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7 <subtitle>Altos Metrum Operating System</subtitle>
10 <firstname>Keith</firstname>
11 <surname>Packard</surname>
15 <holder>Keith Packard</holder>
19 This document is released under the terms of the
20 <ulink url="http://creativecommons.org/licenses/by-sa/3.0/">
21 Creative Commons ShareAlike 3.0
28 <revnumber>0.1</revnumber>
29 <date>22 November 2010</date>
30 <revremark>Initial content</revremark>
35 <title>Overview</title>
37 AltOS is a operating system built for the 8051-compatible
38 processor found in the TI cc1111 microcontroller. It's designed
39 to be small and easy to program with. The main features are:
42 <para>Multi-tasking. While the 8051 doesn't provide separate
43 address spaces, it's often easier to write code that operates
44 in separate threads instead of tying everything into one giant
49 <para>Non-preemptive. This increases latency for thread
50 switching but reduces the number of places where context
51 switching can occur. It also simplifies the operating system
52 design somewhat. Nothing in the target system (rocket flight
53 control) has tight timing requirements, and so this seems like
54 a reasonable compromise.
58 <para>Sleep/wakeup scheduling. Taken directly from ancient
59 Unix designs, these two provide the fundemental scheduling
60 primitive within AltOS.
64 <para>Mutexes. As a locking primitive, mutexes are easier to
65 use than semaphores, at least in my experience.
69 <para>Timers. Tasks can set an alarm which will abort any
70 pending sleep, allowing operations to time-out instead of
77 The device drivers and other subsystems in AltOS are
78 conventionally enabled by invoking their _init() function from
79 the 'main' function before that calls
80 ao_start_scheduler(). These functions initialize the pin
81 assignments, add various commands to the command processor and
82 may add tasks to the scheduler to handle the device. A typical
83 main program, thus, looks like:
90 /* Turn on the LED until the system is stable */
91 ao_led_init(LEDS_AVAILABLE);
92 ao_led_on(AO_LED_RED);
96 ao_monitor_init(AO_LED_GREEN, TRUE);
97 ao_rssi_init(AO_LED_RED);
99 ao_packet_slave_init();
100 ao_packet_master_init();
105 ao_start_scheduler();
108 As you can see, a long sequence of subsystems are initialized
109 and then the scheduler is started.
113 <title>Programming the 8051 with SDCC</title>
115 The 8051 is a primitive 8-bit processor, designed in the mists
116 of time in as few transistors as possible. The architecture is
117 highly irregular and includes several separate memory
118 spaces. Furthermore, accessing stack variables is slow, and the
119 stack itself is of limited size. While SDCC papers over the
120 instruction set, it is not completely able to hide the memory
121 architecture from the application designer.
124 <title>8051 memory spaces</title>
126 The __data/__xdata/__code memory spaces below were completely
127 separate in the original 8051 design. In the cc1111, this
128 isn't true—they all live in a single unified 64kB address
129 space, and so it's possible to convert any address into a
130 unique 16-bit address. SDCC doesn't know this, and so a
131 'global' address to SDCC consumes 3 bytes of memory, 1 byte as
132 a tag indicating the memory space and 2 bytes of offset within
133 that space. AltOS avoids these 3-byte addresses as much as
134 possible; using them involves a function call per byte
135 access. The result is that nearly every variable declaration
136 is decorated with a memory space identifier which clutters the
137 code but makes the resulting code far smaller and more
141 <title>__data</title>
143 The 8051 can directly address these 128 bytes of
144 memory. This makes them precious so they should be
145 reserved for frequently addressed values. Oh, just to
146 confuse things further, the 8 general registers in the
147 CPU are actually stored in this memory space. There are
148 magic instructions to 'bank switch' among 4 banks of
149 these registers located at 0x00 - 0x1F. AltOS uses only
150 the first bank at 0x00 - 0x07, leaving the other 24
151 bytes available for other data.
155 <title>__idata</title>
157 There are an additional 128 bytes of internal memory
158 that share the same address space as __data but which
159 cannot be directly addressed. The stack normally
160 occupies this space and so AltOS doesn't place any
165 <title>__xdata</title>
167 This is additional general memory accessed through a
168 single 16-bit address register. The CC1111F32 has 32kB
169 of memory available here. Most program data should live
170 in this memory space.
174 <title>__pdata</title>
176 This is an alias for the first 256 bytes of __xdata
177 memory, but uses a shorter addressing mode with
178 single global 8-bit value for the high 8 bits of the
179 address and any of several 8-bit registers for the low 8
180 bits. AltOS uses a few bits of this memory, it should
185 <title>__code</title>
187 All executable code must live in this address space, but
188 you can stick read-only data here too. It is addressed
189 using the 16-bit address register and special 'code'
190 access opcodes. Anything read-only should live in this space.
196 The 8051 has 128 bits of bit-addressible memory that
197 lives in the __data segment from 0x20 through
198 0x2f. Special instructions access these bits
199 in a single atomic operation. This isn't so much a
200 separate address space as a special addressing mode for
201 a few bytes in the __data segment.
205 <title>__sfr, __sfr16, __sfr32, __sbit</title>
207 Access to physical registers in the device use this mode
208 which declares the variable name, it's type and the
209 address it lives at. No memory is allocated for these
215 <title>Function calls on the 8051</title>
217 Because stack addressing is expensive, and stack space
218 limited, the default function call declaration in SDCC
219 allocates all parameters and local variables in static global
220 memory. Just like fortran. This makes these functions
221 non-reentrant, and also consume space for parameters and
222 locals even when they are not running. The benefit is smaller
223 code and faster execution.
226 <title>__reentrant functions</title>
228 All functions which are re-entrant, either due to recursion
229 or due to a potential context switch while executing, should
230 be marked as __reentrant so that their parameters and local
231 variables get allocated on the stack. This ensures that
232 these values are not overwritten by another invocation of
236 Functions which use significant amounts of space for
237 arguments and/or local variables and which are not often
238 invoked can also be marked as __reentrant. The resulting
239 code will be larger, but the savings in memory are
240 frequently worthwhile.
244 <title>Non __reentrant functions</title>
246 All parameters and locals in non-reentrant functions can
247 have data space decoration so that they are allocated in
248 __xdata, __pdata or __data space as desired. This can avoid
249 consuming __data space for infrequently used variables in
250 frequently used functions.
253 All library functions called by SDCC, including functions
254 for multiplying and dividing large data types, are
255 non-reentrant. Because of this, interrupt handlers must not
256 invoke any library functions, including the multiply and
261 <title>__interrupt functions</title>
263 Interrupt functions are declared with with an __interrupt
264 decoration that includes the interrupt number. SDCC saves
265 and restores all of the registers in these functions and
266 uses the 'reti' instruction at the end so that they operate
267 as stand-alone interrupt handlers. Interrupt functions may
268 call the ao_wakeup function to wake AltOS tasks.
272 <title>__critical functions and statements</title>
274 SDCC has built-in support for suspending interrupts during
275 critical code. Functions marked as __critical will have
276 interrupts suspended for the whole period of
277 execution. Individual statements may also be marked as
278 __critical which blocks interrupts during the execution of
279 that statement. Keeping critical sections as short as
280 possible is key to ensuring that interrupts are handled as
287 <title>Task functions</title>
289 This chapter documents how to create, destroy and schedule AltOS tasks.
292 <title>ao_add_task</title>
295 ao_add_task(__xdata struct ao_task * task,
300 This initializes the statically allocated task structure,
301 assigns a name to it (not used for anything but the task
302 display), and the start address. It does not switch to the
303 new task. 'start' must not ever return; there is no place
308 <title>ao_exit</title>
314 This terminates the current task.
318 <title>ao_sleep</title>
321 ao_sleep(__xdata void *wchan)
324 This suspends the current task until 'wchan' is signaled
325 by ao_wakeup, or until the timeout, set by ao_alarm,
326 fires. If 'wchan' is signaled, ao_sleep returns 0, otherwise
327 it returns 1. This is the only way to switch to another task.
330 Because ao_wakeup wakes every task waiting on a particular
331 location, ao_sleep should be used in a loop that first
332 checks the desired condition, blocks in ao_sleep and then
333 rechecks until the condition is satisfied. If the
334 location may be signaled from an interrupt handler, the
335 code will need to block interrupts by using the __critical
336 label around the block of code. Here's a complete example:
338 __critical while (!ao_radio_done)
339 ao_sleep(&ao_radio_done);
344 <title>ao_wakeup</title>
347 ao_wakeup(__xdata void *wchan)
350 Wake all tasks blocked on 'wchan'. This makes them
351 available to be run again, but does not actually switch
352 to another task. Here's an example of using this:
354 if (RFIF & RFIF_IM_DONE) {
356 ao_wakeup(&ao_radio_done);
357 RFIF &= ~RFIF_IM_DONE;
360 Note that this need not be enclosed in __critical as the
361 ao_sleep block can only be run from normal mode, and so
362 this sequence can never be interrupted with execution of
367 <title>ao_alarm</title>
370 ao_alarm(uint16_t delay)
373 Schedules an alarm to fire in at least 'delay' ticks. If
374 the task is asleep when the alarm fires, it will wakeup
375 and ao_sleep will return 1.
377 ao_alarm(ao_packet_master_delay);
378 __critical while (!ao_radio_dma_done)
379 if (ao_sleep(&ao_radio_dma_done) != 0)
382 In this example, a timeout is set before waiting for
383 incoming radio data. If no data is received before the
384 timeout fires, ao_sleep will return 1 and then this code
385 will abort the radio receive operation.
389 <title>ao_start_scheduler</title>
392 ao_start_scheduler(void)
395 This is called from 'main' when the system is all
396 initialized and ready to run. It will not return.
400 <title>ao_clock_init</title>
406 This turns on the external 48MHz clock then switches the
407 hardware to using it. This is required by many of the
408 internal devices like USB. It should be called by the
409 'main' function first, before initializing any of the
410 other devices in the system.
415 <title>Timer Functions</title>
417 AltOS sets up one of the cc1111 timers to run at 100Hz and
418 exposes this tick as the fundemental unit of time. At each
419 interrupt, AltOS increments the counter, and schedules any tasks
420 waiting for that time to pass, then fires off the ADC system to
421 collect current data readings. Doing this from the ISR ensures
422 that the ADC values are sampled at a regular rate, independent
423 of any scheduling jitter.
426 <title>ao_time</title>
432 Returns the current system tick count. Note that this is
433 only a 16 bit value, and so it wraps every 655.36 seconds.
437 <title>ao_delay</title>
440 ao_delay(uint16_t ticks);
443 Suspend the current task for at least 'ticks' clock units.
447 <title>ao_timer_set_adc_interval</title>
450 ao_timer_set_adc_interval(uint8_t interval);
453 This sets the number of ticks between ADC samples. If set
454 to 0, no ADC samples are generated. AltOS uses this to
455 slow down the ADC sampling rate to save power.
459 <title>ao_timer_init</title>
465 This turns on the 100Hz tick using the CC1111 timer 1. It
466 is required for any of the time-based functions to
467 work. It should be called by 'main' before ao_start_scheduler.
472 <title>AltOS Mutexes</title>
474 AltOS provides mutexes as a basic synchronization primitive. Each
475 mutexes is simply a byte of memory which holds 0 when the mutex
476 is free or the task id of the owning task when the mutex is
477 owned. Mutex calls are checked—attempting to acquire a mutex
478 already held by the current task or releasing a mutex not held
479 by the current task will both cause a panic.
482 <title>ao_mutex_get</title>
485 ao_mutex_get(__xdata uint8_t *mutex);
488 Acquires the specified mutex, blocking if the mutex is
489 owned by another task.
493 <title>ao_mutex_put</title>
496 ao_mutex_put(__xdata uint8_t *mutex);
499 Releases the specified mutex, waking up all tasks waiting
505 <title>CC1111 DMA engine</title>
507 The CC1111 contains a useful bit of extra hardware in the form
508 of five programmable DMA engines. They can be configured to copy
509 data in memory, or between memory and devices (or even between
510 two devices). AltOS exposes a general interface to this hardware
511 and uses it to handle radio and SPI data.
514 Code using a DMA engine should allocate one at startup
515 time. There is no provision to free them, and if you run out,
516 AltOS will simply panic.
519 During operation, the DMA engine is initialized with the
520 transfer parameters. Then it is started, at which point it
521 awaits a suitable event to start copying data. When copying data
522 from hardware to memory, that trigger event is supplied by the
523 hardware device. When copying data from memory to hardware, the
524 transfer is usually initiated by software.
527 <title>ao_dma_alloc</title>
530 ao_dma_alloc(__xdata uint8_t *done)
533 Allocates a DMA engine, returning the identifier. Whenever
534 this DMA engine completes a transfer. 'done' is cleared
535 when the DMA is started, and then receives the
536 AO_DMA_DONE bit on a successful transfer or the
537 AO_DMA_ABORTED bit if ao_dma_abort was called. Note that
538 it is possible to get both bits if the transfer was
539 aborted after it had finished.
543 <title>ao_dma_set_transfer</title>
546 ao_dma_set_transfer(uint8_t id,
547 void __xdata *srcaddr,
548 void __xdata *dstaddr,
554 Initializes the specified dma engine to copy data
555 from 'srcaddr' to 'dstaddr' for 'count' units. cfg0 and
556 cfg1 are values directly out of the CC1111 documentation
557 and tell the DMA engine what the transfer unit size,
558 direction and step are.
562 <title>ao_dma_start</title>
565 ao_dma_start(uint8_t id);
568 Arm the specified DMA engine and await a signal from
569 either hardware or software to start transferring data.
573 <title>ao_dma_trigger</title>
576 ao_dma_trigger(uint8_t id)
579 Trigger the specified DMA engine to start copying data.
583 <title>ao_dma_abort</title>
586 ao_dma_abort(uint8_t id)
589 Terminate any in-progress DMA transation, marking its
590 'done' variable with the AO_DMA_ABORTED bit.
595 <title>SDCC Stdio interface</title>
597 AltOS offers a stdio interface over both USB and the RF packet
598 link. This provides for control of the device localy or
599 remotely. This is hooked up to the stdio functions in SDCC by
600 providing the standard putchar/getchar/flush functions. These
601 automatically multiplex the two available communication
602 channels; output is always delivered to the channel which
603 provided the most recent input.
606 <title>putchar</title>
612 Delivers a single character to the current console
617 <title>getchar</title>
623 Reads a single character from any of the available
624 console devices. The current console device is set to
625 that which delivered this character. This blocks until
626 a character is available.
636 Flushes the current console device output buffer. Any
637 pending characters will be delivered to the target device.
641 <title>ao_add_stdio</title>
644 ao_add_stdio(char (*pollchar)(void),
645 void (*putchar)(char),
649 This adds another console device to the available
653 'pollchar' returns either an available character or
654 AO_READ_AGAIN if none is available. Significantly, it does
655 not block. The device driver must set 'ao_stdin_ready' to
656 1 and call ao_wakeup(&ao_stdin_ready) when it receives
657 input to tell getchar that more data is available, at
658 which point 'pollchar' will be called again.
661 'putchar' queues a character for output, flushing if the output buffer is
662 full. It may block in this case.
665 'flush' forces the output buffer to be flushed. It may
666 block until the buffer is delivered, but it is not
672 <title>Command line interface</title>
674 AltOS includes a simple command line parser which is hooked up
675 to the stdio interfaces permitting remote control of the device
676 over USB or the RF link as desired. Each command uses a single
677 character to invoke it, the remaining characters on the line are
678 available as parameters to the command.
681 <title>ao_cmd_register</title>
684 ao_cmd_register(__code struct ao_cmds *cmds)
687 This registers a set of commands with the command
688 parser. There is a fixed limit on the number of command
689 sets, the system will panic if too many are registered.
690 Each command is defined by a struct ao_cmds entry:
698 'cmd' is the character naming the command. 'func' is the
699 function to invoke and 'help' is a string displayed by the
700 '?' command. Syntax errors found while executing 'func'
701 should be indicated by modifying the global ao_cmd_status
702 variable with one of the following values:
705 <title>ao_cmd_success</title>
708 The command was parsed successfully. There is no
709 need to assign this value, it is the default.
714 <title>ao_cmd_lex_error</title>
717 A token in the line was invalid, such as a number
718 containing invalid characters. The low-level
719 lexing functions already assign this value as needed.
724 <title>ao_syntax_error</title>
727 The command line is invalid for some reason other
736 <title>ao_cmd_lex</title>
742 This gets the next character out of the command line
743 buffer and sticks it into ao_cmd_lex_c. At the end of the
744 line, ao_cmd_lex_c will get a newline ('\n') character.
748 <title>ao_cmd_put16</title>
751 ao_cmd_put16(uint16_t v);
754 Writes 'v' as four hexadecimal characters.
758 <title>ao_cmd_put8</title>
761 ao_cmd_put8(uint8_t v);
764 Writes 'v' as two hexadecimal characters.
768 <title>ao_cmd_white</title>
774 This skips whitespace by calling ao_cmd_lex while
775 ao_cmd_lex_c is either a space or tab. It does not skip
776 any characters if ao_cmd_lex_c already non-white.
780 <title>ao_cmd_hex</title>
786 This reads a 16-bit hexadecimal value from the command
787 line with optional leading whitespace. The resulting value
788 is stored in ao_cmd_lex_i;
792 <title>ao_cmd_decimal</title>
798 This reads a 32-bit decimal value from the command
799 line with optional leading whitespace. The resulting value
800 is stored in ao_cmd_lex_u32 and the low 16 bits are stored
805 <title>ao_match_word</title>
808 ao_match_word(__code char *word)
811 This checks to make sure that 'word' occurs on the command
812 line. It does not skip leading white space. If 'word' is
813 found, then 1 is returned. Otherwise, ao_cmd_status is set to
814 ao_cmd_syntax_error and 0 is returned.
818 <title>ao_cmd_init</title>
824 Initializes the command system, setting up the built-in
825 commands and adding a task to run the command processing
826 loop. It should be called by 'main' before ao_start_scheduler.
831 <title>CC1111 USB target device</title>
833 The CC1111 contains a full-speed USB target device. It can be
834 programmed to offer any kind of USB target, but to simplify
835 interactions with a variety of operating systems, AltOS provides
836 only a single target device profile, that of a USB modem which
837 has native drivers for Linux, Windows and Mac OS X. It would be
838 easy to change the code to provide an alternate target device if
842 To the rest of the system, the USB device looks like a simple
843 two-way byte stream. It can be hooked into the command line
844 interface if desired, offering control of the device over the
845 USB link. Alternatively, the functions can be accessed directly
846 to provide for USB-specific I/O.
849 <title>ao_usb_flush</title>
855 Flushes any pending USB output. This queues an 'IN' packet
856 to be delivered to the USB host if there is pending data,
857 or if the last IN packet was full to indicate to the host
858 that there isn't any more pending data available.
862 <title>ao_usb_putchar</title>
865 ao_usb_putchar(char c);
868 If there is a pending 'IN' packet awaiting delivery to the
869 host, this blocks until that has been fetched. Then, this
870 adds a byte to the pending IN packet for delivery to the
871 USB host. If the USB packet is full, this queues the 'IN'
876 <title>ao_usb_pollchar</title>
879 ao_usb_pollchar(void);
882 If there are no characters remaining in the last 'OUT'
883 packet received, this returns AO_READ_AGAIN. Otherwise, it
884 returns the next character, reporting to the host that it
885 is ready for more data when the last character is gone.
889 <title>ao_usb_getchar</title>
892 ao_usb_getchar(void);
895 This uses ao_pollchar to receive the next character,
896 blocking while ao_pollchar returns AO_READ_AGAIN.
900 <title>ao_usb_disable</title>
903 ao_usb_disable(void);
906 This turns off the USB controller. It will no longer
907 respond to host requests, nor return characters. Calling
908 any of the i/o routines while the USB device is disabled
909 is undefined, and likely to break things. Disabling the
910 USB device when not needed saves power.
913 Note that neither TeleDongle nor TeleMetrum are able to
914 signal to the USB host that they have disconnected, so
915 after disabling the USB device, it's likely that the cable
916 will need to be disconnected and reconnected before it
921 <title>ao_usb_enable</title>
927 This turns the USB controller on again after it has been
928 disabled. See the note above about needing to physically
929 remove and re-insert the cable to get the host to
930 re-initialize the USB link.
934 <title>ao_usb_init</title>
940 This turns the USB controller on, adds a task to handle
941 the control end point and adds the usb I/O functions to
942 the stdio system. Call this from main before
948 <title>CC1111 Serial peripheral</title>
950 The CC1111 provides two USART peripherals. AltOS uses one for
951 asynch serial data, generally to communicate with a GPS device,
952 and the other for a SPI bus. The UART is configured to operate
953 in 8-bits, no parity, 1 stop bit framing. The default
954 configuration has clock settings for 4800, 9600 and 57600 baud
955 operation. Additional speeds can be added by computing
956 appropriate clock values.
959 To prevent loss of data, AltOS provides receive and transmit
960 fifos of 32 characters each.
963 <title>ao_serial_getchar</title>
966 ao_serial_getchar(void);
969 Returns the next character from the receive fifo, blocking
970 until a character is received if the fifo is empty.
974 <title>ao_serial_putchar</title>
977 ao_serial_putchar(char c);
980 Adds a character to the transmit fifo, blocking if the
981 fifo is full. Starts transmitting characters.
985 <title>ao_serial_drain</title>
988 ao_serial_drain(void);
991 Blocks until the transmit fifo is empty. Used internally
992 when changing serial speeds.
996 <title>ao_serial_set_speed</title>
999 ao_serial_set_speed(uint8_t speed);
1002 Changes the serial baud rate to one of
1003 AO_SERIAL_SPEED_4800, AO_SERIAL_SPEED_9600 or
1004 AO_SERIAL_SPEED_57600. This first flushes the transmit
1005 fifo using ao_serial_drain.
1009 <title>ao_serial_init</title>
1012 ao_serial_init(void)
1015 Initializes the serial peripheral. Call this from 'main'
1016 before jumping to ao_start_scheduler. The default speed
1017 setting is AO_SERIAL_SPEED_4800.
1022 <title>CC1111 Radio peripheral</title>
1024 The CC1111 radio transceiver sends and receives digital packets
1025 with forward error correction and detection. The AltOS driver is
1026 fairly specific to the needs of the TeleMetrum and TeleDongle
1027 devices, using it for other tasks may require customization of
1028 the driver itself. There are three basic modes of operation:
1032 Telemetry mode. In this mode, TeleMetrum transmits telemetry
1033 frames at a fixed rate. The frames are of fixed size. This
1034 is strictly a one-way communication from TeleMetrum to
1040 Packet mode. In this mode, the radio is used to create a
1041 reliable duplex byte stream between TeleDongle and
1042 TeleMetrum. This is an asymmetrical protocol with
1043 TeleMetrum only transmitting in response to a packet sent
1044 from TeleDongle. Thus getting data from TeleMetrum to
1045 TeleDongle requires polling. The polling rate is adaptive,
1046 when no data has been received for a while, the rate slows
1047 down. The packets are checked at both ends and invalid
1051 On the TeleMetrum side, the packet link is hooked into the
1052 stdio mechanism, providing an alternate data path for the
1053 command processor. It is enabled when the unit boots up in
1057 On the TeleDongle side, the packet link is enabled with a
1058 command; data from the stdio package is forwarded over the
1059 packet link providing a connection from the USB command
1060 stream to the remote TeleMetrum device.
1065 Radio Direction Finding mode. In this mode, TeleMetrum
1066 constructs a special packet that sounds like an audio tone
1067 when received by a conventional narrow-band FM
1068 receiver. This is designed to provide a beacon to track
1069 the device when other location mechanisms fail.
1075 <title>ao_radio_set_telemetry</title>
1078 ao_radio_set_telemetry(void);
1081 Configures the radio to send or receive telemetry
1082 packets. This includes packet length, modulation scheme and
1083 other RF parameters. It does not include the base frequency
1084 or channel though. Those are set at the time of transmission
1085 or reception, in case the values are changed by the user.
1089 <title>ao_radio_set_packet</title>
1092 ao_radio_set_packet(void);
1095 Configures the radio to send or receive packet data. This
1096 includes packet length, modulation scheme and other RF
1097 parameters. It does not include the base frequency or
1098 channel though. Those are set at the time of transmission or
1099 reception, in case the values are changed by the user.
1103 <title>ao_radio_set_rdf</title>
1106 ao_radio_set_rdf(void);
1109 Configures the radio to send RDF 'packets'. An RDF 'packet'
1110 is a sequence of hex 0x55 bytes sent at a base bit rate of
1111 2kbps using a 5kHz deviation. All of the error correction
1112 and data whitening logic is turned off so that the resulting
1113 modulation is received as a 1kHz tone by a conventional 70cm
1118 <title>ao_radio_idle</title>
1121 ao_radio_idle(void);
1124 Sets the radio device to idle mode, waiting until it reaches
1125 that state. This will terminate any in-progress transmit or
1130 <title>ao_radio_get</title>
1136 Acquires the radio mutex and then configures the radio
1137 frequency using the global radio calibration and channel
1142 <title>ao_radio_put</title>
1148 Releases the radio mutex.
1152 <title>ao_radio_abort</title>
1155 ao_radio_abort(void);
1158 Aborts any transmission or reception process by aborting the
1159 associated DMA object and calling ao_radio_idle to terminate
1160 the radio operation.
1164 In telemetry mode, you can send or receive a telemetry
1165 packet. The data from receiving a packet also includes the RSSI
1166 and status values supplied by the receiver. These are added
1167 after the telemetry data.
1170 <title>ao_radio_send</title>
1173 ao_radio_send(__xdata struct ao_telemetry *telemetry);
1176 This sends the specific telemetry packet, waiting for the
1177 transmission to complete. The radio must have been set to
1178 telemetry mode. This function calls ao_radio_get() before
1179 sending, and ao_radio_put() afterwards, to correctly
1180 serialize access to the radio device.
1184 <title>ao_radio_recv</title>
1187 ao_radio_recv(__xdata struct ao_radio_recv *radio);
1190 This blocks waiting for a telemetry packet to be received.
1191 The radio must have been set to telemetry mode. This
1192 function calls ao_radio_get() before receiving, and
1193 ao_radio_put() afterwards, to correctly serialize access
1194 to the radio device. This returns non-zero if a packet was
1195 received, or zero if the operation was aborted (from some
1196 other task calling ao_radio_abort()).
1200 In radio direction finding mode, there's just one function to
1204 <title>ao_radio_rdf</title>
1207 ao_radio_rdf(int ms);
1210 This sends an RDF packet lasting for the specified amount
1211 of time. The maximum length is 1020 ms.
1215 Packet mode is asymmetrical and is configured at compile time
1216 for either master or slave mode (but not both). The basic I/O
1217 functions look the same at both ends, but the internals are
1218 different, along with the initialization steps.
1221 <title>ao_packet_putchar</title>
1224 ao_packet_putchar(char c);
1227 If the output queue is full, this first blocks waiting for
1228 that data to be delivered. Then, queues a character for
1229 packet transmission. On the master side, this will
1230 transmit a packet if the output buffer is full. On the
1231 slave side, any pending data will be sent the next time
1232 the master polls for data.
1236 <title>ao_packet_pollchar</title>
1239 ao_packet_pollchar(void);
1242 This returns a pending input character if available,
1243 otherwise returns AO_READ_AGAIN. On the master side, if
1244 this empties the buffer, it triggers a poll for more data.
1248 <title>ao_packet_slave_start</title>
1251 ao_packet_slave_start(void);
1254 This is available only on the slave side and starts a task
1255 to listen for packet data.
1259 <title>ao_packet_slave_stop</title>
1262 ao_packet_slave_stop(void);
1265 Disables the packet slave task, stopping the radio receiver.
1269 <title>ao_packet_slave_init</title>
1272 ao_packet_slave_init(void);
1275 Adds the packet stdio functions to the stdio package so
1276 that when packet slave mode is enabled, characters will
1277 get send and received through the stdio functions.
1281 <title>ao_packet_master_init</title>
1284 ao_packet_master_init(void);
1287 Adds the 'p' packet forward command to start packet mode.
projects / fw / altos / blob