added by computing
+ appropriate clock values.
+ </para>
+ <para>
+ To prevent loss of data, AltOS provides receive and transmit
+ fifos of 32 characters each.
+ </para>
+ <variablelist>
+ <title>AltOS serial functions</title>
+ <varlistentry>
+ <term>ao_serial_getchar</term>
+ <listitem>
+ <programlisting>
+char
+ao_serial_getchar(void);
+ </programlisting>
+ <para>
+ Returns the next character from the receive fifo, blocking
+ until a character is received if the fifo is empty.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_serial_putchar</term>
+ <listitem>
+ <programlisting>
+void
+ao_serial_putchar(char c);
+ </programlisting>
+ <para>
+ Adds a character to the transmit fifo, blocking if the
+ fifo is full. Starts transmitting characters.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_serial_drain</term>
+ <listitem>
+ <programlisting>
+void
+ao_serial_drain(void);
+ </programlisting>
+ <para>
+ Blocks until the transmit fifo is empty. Used internally
+ when changing serial speeds.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_serial_set_speed</term>
+ <listitem>
+ <programlisting>
+void
+ao_serial_set_speed(uint8_t speed);
+ </programlisting>
+ <para>
+ Changes the serial baud rate to one of
+ AO_SERIAL_SPEED_4800, AO_SERIAL_SPEED_9600 or
+ AO_SERIAL_SPEED_57600. This first flushes the transmit
+ fifo using ao_serial_drain.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_serial_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_serial_init(void)
+ </programlisting>
+ <para>
+ Initializes the serial peripheral. Call this from 'main'
+ before jumping to ao_start_scheduler. The default speed
+ setting is AO_SERIAL_SPEED_4800.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+ <chapter>
+ <title>CC1111 Radio peripheral</title>
+ <para>
+ The CC1111 radio transceiver sends and receives digital packets
+ with forward error correction and detection. The AltOS driver is
+ fairly specific to the needs of the TeleMetrum and TeleDongle
+ devices, using it for other tasks may require customization of
+ the driver itself. There are three basic modes of operation:
+ <orderedlist>
+ <listitem>
+ <para>
+ Telemetry mode. In this mode, TeleMetrum transmits telemetry
+ frames at a fixed rate. The frames are of fixed size. This
+ is strictly a one-way communication from TeleMetrum to
+ TeleDongle.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Packet mode. In this mode, the radio is used to create a
+ reliable duplex byte stream between TeleDongle and
+ TeleMetrum. This is an asymmetrical protocol with
+ TeleMetrum only transmitting in response to a packet sent
+ from TeleDongle. Thus getting data from TeleMetrum to
+ TeleDongle requires polling. The polling rate is adaptive,
+ when no data has been received for a while, the rate slows
+ down. The packets are checked at both ends and invalid
+ data are ignored.
+ </para>
+ <para>
+ On the TeleMetrum side, the packet link is hooked into the
+ stdio mechanism, providing an alternate data path for the
+ command processor. It is enabled when the unit boots up in
+ 'idle' mode.
+ </para>
+ <para>
+ On the TeleDongle side, the packet link is enabled with a
+ command; data from the stdio package is forwarded over the
+ packet link providing a connection from the USB command
+ stream to the remote TeleMetrum device.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ Radio Direction Finding mode. In this mode, TeleMetrum
+ constructs a special packet that sounds like an audio tone
+ when received by a conventional narrow-band FM
+ receiver. This is designed to provide a beacon to track
+ the device when other location mechanisms fail.
+ </para>
+ </listitem>
+ </orderedlist>
+ </para>
+ <variablelist>
+ <title>AltOS radio functions</title>
+ <varlistentry>
+ <term>ao_radio_set_telemetry</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_set_telemetry(void);
+ </programlisting>
+ <para>
+ Configures the radio to send or receive telemetry
+ packets. This includes packet length, modulation scheme and
+ other RF parameters. It does not include the base frequency
+ or channel though. Those are set at the time of transmission
+ or reception, in case the values are changed by the user.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_set_packet</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_set_packet(void);
+ </programlisting>
+ <para>
+ Configures the radio to send or receive packet data. This
+ includes packet length, modulation scheme and other RF
+ parameters. It does not include the base frequency or
+ channel though. Those are set at the time of transmission or
+ reception, in case the values are changed by the user.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_set_rdf</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_set_rdf(void);
+ </programlisting>
+ <para>
+ Configures the radio to send RDF 'packets'. An RDF 'packet'
+ is a sequence of hex 0x55 bytes sent at a base bit rate of
+ 2kbps using a 5kHz deviation. All of the error correction
+ and data whitening logic is turned off so that the resulting
+ modulation is received as a 1kHz tone by a conventional 70cm
+ FM audio receiver.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_idle</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_idle(void);
+ </programlisting>
+ <para>
+ Sets the radio device to idle mode, waiting until it reaches
+ that state. This will terminate any in-progress transmit or
+ receive operation.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_get</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_get(void);
+ </programlisting>
+ <para>
+ Acquires the radio mutex and then configures the radio
+ frequency using the global radio calibration and channel
+ values.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_put</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_put(void);
+ </programlisting>
+ <para>
+ Releases the radio mutex.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_abort</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_abort(void);
+ </programlisting>
+ <para>
+ Aborts any transmission or reception process by aborting the
+ associated DMA object and calling ao_radio_idle to terminate
+ the radio operation.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ <variablelist>
+ <title>AltOS radio telemetry functions</title>
+ <para>
+ In telemetry mode, you can send or receive a telemetry
+ packet. The data from receiving a packet also includes the RSSI
+ and status values supplied by the receiver. These are added
+ after the telemetry data.
+ </para>
+ <varlistentry>
+ <term>ao_radio_send</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_send(__xdata struct ao_telemetry *telemetry);
+ </programlisting>
+ <para>
+ This sends the specific telemetry packet, waiting for the
+ transmission to complete. The radio must have been set to
+ telemetry mode. This function calls ao_radio_get() before
+ sending, and ao_radio_put() afterwards, to correctly
+ serialize access to the radio device.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_radio_recv</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_recv(__xdata struct ao_radio_recv *radio);
+ </programlisting>
+ <para>
+ This blocks waiting for a telemetry packet to be received.
+ The radio must have been set to telemetry mode. This
+ function calls ao_radio_get() before receiving, and
+ ao_radio_put() afterwards, to correctly serialize access
+ to the radio device. This returns non-zero if a packet was
+ received, or zero if the operation was aborted (from some
+ other task calling ao_radio_abort()).
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ <variablelist>
+ <title>AltOS radio direction finding function</title>
+ <para>
+ In radio direction finding mode, there's just one function to
+ use
+ </para>
+ <varlistentry>
+ <term>ao_radio_rdf</term>
+ <listitem>
+ <programlisting>
+void
+ao_radio_rdf(int ms);
+ </programlisting>
+ <para>
+ This sends an RDF packet lasting for the specified amount
+ of time. The maximum length is 1020 ms.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ <variablelist>
+ <title>Packet mode functions</title>
+ <para>
+ Packet mode is asymmetrical and is configured at compile time
+ for either master or slave mode (but not both). The basic I/O
+ functions look the same at both ends, but the internals are
+ different, along with the initialization steps.
+ </para>
+ <varlistentry>
+ <term>ao_packet_putchar</term>
+ <listitem>
+ <programlisting>
+void
+ao_packet_putchar(char c);
+ </programlisting>
+ <para>
+ If the output queue is full, this first blocks waiting for
+ that data to be delivered. Then, queues a character for
+ packet transmission. On the master side, this will
+ transmit a packet if the output buffer is full. On the
+ slave side, any pending data will be sent the next time
+ the master polls for data.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_packet_pollchar</term>
+ <listitem>
+ <programlisting>
+char
+ao_packet_pollchar(void);
+ </programlisting>
+ <para>
+ This returns a pending input character if available,
+ otherwise returns AO_READ_AGAIN. On the master side, if
+ this empties the buffer, it triggers a poll for more data.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_packet_slave_start</term>
+ <listitem>
+ <programlisting>
+void
+ao_packet_slave_start(void);
+ </programlisting>
+ <para>
+ This is available only on the slave side and starts a task
+ to listen for packet data.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_packet_slave_stop</term>
+ <listitem>
+ <programlisting>
+void
+ao_packet_slave_stop(void);
+ </programlisting>
+ <para>
+ Disables the packet slave task, stopping the radio receiver.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_packet_slave_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_packet_slave_init(void);
+ </programlisting>
+ <para>
+ Adds the packet stdio functions to the stdio package so
+ that when packet slave mode is enabled, characters will
+ get send and received through the stdio functions.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>ao_packet_master_init</term>
+ <listitem>
+ <programlisting>
+void
+ao_packet_master_init(void);
+ </programlisting>
+ <para>
+ Adds the 'p' packet forward command to start packet mode.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </chapter>
+</book>
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