1 PROTOCOL BETWEEN HOST AND MASTER PIC
2 ====================================
4 9600 8N1 over the serial port. The PIC must obey the host's flow
5 control line, so that if the host gets backed up none of the PICs
6 messages can get lost. (If this is too hard, then the PIC should
7 attempt to buffer some data while the host is busy but if the PIC's
8 buffer gets too full it should panic.)
10 Each message consists of a number of 8-bit bytes. The top bit of each
11 byte is 1 iff there is another byte in the message.
13 First Second ASCII Message Brief
14 Byte byte etc. or hex name description
18 > 1 0100 TTT 0 TTTTTTT (a0) POINT Point T fire
19 > 1 1111 111 .... (ff) NMRADATA NMRA data
20 > 1 0001 XXX 0 XXXXXXX (88+) PING Ping `X' (please Pong `X')
21 > 1 0010 RRR E RRR... (90+) POLARITY Set polarity
22 > 1 0011 000 0 MMMMMMM (98+) WATCHDOG W'dog reset, t/o <M*16>ms from now
23 > 0 0010 001 (11) ON Power on
24 > 0 0010 000 (10) OFF Power off
26 ;> 00000000 CRASHED Acknowledge panic, go to readout mode
27 ;> 00001002 (0a) TELLMODE Confirm mode - say HELLO or CRASHED
28 ; if crashed, undoes the effect of ack
30 ; In crash readout mode:
32 ; 00000000 MS Select crash readout mode if not already
33 ; Reset crash readout pointer to 0
35 ; 00001000 Acknowledge RS232 framing error or overrun
38 ; 1vvvvvvv M Prepare byte 0vvvvvvv for transmission to the slave
40 ; 00000nnn M (n>0) prepare to receive nnnn bytes from slave
41 ; 0001nnnn M (n>0) transmit nnnn bytes of our own from the
44 ; 001sssss M Select slave S^0x10. Then:
46 ; Transmit just 0vvvvvvv to slave
47 ; and then send some some unspecified byte to host
49 ; Receive nnnn bytes, forwarding each one
51 ; After the transaction is complete, 1vvvvvvv
52 ; or 0000nnnn must be specified again before
53 ; 001sssss is repeated.
55 ; 01bbbbbb MS Supply 6 bits for crash readout pointer
56 ; (crash readout mode only)
57 ; Effect is FSR << 6; FSR |= bbbbbb
61 < 1 001Y SSS 0 SSSSSSS (9?) DETECT Train is (Y=1) or is not (Y=0) at S
62 < 1 0001 XXX 0 XXXXXXX (88+) PONG Pong `X' (reply to Ping `X')
63 < 0 000 1001 (HT) HELLO I am booted
64 < 0 000 1011 (VT) AAARGH Followed by debug chars (only)
65 < 0 000 1101 (CR) WTIMEOUT Watchdog timeout happened
66 < 0 000 0111 (BEL) FAULT Fault exists
67 < 0 000 0110 (ACK) FIXED Fault now fixed
68 < 0 0100 PPP (20+) POINTED Point change done using capacitor P
69 < 0 0101 PPP (28+) CHARGED Point capacitor P is now charged
70 < 0 00000 FF NMRADONE Have processed F NMRADATA message(s)
72 < 0000 1010 (LF) } debugging output 0x0a (newline) and
73 < 001C CCCC } (works with terminal 0x20-0x7e
74 < 01CC CCCC except 0111 1111 } emulator, or host logs) (printing ASCII)
76 (These are all shown big-endian, and all of the numerical
77 representations are big-endian too. Where a number is split across
78 two or more bytes, the relevant bits are to be concatenated, in the
79 order shown, ie bits from the MS byte first, into a larger number.)
82 HELLO, AAARGH and debugging output
83 ----------------------------------
85 When the master PIC starts up and has confirmed that all is well (all
86 of the other PICs are there, etc), it should send HELLO once.
88 If the host makes a mistake (eg, sends an unknown command, or does
89 something else wrong) or something goes horribly wrong, the master PIC
92 The PIC may always send printing ASCII characters and spaces and
93 newlines (ie, bytes 0x0a, 0x20-0x7e). These will print out nicely in
94 a terminal emulator, if that's what's running on the host. If the
95 host is running the real software, that software will put the
96 characters sent in its log or somewhere else nicely accessible.
98 Apart from debugging output, the PIC should send nothing before HELLO
99 and nothing after AAARGH.
105 The host can send ON and OFF to turn the track (and various other
106 stuff) on and off. After ON, the track power should be enabled and
107 transmitting NMRA idle, and the CDU should be enabled.
109 If the power is ON, and a track power short circuit is detected, the
110 PIC should send FAULT. When the short circuit is removed, the PIC
111 should send FIXED but not fully reenable track power; track power
112 should be reenabled when the host transmits ON.
115 Track and CDU Track and CDU
116 disabled -------ON-------> enabled
119 | |Short circuit detected
123 \__________________ V
125 fixes the short Short circuit
126 (User Fault indicator lit)
133 The ON command should cause the CDU to be enabled (and of course all
134 point motor outputs should be disabled first - see README.circuitry).
136 Following ON the host must wait until it receives CHARGED before
137 attempting to change a point. After CHARGED it may send POINT, to
138 activate the point and direction specified by T. The PICs will report
139 POINTED when the point has stopped moving, and CHARGED when the CDU is
140 ready to change another point (the host may not send POINT for a point
141 on the same CDU until then).
143 Currently there is only one CDU so P is always 0 (but the PICs need
144 not check that the received P value is 0; they may simply assume it).
147 ----ON-----> CDU is ------CHARGED---> CDU is charged
148 charging _. and ready
155 is recharging <----POINTED---- Point is changing
162 The host may send PING at any time; the PIC should reply with PONG
163 with the same X as was in the PING message. The host may not send
164 another PING until the first one's PONG has come back.
167 POLARITY and POLARISED
168 ----------------------
170 The POLARITY command may be sent whether the track power is enabled or
171 disabled. The polarity of each segment is `unreversed' after ON; it
172 remains constant until from then on except as modified by POLARITY.
174 The command is of variable length (but at least two bytes):
176 > 1 0010 RRR E RRR... POLARITY Set polarity
178 Each byte after the first contains 7 more R bits. The first R bit
179 (most significant R bit in the first byte) corresponds to track
180 reversal segment 1; The next bit (2nd most significant bit in the
181 first byte) corresponds to track reversal segment 2; and so on.
183 Bits which do not correspond to defined reversal segments will be
184 ignored by the PICs. The host must send exactly as many bytes as are
185 necessary to include all of the reversal segments for each reversers
186 board (for every potential reversal segment, regardless of whether
187 that segment is a defined segment corresponding to some actual track;
188 however a board with _no_ reversers segments used does not count).
190 For example, if there are 14 reversible segments (numbered 1 to 14)
191 then the following message
192 1 0010 000 1 000 1000 0 111 1010 Actual message
193 (E RRR) (E RRR RRRR) (E RRR R---) } helpful annotations
194 1 111 1111 } and commentary
195 123 456 7890 123 4567 }
196 specifies to reverse segments 7 and 11 to 14. The trailing bits are
197 for segments 15 to 17 and are ignored. (Note that the assignment of
198 physical segments to segment numbers is complex due to bit-twiddling.
199 see detpic/reverse.asm and layout/data2safety.)
201 The PIC will reply to POLARITY with POLARISED when the polarity change
202 is complete. The host must not send another POLARITY until then.
205 NMRADATA and NMRAFULL
206 ---------------------
208 The data bits in all of the bytes of the NMRADATA command (including
209 the first) are simply transmitted as NMRA data to the track (most
210 significant bit first). The top `end of packet' bit is not
213 The first 14 data bits in the NMRA packet should be 1s. (i.e. the
214 first two complete bytes should be 11111111 11111111). Packets
215 beginning with a different first byte are reserved for other commands
216 to the PIC and the 14 idle bits are a requirement of the NMRA
219 The maximum NMRA message length is 15 bytes each carrying 7 bits of
220 actual NMRA data (i.e. 105 bits).
222 Up to three NMRADATA commands may be supplied by the host to the
223 master PIC, and their will be transmitted in sequence. After each
224 NMRADATA is completed, the PIC will send an NMRAFULL message to the
225 host. In the NMRAFULL message, F is the number of completely-received
226 NMRADATA commands awaiting transmission to the track.
228 If the PIC runs out of NMRA data, it will transmit an NMRA idle
229 stream. It is an error for the host to try to have more than three
230 outstanding NMRADATA commands.
236 The DETECT command indicates to the host whether there is currently a
237 train being detected at a specific location. The PIC must send a
238 DETECT with Y=1 when a train is detected in a location where there was
239 previously none, and with Y=0 when a train ceases to be detectable for
240 more than a small amount of time.
242 At HELLO, the host will assume that no trains are being detected.
245 RAM (data) memory map
246 =====================
248 The data memory map (for PIC18F458) looks like this:
250 0x000-0x05f Access bank RAM - RAM locations accessible via
251 access bank instructions; also form part of
253 0x060-0x0ff Remainder of RAM page 0, accessible only via correct
254 BSR setting (ie, BSR==0), INDF, etc.
256 0x100-0x1ff RAM page 1, accessible only via bank switching etc.
257 0x200-0x2ff RAM page 2, accessible only via bank switching etc.
258 0x300-0x3ff RAM page 3, accessible only via bank switching etc.
259 0x400-0x4ff RAM page 4, accessible only via bank switching etc.
260 0x500-0x5ff RAM page 5, accessible only via bank switching etc.
262 0x600-0xeff Nothing here, don't try to access.
264 0xf00-0xf5f SFR's (memory-mapped peripherals etc.) accessible
265 only via correct BSR, INDF, etc - but these are only
266 the CAN SFR's and we do not use the CAN controller.
267 0xf60-0xfff SFR's accessible via access bank (also form part
271 See common.inc for actual uses of the RAM areas.
274 Program (flash etc.) memory map
275 ===============================
277 Program memory map (for PIC18F458) looks like this:
279 0x00 0000- Program memory
280 0x00 7fff Contains actual program instructions and can also
281 contain preprogrammed data provided via special .asm
282 files. Notable contents and addresses:
283 0x00 0000 reset vector
284 0x00 0008 high-priority interrupt vector
285 0x00 0018 low-priority interrupt vector
286 See common.inc for some special tables in here, for
287 morse messages, pin/hardware-object definitions, etc.
289 0x20 0000- ID locations
290 0x20 0007 Programming which varies per PIC. Programmed by
291 idlocs*.asm which are made by make-idlocs and
292 included in perpic*.hex. Contents:
296 bits 4-0 = PIC number (guaranteed to be
297 in the range 0..31 inclusive)
299 bit 7 = 1 for the main PIC (#0)
301 bit 6 = 1 for Reversers board, 0 for Detectors
302 bits 0-5 = currently unused, set to 0
304 0x20 0002- } not currently used,
305 0x20 0007 } may contain anything
307 0x30 0000- Hardware configuration
308 0x30 000f Defines (clock source, WDT operation, etc.)
309 Probably best not to touch. `config.asm' provides
310 correct contents, which is included in *-withcfg.hex
313 0x3f fffe- Hardware device ID
314 0x3f ffff Fixed at manufacturing time; can be read to discover
315 hardware type and version (probably not very useful)
317 0xf0 0000- EEPROM data area
318 0xf0 00ff Not currently used by us
320 0x01 0000- } These locations, not listed above,
321 0x1f ffff } do not correspond to anything - there
322 0x20 0008- } is no hardware or memory in the chip
323 0x2f ffff } at these locations.
325 0x3f fffd } Accessing them isn't useful
326 0x40 0000- } and should probably be avoided.
330 (Buffer page 50 0000h reserved for NMRA) XXXX these look wrong
331 (Buffer page 40 0000h reserved for i2c) XXXX -iwj
337 (slave addresses will be 10xxxxx where xxxxx=PIC number above)