8 AltOS is a operating system built for a variety of
9 microcontrollers used in Altus Metrum devices. It has a simple
10 porting layer for each CPU while providing a convenient
11 operating enviroment for the developer. AltOS currently
12 supports three different CPUs:
14 * STM32L series from ST Microelectronics. This ARM Cortex-M3
15 based microcontroller offers low power consumption and a
16 wide variety of built-in peripherals. Altus Metrum uses this
17 in the TeleMega, MegaDongle and TeleLCO projects.
19 * CC1111 from Texas Instruments. This device includes a
20 fabulous 10mW digital RF transceiver along with an
21 8051-compatible processor core and a range of
22 peripherals. This is used in the TeleMetrum, TeleMini,
23 TeleDongle and TeleFire projects which share the need for a
24 small microcontroller and an RF interface.
26 * ATmega32U4 from Atmel. This 8-bit AVR microcontroller is one
27 of the many used to create Arduino boards. The 32U4 includes
28 a USB interface, making it easy to connect to other
29 computers. Altus Metrum used this in prototypes of the
30 TeleScience and TelePyro boards; those have been switched to
31 the STM32L which is more capable and cheaper.
33 Among the features of AltOS are:
35 * Multi-tasking. While microcontrollers often don't
36 provide separate address spaces, it's often easier to write
37 code that operates in separate threads instead of tying
38 everything into one giant event loop.
40 * Non-preemptive. This increases latency for thread
41 switching but reduces the number of places where context
42 switching can occur. It also simplifies the operating system
43 design somewhat. Nothing in the target system (rocket flight
44 control) has tight timing requirements, and so this seems like
45 a reasonable compromise.
47 * Sleep/wakeup scheduling. Taken directly from ancient
48 Unix designs, these two provide the fundemental scheduling
49 primitive within AltOS.
51 * Mutexes. As a locking primitive, mutexes are easier to
52 use than semaphores, at least in my experience.
54 * Timers. Tasks can set an alarm which will abort any
55 pending sleep, allowing operations to time-out instead of
58 The device drivers and other subsystems in AltOS are
59 conventionally enabled by invoking their _init() function from
60 the 'main' function before that calls
61 ao_start_scheduler(). These functions initialize the pin
62 assignments, add various commands to the command processor and
63 may add tasks to the scheduler to handle the device. A typical
64 main program, thus, looks like:
72 \ /* Turn on the LED until the system is stable */
73 \ ao_led_init(LEDS_AVAILABLE);
74 \ ao_led_on(AO_LED_RED);
78 \ ao_monitor_init(AO_LED_GREEN, TRUE);
79 \ ao_rssi_init(AO_LED_RED);
81 \ ao_packet_slave_init();
82 \ ao_packet_master_init();
87 \ ao_start_scheduler();
91 As you can see, a long sequence of subsystems are initialized
92 and then the scheduler is started.
94 == AltOS Porting Layer
96 AltOS provides a CPU-independent interface to various common
97 microcontroller subsystems, including GPIO pins, interrupts,
98 SPI, I2C, USB and asynchronous serial interfaces. By making
99 these CPU-independent, device drivers, generic OS and
100 application code can all be written that work on any supported
101 CPU. Many of the architecture abstraction interfaces are
102 prefixed with ao_arch.
104 === Low-level CPU operations
106 These primitive operations provide the abstraction needed to
107 run the multi-tasking framework while providing reliable
110 ==== ao_arch_block_interrupts/ao_arch_release_interrupts
114 ao_arch_block_interrupts(void);
117 ao_arch_release_interrupts(void);
120 These disable/enable interrupt delivery, they may not
121 discard any interrupts. Use these for sections of code that
122 must be atomic with respect to any code run from an
125 ==== ao_arch_save_regs, ao_arch_save_stack, ao_arch_restore_stack
129 ao_arch_save_regs(void);
132 ao_arch_save_stack(void);
135 ao_arch_restore_stack(void);
138 These provide all of the support needed to switch
139 between tasks.. ao_arch_save_regs must save all CPU
140 registers to the current stack, including the
141 interrupt enable state. ao_arch_save_stack records the
142 current stack location in the current ao_task
143 structure. ao_arch_restore_stack switches back to the
144 saved stack, restores all registers and branches to
145 the saved return address.
147 ==== ao_arch_wait_interupt
150 #define ao_arch_wait_interrupt()
153 This stops the CPU, leaving clocks and interrupts
154 enabled. When an interrupt is received, this must wake up
155 and handle the interrupt. ao_arch_wait_interrupt is entered
156 with interrupts disabled to ensure that there is no gap
157 between determining that no task wants to run and idling the
158 CPU. It must sleep the CPU, process interrupts and then
159 disable interrupts again. If the CPU doesn't have any
160 reduced power mode, this must at the least allow pending
161 interrupts to be processed.
165 These functions provide an abstract interface to configure and
166 manipulate GPIO pins.
170 These macros may be invoked at system
171 initialization time to configure pins as
172 needed for system operation. One tricky aspect
173 is that some chips provide direct access to
174 specific GPIO pins while others only provide
175 access to a whole register full of pins. To
176 support this, the GPIO macros provide both
177 port+bit and pin arguments. Simply define the
178 arguments needed for the target platform and
179 leave the others undefined.
181 ===== ao_enable_output
184 #define ao_enable_output(port, bit, pin, value)
187 Set the specified port+bit (also called 'pin')
188 for output, initializing to the specified
189 value. The macro must avoid driving the pin
190 with the opposite value if at all possible.
192 ===== ao_enable_input
195 #define ao_enable_input(port, bit, mode)
198 Sets the specified port/bit to be an input
199 pin. 'mode' is a combination of one or more of
200 the following. Note that some platforms may
201 not support the desired mode. In that case,
202 the value will not be defined so that the
203 program will fail to compile.
205 * AO_EXTI_MODE_PULL_UP. Apply a pull-up to the
206 pin; a disconnected pin will read as 1.
208 * AO_EXTI_MODE_PULL_DOWN. Apply a pull-down to
209 the pin; a disconnected pin will read as 0.
211 * 0. Don't apply either a pull-up or
212 pull-down. A disconnected pin will read an
215 ==== Reading and writing GPIO pins
217 These macros read and write individual GPIO pins.
222 #define ao_gpio_set(port, bit, pin, value)
225 Sets the specified port/bit or pin to
231 #define ao_gpio_get(port, bit, pin)
234 Returns either 1 or 0 depending on
235 whether the input to the pin is high
237 == Programming the 8051 with SDCC
239 The 8051 is a primitive 8-bit processor, designed in the mists
240 of time in as few transistors as possible. The architecture is
241 highly irregular and includes several separate memory
242 spaces. Furthermore, accessing stack variables is slow, and
243 the stack itself is of limited size. While SDCC papers over
244 the instruction set, it is not completely able to hide the
245 memory architecture from the application designer.
247 When built on other architectures, the various SDCC-specific
248 symbols are #defined as empty strings so they don't affect the
251 === 8051 memory spaces
253 The __data/__xdata/__code memory spaces below were completely
254 separate in the original 8051 design. In the cc1111, this
255 isn't true—they all live in a single unified 64kB address
256 space, and so it's possible to convert any address into a
257 unique 16-bit address. SDCC doesn't know this, and so a
258 'global' address to SDCC consumes 3 bytes of memory, 1 byte as
259 a tag indicating the memory space and 2 bytes of offset within
260 that space. AltOS avoids these 3-byte addresses as much as
261 possible; using them involves a function call per byte
262 access. The result is that nearly every variable declaration
263 is decorated with a memory space identifier which clutters the
264 code but makes the resulting code far smaller and more
269 The 8051 can directly address these 128 bytes of
270 memory. This makes them precious so they should be
271 reserved for frequently addressed values. Oh, just to
272 confuse things further, the 8 general registers in the
273 CPU are actually stored in this memory space. There are
274 magic instructions to 'bank switch' among 4 banks of
275 these registers located at 0x00 - 0x1F. AltOS uses only
276 the first bank at 0x00 - 0x07, leaving the other 24
277 bytes available for other data.
281 There are an additional 128 bytes of internal memory
282 that share the same address space as __data but which
283 cannot be directly addressed. The stack normally
284 occupies this space and so AltOS doesn't place any
289 This is additional general memory accessed through a
290 single 16-bit address register. The CC1111F32 has 32kB
291 of memory available here. Most program data should live
292 in this memory space.
296 This is an alias for the first 256 bytes of __xdata
297 memory, but uses a shorter addressing mode with
298 single global 8-bit value for the high 8 bits of the
299 address and any of several 8-bit registers for the low 8
300 bits. AltOS uses a few bits of this memory, it should
305 All executable code must live in this address space, but
306 you can stick read-only data here too. It is addressed
307 using the 16-bit address register and special 'code'
308 access opcodes. Anything read-only should live in this space.
312 The 8051 has 128 bits of bit-addressible memory that
313 lives in the __data segment from 0x20 through
314 0x2f. Special instructions access these bits
315 in a single atomic operation. This isn't so much a
316 separate address space as a special addressing mode for
317 a few bytes in the __data segment.
319 ==== __sfr, __sfr16, __sfr32, __sbit
321 Access to physical registers in the device use this mode
322 which declares the variable name, its type and the
323 address it lives at. No memory is allocated for these
326 === Function calls on the 8051
328 Because stack addressing is expensive, and stack space
329 limited, the default function call declaration in SDCC
330 allocates all parameters and local variables in static global
331 memory. Just like fortran. This makes these functions
332 non-reentrant, and also consume space for parameters and
333 locals even when they are not running. The benefit is smaller
334 code and faster execution.
336 ==== __reentrant functions
338 All functions which are re-entrant, either due to recursion
339 or due to a potential context switch while executing, should
340 be marked as __reentrant so that their parameters and local
341 variables get allocated on the stack. This ensures that
342 these values are not overwritten by another invocation of
345 Functions which use significant amounts of space for
346 arguments and/or local variables and which are not often
347 invoked can also be marked as __reentrant. The resulting
348 code will be larger, but the savings in memory are
349 frequently worthwhile.
351 ==== Non __reentrant functions
353 All parameters and locals in non-reentrant functions can
354 have data space decoration so that they are allocated in
355 __xdata, __pdata or __data space as desired. This can avoid
356 consuming __data space for infrequently used variables in
357 frequently used functions.
359 All library functions called by SDCC, including functions
360 for multiplying and dividing large data types, are
361 non-reentrant. Because of this, interrupt handlers must not
362 invoke any library functions, including the multiply and
365 ==== __interrupt functions
367 Interrupt functions are declared with with an __interrupt
368 decoration that includes the interrupt number. SDCC saves
369 and restores all of the registers in these functions and
370 uses the 'reti' instruction at the end so that they operate
371 as stand-alone interrupt handlers. Interrupt functions may
372 call the ao_wakeup function to wake AltOS tasks.
374 ==== __critical functions and statements
376 SDCC has built-in support for suspending interrupts during
377 critical code. Functions marked as __critical will have
378 interrupts suspended for the whole period of
379 execution. Individual statements may also be marked as
380 __critical which blocks interrupts during the execution of
381 that statement. Keeping critical sections as short as
382 possible is key to ensuring that interrupts are handled as
383 quickly as possible. AltOS doesn't use this form in shared
384 code as other compilers wouldn't know what to do. Use
385 ao_arch_block_interrupts and ao_arch_release_interrupts instead.
389 This chapter documents how to create, destroy and schedule
396 \ao_add_task(__xdata struct ao_task * task,
397 \ void (*start)(void),
398 \ __code char *name);
401 This initializes the statically allocated task structure,
402 assigns a name to it (not used for anything but the task
403 display), and the start address. It does not switch to the
404 new task. 'start' must not ever return; there is no place
414 This terminates the current task.
420 ao_sleep(__xdata void *wchan)
423 This suspends the current task until 'wchan' is signaled
424 by ao_wakeup, or until the timeout, set by ao_alarm,
425 fires. If 'wchan' is signaled, ao_sleep returns 0, otherwise
426 it returns 1. This is the only way to switch to another task.
428 Because ao_wakeup wakes every task waiting on a particular
429 location, ao_sleep should be used in a loop that first checks
430 the desired condition, blocks in ao_sleep and then rechecks
431 until the condition is satisfied. If the location may be
432 signaled from an interrupt handler, the code will need to
433 block interrupts around the block of code. Here's a complete
437 \ao_arch_block_interrupts();
438 \while (!ao_radio_done)
439 \ ao_sleep(&ao_radio_done);
440 \ao_arch_release_interrupts();
447 ao_wakeup(__xdata void *wchan)
450 Wake all tasks blocked on 'wchan'. This makes them
451 available to be run again, but does not actually switch
452 to another task. Here's an example of using this:
455 \if (RFIF & RFIF_IM_DONE) {
457 \ ao_wakeup(&ao_radio_done);
458 \ RFIF &= ~RFIF_IM_DONE;
462 Note that this need not block interrupts as the
463 ao_sleep block can only be run from normal mode, and
464 so this sequence can never be interrupted with
465 execution of the other sequence.
471 ao_alarm(uint16_t delay);
474 ao_clear_alarm(void);
477 Schedules an alarm to fire in at least 'delay'
478 ticks. If the task is asleep when the alarm fires, it
479 will wakeup and ao_sleep will return 1. ao_clear_alarm
480 resets any pending alarm so that it doesn't fire at
481 some arbitrary point in the future.
484 ao_alarm(ao_packet_master_delay);
485 ao_arch_block_interrupts();
486 while (!ao_radio_dma_done)
487 if (ao_sleep(&ao_radio_dma_done) != 0)
489 ao_arch_release_interrupts();
493 In this example, a timeout is set before waiting for
494 incoming radio data. If no data is received before the
495 timeout fires, ao_sleep will return 1 and then this
496 code will abort the radio receive operation.
498 === ao_start_scheduler
502 ao_start_scheduler(void);
505 This is called from 'main' when the system is all
506 initialized and ready to run. It will not return.
515 This initializes the main CPU clock and switches to it.
519 AltOS sets up one of the CPU timers to run at 100Hz and
520 exposes this tick as the fundemental unit of time. At each
521 interrupt, AltOS increments the counter, and schedules any tasks
522 waiting for that time to pass, then fires off the sensors to
523 collect current data readings. Doing this from the ISR ensures
524 that the values are sampled at a regular rate, independent
525 of any scheduling jitter.
534 Returns the current system tick count. Note that this is
535 only a 16 bit value, and so it wraps every 655.36 seconds.
541 ao_delay(uint16_t ticks);
544 Suspend the current task for at least 'ticks' clock units.
546 === ao_timer_set_adc_interval
550 ao_timer_set_adc_interval(uint8_t interval);
553 This sets the number of ticks between ADC samples. If set
554 to 0, no ADC samples are generated. AltOS uses this to
555 slow down the ADC sampling rate to save power.
564 This turns on the 100Hz tick. It is required for any of the
565 time-based functions to work. It should be called by 'main'
566 before ao_start_scheduler.
570 AltOS provides mutexes as a basic synchronization primitive. Each
571 mutexes is simply a byte of memory which holds 0 when the mutex
572 is free or the task id of the owning task when the mutex is
573 owned. Mutex calls are checked—attempting to acquire a mutex
574 already held by the current task or releasing a mutex not held
575 by the current task will both cause a panic.
581 ao_mutex_get(__xdata uint8_t *mutex);
584 Acquires the specified mutex, blocking if the mutex is
585 owned by another task.
591 ao_mutex_put(__xdata uint8_t *mutex);
594 Releases the specified mutex, waking up all tasks waiting
599 The CC1111 and STM32L both contain a useful bit of extra
600 hardware in the form of a number of programmable DMA
601 engines. They can be configured to copy data in memory, or
602 between memory and devices (or even between two devices). AltOS
603 exposes a general interface to this hardware and uses it to
604 handle both internal and external devices.
606 Because the CC1111 and STM32L DMA engines are different, the
607 interface to them is also different. As the DMA engines are
608 currently used to implement platform-specific drivers, this
611 Code using a DMA engine should allocate one at startup
612 time. There is no provision to free them, and if you run out,
613 AltOS will simply panic.
615 During operation, the DMA engine is initialized with the
616 transfer parameters. Then it is started, at which point it
617 awaits a suitable event to start copying data. When copying data
618 from hardware to memory, that trigger event is supplied by the
619 hardware device. When copying data from memory to hardware, the
620 transfer is usually initiated by software.
622 === CC1111 DMA Engine
628 ao_dma_alloc(__xdata uint8_t *done)
631 Allocate a DMA engine, returning the
632 identifier. 'done' is cleared when the DMA is
633 started, and then receives the AO_DMA_DONE bit
634 on a successful transfer or the AO_DMA_ABORTED
635 bit if ao_dma_abort was called. Note that it
636 is possible to get both bits if the transfer
637 was aborted after it had finished.
639 ==== ao_dma_set_transfer
643 ao_dma_set_transfer(uint8_t id,
644 void __xdata *srcaddr,
645 void __xdata *dstaddr,
651 Initializes the specified dma engine to copy
652 data from 'srcaddr' to 'dstaddr' for 'count'
653 units. cfg0 and cfg1 are values directly out
654 of the CC1111 documentation and tell the DMA
655 engine what the transfer unit size, direction
662 ao_dma_start(uint8_t id);
665 Arm the specified DMA engine and await a
666 signal from either hardware or software to
667 start transferring data.
673 ao_dma_trigger(uint8_t id)
676 Trigger the specified DMA engine to start
683 ao_dma_abort(uint8_t id)
686 Terminate any in-progress DMA transaction,
687 marking its 'done' variable with the
690 === STM32L DMA Engine
695 uint8_t ao_dma_done[];
698 ao_dma_alloc(uint8_t index);
701 Reserve a DMA engine for exclusive use by one
704 ==== ao_dma_set_transfer
708 ao_dma_set_transfer(uint8_t id,
715 Initializes the specified dma engine to copy
716 data between 'peripheral' and 'memory' for
717 'count' units. 'ccr' is a value directly out
718 of the STM32L documentation and tells the DMA
719 engine what the transfer unit size, direction
726 ao_dma_set_isr(uint8_t index, void (*isr)(int))
729 This sets a function to be called when the DMA
730 transfer completes in lieu of setting the
731 ao_dma_done bits. Use this when some work
732 needs to be done when the DMA finishes that
733 cannot wait until user space resumes.
739 ao_dma_start(uint8_t id);
742 Arm the specified DMA engine and await a
743 signal from either hardware or software to
744 start transferring data. 'ao_dma_done[index]'
745 is cleared when the DMA is started, and then
746 receives the AO_DMA_DONE bit on a successful
747 transfer or the AO_DMA_ABORTED bit if
748 ao_dma_abort was called. Note that it is
749 possible to get both bits if the transfer was
750 aborted after it had finished.
752 ==== ao_dma_done_transfer
756 ao_dma_done_transfer(uint8_t id);
759 Signals that a specific DMA engine is done
760 being used. This allows multiple drivers to
761 use the same DMA engine safely.
767 ao_dma_abort(uint8_t id)
770 Terminate any in-progress DMA transaction,
771 marking its 'done' variable with the
776 AltOS offers a stdio interface over USB, serial and the RF
777 packet link. This provides for control of the device locally or
778 remotely. This is hooked up to the stdio functions by providing
779 the standard putchar/getchar/flush functions. These
780 automatically multiplex the available communication channels;
781 output is always delivered to the channel which provided the
791 Delivers a single character to the current console
801 Reads a single character from any of the available
802 console devices. The current console device is set to
803 that which delivered this character. This blocks until
804 a character is available.
813 Flushes the current console device output buffer. Any
814 pending characters will be delivered to the target device.
820 ao_add_stdio(char (*pollchar)(void),
821 void (*putchar)(char),
825 This adds another console device to the available
828 'pollchar' returns either an available character or
829 AO_READ_AGAIN if none is available. Significantly, it does
830 not block. The device driver must set 'ao_stdin_ready' to
831 1 and call ao_wakeup(&ao_stdin_ready) when it receives
832 input to tell getchar that more data is available, at
833 which point 'pollchar' will be called again.
835 'putchar' queues a character for output, flushing if the output buffer is
836 full. It may block in this case.
838 'flush' forces the output buffer to be flushed. It may
839 block until the buffer is delivered, but it is not
842 == Command line interface
844 AltOS includes a simple command line parser which is hooked up
845 to the stdio interfaces permitting remote control of the
846 device over USB, serial or the RF link as desired. Each
847 command uses a single character to invoke it, the remaining
848 characters on the line are available as parameters to the
855 ao_cmd_register(__code struct ao_cmds *cmds)
858 This registers a set of commands with the command
859 parser. There is a fixed limit on the number of command
860 sets, the system will panic if too many are registered.
861 Each command is defined by a struct ao_cmds entry:
866 \ void (*func)(void);
870 'cmd' is the character naming the command. 'func' is the
871 function to invoke and 'help' is a string displayed by the
872 '?' command. Syntax errors found while executing 'func'
873 should be indicated by modifying the global ao_cmd_status
874 variable with one of the following values:
878 The command was parsed successfully. There is no need
879 to assign this value, it is the default.
883 A token in the line was invalid, such as a number
884 containing invalid characters. The low-level lexing
885 functions already assign this value as needed.
889 The command line is invalid for some reason other than
899 This gets the next character out of the command line
900 buffer and sticks it into ao_cmd_lex_c. At the end of
901 the line, ao_cmd_lex_c will get a newline ('\n')
908 ao_cmd_put16(uint16_t v);
911 Writes 'v' as four hexadecimal characters.
917 ao_cmd_put8(uint8_t v);
920 Writes 'v' as two hexadecimal characters.
929 This skips whitespace by calling ao_cmd_lex while
930 ao_cmd_lex_c is either a space or tab. It does not
931 skip any characters if ao_cmd_lex_c already non-white.
940 This reads a 16-bit hexadecimal value from the command
941 line with optional leading whitespace. The resulting
942 value is stored in ao_cmd_lex_i;
951 This reads a 32-bit decimal value from the command
952 line with optional leading whitespace. The resulting
953 value is stored in ao_cmd_lex_u32 and the low 16 bits
954 are stored in ao_cmd_lex_i;
960 ao_match_word(__code char *word)
963 This checks to make sure that 'word' occurs on the
964 command line. It does not skip leading white space. If
965 'word' is found, then 1 is returned. Otherwise,
966 ao_cmd_status is set to ao_cmd_syntax_error and 0 is
976 Initializes the command system, setting up the
977 built-in commands and adding a task to run the command
978 processing loop. It should be called by 'main' before
983 AltOS contains a full-speed USB target device driver. It can
984 be programmed to offer any kind of USB target, but to simplify
985 interactions with a variety of operating systems, AltOS
986 provides only a single target device profile, that of a USB
987 modem which has native drivers for Linux, Windows and Mac OS
988 X. It would be easy to change the code to provide an alternate
989 target device if necessary.
991 To the rest of the system, the USB device looks like a simple
992 two-way byte stream. It can be hooked into the command line
993 interface if desired, offering control of the device over the
994 USB link. Alternatively, the functions can be accessed
995 directly to provide for USB-specific I/O.
1004 Flushes any pending USB output. This queues an 'IN'
1005 packet to be delivered to the USB host if there is
1006 pending data, or if the last IN packet was full to
1007 indicate to the host that there isn't any more pending
1014 ao_usb_putchar(char c);
1017 If there is a pending 'IN' packet awaiting delivery to
1018 the host, this blocks until that has been
1019 fetched. Then, this adds a byte to the pending IN
1020 packet for delivery to the USB host. If the USB packet
1021 is full, this queues the 'IN' packet for delivery.
1027 ao_usb_pollchar(void);
1030 If there are no characters remaining in the last 'OUT'
1031 packet received, this returns
1032 AO_READ_AGAIN. Otherwise, it returns the next
1033 character, reporting to the host that it is ready for
1034 more data when the last character is gone.
1040 ao_usb_getchar(void);
1043 This uses ao_pollchar to receive the next character,
1044 blocking while ao_pollchar returns AO_READ_AGAIN.
1050 ao_usb_disable(void);
1053 This turns off the USB controller. It will no longer
1054 respond to host requests, nor return
1055 characters. Calling any of the i/o routines while the
1056 USB device is disabled is undefined, and likely to
1057 break things. Disabling the USB device when not needed
1060 Note that neither TeleDongle v0.2 nor TeleMetrum v1
1061 are able to signal to the USB host that they have
1062 disconnected, so after disabling the USB device, it's
1063 likely that the cable will need to be disconnected and
1064 reconnected before it will work again.
1070 ao_usb_enable(void);
1073 This turns the USB controller on again after it has
1074 been disabled. See the note above about needing to
1075 physically remove and re-insert the cable to get the
1076 host to re-initialize the USB link.
1085 This turns the USB controller on, adds a task to
1086 handle the control end point and adds the usb I/O
1087 functions to the stdio system. Call this from main
1088 before ao_start_scheduler.
1090 == Serial peripherals
1092 The CC1111 provides two USART peripherals. AltOS uses one for
1093 asynch serial data, generally to communicate with a GPS
1094 device, and the other for a SPI bus. The UART is configured to
1095 operate in 8-bits, no parity, 1 stop bit framing. The default
1096 configuration has clock settings for 4800, 9600 and 57600 baud
1097 operation. Additional speeds can be added by computing
1098 appropriate clock values.
1100 To prevent loss of data, AltOS provides receive and transmit
1101 fifos of 32 characters each.
1103 === ao_serial_getchar
1107 ao_serial_getchar(void);
1110 Returns the next character from the receive fifo, blocking
1111 until a character is received if the fifo is empty.
1113 === ao_serial_putchar
1117 ao_serial_putchar(char c);
1120 Adds a character to the transmit fifo, blocking if the
1121 fifo is full. Starts transmitting characters.
1127 ao_serial_drain(void);
1130 Blocks until the transmit fifo is empty. Used internally
1131 when changing serial speeds.
1133 === ao_serial_set_speed
1137 ao_serial_set_speed(uint8_t speed);
1140 Changes the serial baud rate to one of
1141 AO_SERIAL_SPEED_4800, AO_SERIAL_SPEED_9600 or
1142 AO_SERIAL_SPEED_57600. This first flushes the transmit
1143 fifo using ao_serial_drain.
1149 ao_serial_init(void)
1152 Initializes the serial peripheral. Call this from 'main'
1153 before jumping to ao_start_scheduler. The default speed
1154 setting is AO_SERIAL_SPEED_4800.
1156 == CC1111/CC1120/CC1200 Radio peripheral
1158 === Radio Introduction
1160 The CC1111, CC1120 and CC1200 radio transceiver sends
1161 and receives digital packets with forward error
1162 correction and detection. The AltOS driver is fairly
1163 specific to the needs of the TeleMetrum and TeleDongle
1164 devices, using it for other tasks may require
1165 customization of the driver itself. There are three
1166 basic modes of operation:
1168 . Telemetry mode. In this mode, TeleMetrum transmits telemetry
1169 frames at a fixed rate. The frames are of fixed size. This
1170 is strictly a one-way communication from TeleMetrum to
1173 . Packet mode. In this mode, the radio is used to create a
1174 reliable duplex byte stream between TeleDongle and
1175 TeleMetrum. This is an asymmetrical protocol with
1176 TeleMetrum only transmitting in response to a packet sent
1177 from TeleDongle. Thus getting data from TeleMetrum to
1178 TeleDongle requires polling. The polling rate is adaptive,
1179 when no data has been received for a while, the rate slows
1180 down. The packets are checked at both ends and invalid data
1183 On the TeleMetrum side, the packet link is hooked into the
1184 stdio mechanism, providing an alternate data path for the
1185 command processor. It is enabled when the unit boots up in
1188 On the TeleDongle side, the packet link is enabled with a
1189 command; data from the stdio package is forwarded over the
1190 packet link providing a connection from the USB command
1191 stream to the remote TeleMetrum device.
1193 . Radio Direction Finding mode. In this mode, TeleMetrum
1194 constructs a special packet that sounds like an audio tone
1195 when received by a conventional narrow-band FM
1196 receiver. This is designed to provide a beacon to track the
1197 device when other location mechanisms fail.
1199 === ao_radio_set_telemetry
1203 ao_radio_set_telemetry(void);
1206 Configures the radio to send or receive telemetry
1207 packets. This includes packet length, modulation scheme and
1208 other RF parameters. It does not include the base frequency
1209 or channel though. Those are set at the time of transmission
1210 or reception, in case the values are changed by the user.
1212 === ao_radio_set_packet
1216 ao_radio_set_packet(void);
1219 Configures the radio to send or receive packet data. This
1220 includes packet length, modulation scheme and other RF
1221 parameters. It does not include the base frequency or
1222 channel though. Those are set at the time of transmission or
1223 reception, in case the values are changed by the user.
1225 === ao_radio_set_rdf
1229 ao_radio_set_rdf(void);
1232 Configures the radio to send RDF 'packets'. An RDF 'packet'
1233 is a sequence of hex 0x55 bytes sent at a base bit rate of
1234 2kbps using a 5kHz deviation. All of the error correction
1235 and data whitening logic is turned off so that the resulting
1236 modulation is received as a 1kHz tone by a conventional 70cm
1243 ao_radio_idle(void);
1246 Sets the radio device to idle mode, waiting until it reaches
1247 that state. This will terminate any in-progress transmit or
1257 Acquires the radio mutex and then configures the radio
1258 frequency using the global radio calibration and channel
1268 Releases the radio mutex.
1274 ao_radio_abort(void);
1277 Aborts any transmission or reception process by aborting the
1278 associated DMA object and calling ao_radio_idle to terminate
1279 the radio operation.
1283 In telemetry mode, you can send or receive a telemetry
1284 packet. The data from receiving a packet also includes the RSSI
1285 and status values supplied by the receiver. These are added
1286 after the telemetry data.
1292 ao_radio_send(__xdata struct ao_telemetry *telemetry);
1295 This sends the specific telemetry packet, waiting for the
1296 transmission to complete. The radio must have been set to
1297 telemetry mode. This function calls ao_radio_get() before
1298 sending, and ao_radio_put() afterwards, to correctly
1299 serialize access to the radio device.
1305 ao_radio_recv(__xdata struct ao_radio_recv *radio);
1308 This blocks waiting for a telemetry packet to be received.
1309 The radio must have been set to telemetry mode. This
1310 function calls ao_radio_get() before receiving, and
1311 ao_radio_put() afterwards, to correctly serialize access
1312 to the radio device. This returns non-zero if a packet was
1313 received, or zero if the operation was aborted (from some
1314 other task calling ao_radio_abort()).
1316 === Radio Direction Finding
1318 In radio direction finding mode, there's just one function to
1325 ao_radio_rdf(int ms);
1328 This sends an RDF packet lasting for the specified amount
1329 of time. The maximum length is 1020 ms.
1331 === Radio Packet Mode
1333 Packet mode is asymmetrical and is configured at compile time
1334 for either master or slave mode (but not both). The basic I/O
1335 functions look the same at both ends, but the internals are
1336 different, along with the initialization steps.
1338 ==== ao_packet_putchar
1342 ao_packet_putchar(char c);
1345 If the output queue is full, this first blocks waiting for
1346 that data to be delivered. Then, queues a character for
1347 packet transmission. On the master side, this will
1348 transmit a packet if the output buffer is full. On the
1349 slave side, any pending data will be sent the next time
1350 the master polls for data.
1352 ==== ao_packet_pollchar
1356 ao_packet_pollchar(void);
1359 This returns a pending input character if available,
1360 otherwise returns AO_READ_AGAIN. On the master side, if
1361 this empties the buffer, it triggers a poll for more data.
1363 ==== ao_packet_slave_start
1367 ao_packet_slave_start(void);
1370 This is available only on the slave side and starts a task
1371 to listen for packet data.
1373 ==== ao_packet_slave_stop
1377 ao_packet_slave_stop(void);
1380 Disables the packet slave task, stopping the radio receiver.
1382 ==== ao_packet_slave_init
1386 ao_packet_slave_init(void);
1389 Adds the packet stdio functions to the stdio package so
1390 that when packet slave mode is enabled, characters will
1391 get send and received through the stdio functions.
1393 ==== ao_packet_master_init
1397 ao_packet_master_init(void);
1400 Adds the 'p' packet forward command to start packet mode.
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