2 * http://ad7zj.net/kd7lmo/aprsbeacon_code.html
4 * @mainpage Pico Beacon
6 * @section overview_sec Overview
8 * The Pico Beacon is an APRS based tracking beacon that operates in the UHF 420-450MHz band. The device utilizes a
9 * Microchip PIC 18F2525 embedded controller, Motorola M12+ GPS engine, and Analog Devices AD9954 DDS. The device is capable
10 * of generating a 1200bps A-FSK and 9600 bps FSK AX.25 compliant APRS (Automatic Position Reporting System) message.
14 * @section history_sec Revision History
16 * @subsection v305 V3.05
17 * 23 Dec 2006, Change include; (1) change printf format width to conform to ANSI standard when new CCS 4.xx compiler released.
20 * @subsection v304 V3.04
21 * 10 Jan 2006, Change include; (1) added amplitude control to engineering mode,
22 * (2) corrected number of bytes reported in log,
23 * (3) add engineering command to set high rate position reports (5 seconds), and
24 * (4) corrected size of LOG_COORD block when searching for end of log.
26 * @subsection v303 V3.03
27 * 15 Sep 2005, Change include; (1) removed AD9954 setting SDIO as input pin,
28 * (2) additional comments and Doxygen tags,
29 * (3) integration and test code calculates DDS FTW,
30 * (4) swapped bus and reference analog input ports (hardware change),
31 * (5) added message that indicates we are reading flash log and reports length,
32 * (6) report bus voltage in 10mV steps, and
33 * (7) change log type enumerated values to XORed nibbles for error detection.
36 * @subsection v302 V3.02
37 * 6 Apr 2005, Change include; (1) corrected tracked satellite count in NMEA-0183 $GPGGA message,
38 * (2) Doxygen documentation clean up and additions, and
39 * (3) added integration and test code to baseline.
42 * @subsection v301 V3.01
43 * 13 Jan 2005, Renamed project and files to Pico Beacon.
46 * @subsection v300 V3.00
47 * 15 Nov 2004, Change include; (1) Micro Beacon extreme hardware changes including integral transmitter,
48 * (2) PIC18F2525 processor,
49 * (3) AD9954 DDS support functions,
50 * (4) added comments and formatting for doxygen,
51 * (5) process GPS data with native Motorola protocol,
52 * (6) generate plain text $GPGGA and $GPRMC messages,
53 * (7) power down GPS 5 hours after lock,
54 * (8) added flight data recorder, and
55 * (9) added diagnostics terminal mode.
58 * @subsection v201 V2.01
59 * 30 Jan 2004, Change include; (1) General clean up of in-line documentation, and
60 * (2) changed temperature resolution to 0.1 degrees F.
63 * @subsection v200 V2.00
64 * 26 Oct 2002, Change include; (1) Micro Beacon II hardware changes including PIC18F252 processor,
66 * (3) GPS power control,
67 * (4) additional ADC input, and
68 * (5) LM60 temperature sensor.
71 * @subsection v101 V1.01
72 * 5 Dec 2001, Change include; (1) Changed startup message, and
73 * (2) applied SEPARATE pragma to several methods for memory usage.
76 * @subsection v100 V1.00
77 * 25 Sep 2001, Initial release. Flew ANSR-3 and ANSR-4.
83 * @section copyright_sec Copyright
85 * Copyright (c) 2001-2009 Michael Gray, KD7LMO
90 * @section gpl_sec GNU General Public License
92 * This program is free software; you can redistribute it and/or modify
93 * it under the terms of the GNU General Public License as published by
94 * the Free Software Foundation; either version 2 of the License, or
95 * (at your option) any later version.
97 * This program is distributed in the hope that it will be useful,
98 * but WITHOUT ANY WARRANTY; without even the implied warranty of
99 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
100 * GNU General Public License for more details.
102 * You should have received a copy of the GNU General Public License
103 * along with this program; if not, write to the Free Software
104 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
110 * @section design Design Details
112 * Provides design details on a variety of the components that make up the Pico Beacon.
118 * @page power Power Consumption
120 * Measured DC power consumption.
122 * 3VDC prime power current
127 * 18mA Processor running, all I/O off
131 * 120mA GPS running w/antenna
133 * 250mA DDS running and GPS w/antenna
135 * 420mA DDS running, GPS w/antenna, and PA chain on with no RF
148 // Public methods, constants, and data structures for each class.
150 static void timeInit(void);
152 static void tncInit(void);
153 static void tnc1200TimerTick(void);
158 * @defgroup sys System Library Functions
160 * Generic system functions similiar to the run-time C library.
166 * Calculate the CRC-16 CCITT of buffer that is length bytes long.
167 * The crc parameter allow the calculation on the CRC on multiple buffers.
169 * @param buffer Pointer to data buffer.
170 * @param length number of bytes in data buffer
171 * @param crc starting value
173 * @return CRC-16 of buffer[0 .. length]
175 static uint16_t sysCRC16(const uint8_t *buffer, uint8_t length, uint16_t crc)
177 uint8_t i, bit, value;
179 for (i = 0; i < length; ++i)
183 for (bit = 0; bit < 8; ++bit)
185 crc ^= (value & 0x01);
186 crc = ( crc & 0x01 ) ? ( crc >> 1 ) ^ 0x8408 : ( crc >> 1 );
197 * @defgroup rtc Real Time Interrupt tick
199 * Manage the built-in real time interrupt. The interrupt clock PRI is 104uS (9600 bps).
204 /// 16-bit NCO where the upper 8-bits are used to index into the frequency generation table.
205 static uint16_t timeNCO;
207 /// Audio tone NCO update step (phase).
208 static uint16_t timeNCOFreq;
211 * Initialize the real-time clock.
213 static void timeInit()
216 timeNCOFreq = 0x2000;
222 * @defgroup tnc TNC (Terminal Node Controller)
224 * Functions that provide a subset of the TNC functions.
229 /// The number of start flag bytes to send before the packet message. (360bits * 1200bps = 300mS)
230 #define TNC_TX_DELAY 45
232 /// The size of the TNC output buffer.
233 #define TNC_BUFFER_SIZE 40
235 /// States that define the current mode of the 1200 bps (A-FSK) state machine.
238 /// Stand by state ready to accept new message.
241 /// 0x7E bit stream pattern used to define start of APRS message.
244 /// Transmit the AX.25 header that contains the source/destination call signs, APRS path, and flags.
247 /// Transmit the message data.
250 /// Transmit the end flag sequence.
252 } TNC_TX_1200BPS_STATE;
254 /// AX.25 compliant packet header that contains destination, station call sign, and path.
255 /// 0x76 for SSID-11, 0x78 for SSID-12
256 static const uint8_t TNC_AX25_HEADER[] = {
257 'A' << 1, 'P' << 1, 'A' << 1, 'M' << 1, ' ' << 1, ' ' << 1, 0x60, \
258 'K' << 1, 'D' << 1, '7' << 1, 'S' << 1, 'Q' << 1, 'G' << 1, 0x78, \
259 'W' << 1, 'I' << 1, 'D' << 1, 'E' << 1, '2' << 1, ' ' << 1, 0x65, \
262 /// The next bit to transmit.
263 static uint8_t tncTxBit;
265 /// Current mode of the 1200 bps state machine.
266 static TNC_TX_1200BPS_STATE tncMode;
268 /// Counter for each bit (0 - 7) that we are going to transmit.
269 static uint8_t tncBitCount;
271 /// A shift register that holds the data byte as we bit shift it for transmit.
272 static uint8_t tncShift;
274 /// Index into the APRS header and data array for each byte as we transmit it.
275 static uint8_t tncIndex;
277 /// The number of bytes in the message portion of the AX.25 message.
278 static uint8_t tncLength;
280 /// A copy of the last 5 bits we've transmitted to determine if we need to bit stuff on the next bit.
281 static uint8_t tncBitStuff;
283 /// Buffer to hold the message portion of the AX.25 packet as we prepare it.
284 static uint8_t tncBuffer[TNC_BUFFER_SIZE];
287 * Initialize the TNC internal variables.
289 static void tncInit()
292 tncMode = TNC_TX_READY;
296 * Method that is called every 833uS to transmit the 1200bps A-FSK data stream.
297 * The provides the pre and postamble as well as the bit stuffed data stream.
299 static void tnc1200TimerTick()
301 // Set the A-FSK frequency.
302 if (tncTxBit == 0x00)
303 timeNCOFreq = 0x2000;
305 timeNCOFreq = 0x3aab;
310 // Generate a test signal alteranting between high and low tones.
311 tncTxBit = (tncTxBit == 0 ? 1 : 0);
315 // The variable tncShift contains the lastest data byte.
316 // NRZI enocde the data stream.
317 if ((tncShift & 0x01) == 0x00) {
324 // When the flag is done, determine if we need to send more or data.
325 if (++tncBitCount == 8)
330 // Once we transmit x mS of flags, send the data.
331 // txDelay bytes * 8 bits/byte * 833uS/bit = x mS
332 if (++tncIndex == TNC_TX_DELAY)
335 tncShift = TNC_AX25_HEADER[0];
337 tncMode = TNC_TX_HEADER;
340 tncShift = tncShift >> 1;
344 // Determine if we have sent 5 ones in a row, if we have send a zero.
345 if (tncBitStuff == 0x1f)
356 // The variable tncShift contains the lastest data byte.
357 // NRZI enocde the data stream.
358 if ((tncShift & 0x01) == 0x00) {
365 // Save the data stream so we can determine if bit stuffing is
366 // required on the next bit time.
367 tncBitStuff = ((tncBitStuff << 1) | (tncShift & 0x01)) & 0x1f;
369 // If all the bits were shifted, get the next byte.
370 if (++tncBitCount == 8)
374 // After the header is sent, then send the data.
375 if (++tncIndex == sizeof(TNC_AX25_HEADER))
378 tncShift = tncBuffer[0];
379 tncMode = TNC_TX_DATA;
381 tncShift = TNC_AX25_HEADER[tncIndex];
384 tncShift = tncShift >> 1;
389 // Determine if we have sent 5 ones in a row, if we have send a zero.
390 if (tncBitStuff == 0x1f)
401 // The variable tncShift contains the lastest data byte.
402 // NRZI enocde the data stream.
403 if ((tncShift & 0x01) == 0x00) {
410 // Save the data stream so we can determine if bit stuffing is
411 // required on the next bit time.
412 tncBitStuff = ((tncBitStuff << 1) | (tncShift & 0x01)) & 0x1f;
414 // If all the bits were shifted, get the next byte.
415 if (++tncBitCount == 8)
419 // If everything was sent, transmit closing flags.
420 if (++tncIndex == tncLength)
424 tncMode = TNC_TX_END;
426 tncShift = tncBuffer[tncIndex];
429 tncShift = tncShift >> 1;
434 // The variable tncShift contains the lastest data byte.
435 // NRZI enocde the data stream.
436 if ((tncShift & 0x01) == 0x00) {
443 // If all the bits were shifted, get the next one.
444 if (++tncBitCount == 8)
449 // Transmit two closing flags.
452 tncMode = TNC_TX_READY;
457 tncShift = tncShift >> 1;
464 * Generate the plain text position packet.
466 static int tncPositionPacket(void)
468 int32_t latitude = ao_gps_data.latitude;
469 int32_t longitude = ao_gps_data.longitude;
470 int32_t altitude = ao_gps_data.altitude;
479 char lat_sign = 'N', lon_sign = 'E';
483 latitude = -latitude;
488 longitude = -longitude;
491 lat_deg = latitude / 10000000;
492 latitude -= lat_deg * 10000000;
494 lat_min = latitude / 10000000;
495 latitude -= lat_min * 10000000;
496 lat_frac = (latitude + 50000) / 100000;
498 lon_deg = longitude / 10000000;
499 longitude -= lon_deg * 10000000;
501 lon_min = longitude / 10000000;
502 longitude -= lon_min * 10000000;
503 lon_frac = (longitude + 50000) / 100000;
508 altitude = altitude * (int32_t) 1000 / (int32_t) 3048;
510 return sprintf ((char *) tncBuffer, "=%02u%02u.%02u%c\\%03u%02u.%02u%cO /A=%06u\015",
511 lat_deg, lat_min, lat_frac, lat_sign,
512 lon_deg, lon_min, lon_frac, lon_sign,
517 tncFill(uint8_t *buf, int16_t len)
523 while (tncMode != TNC_TX_READY && l < len) {
525 for (bit = 0; bit < 8; bit++) {
526 b = b << 1 | (timeNCO >> 15);
527 timeNCO += timeNCOFreq;
533 if (tncMode == TNC_TX_READY)
539 * Prepare an AX.25 data packet. Each time this method is called, it automatically
540 * rotates through 1 of 3 messages.
542 * @param dataMode enumerated type that specifies 1200bps A-FSK or 9600bps FSK
544 void ao_aprs_send(void)
551 tncLength = tncPositionPacket();
553 // Calculate the CRC for the header and message.
554 crc = sysCRC16(TNC_AX25_HEADER, sizeof(TNC_AX25_HEADER), 0xffff);
555 crc = sysCRC16(tncBuffer, tncLength, crc ^ 0xffff);
557 // Save the CRC in the message.
558 tncBuffer[tncLength++] = crc & 0xff;
559 tncBuffer[tncLength++] = (crc >> 8) & 0xff;
561 // Prepare the variables that are used in the real-time clock interrupt.
566 tncMode = TNC_TX_SYNC;
568 ao_radio_send_lots(tncFill);