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--- projects:pic32mx_obd_evaluation_board [2017/01/06 15:31]
admin [μSD card]
+++ projects:pic32mx_obd_evaluation_board [2019/08/20 18:33]
admin [PIC32MX OBD Evaluation Board]
@@ Line 1: / Line 1: @@
 ====== PIC32MX OBD Evaluation Board ======
-{{:projects:dsc_5593_800x536.jpg?512 |}}
+{{:projects:dsc_5593_800x536.jpg?356 |}}
 ===== Requirements =====
 ===== Basics of communication protocol =====
@@ Line 73: / Line 73: @@
 ^ R | RFID module |
 ^ Q | data acquisition module |
-^ S | μSD card |
 ==== Generic NAK responses (shared by all modules) ====
@@ Line 93: / Line 92: @@
   * low level communication with devices on I²C bus
 ==== Commands ====
+^ c | calculate CRC checksum for given data |
 ^ C | configure communication parameters |
 ^ d | get date and time |
@@ Line 101: / Line 101: @@
 ^ i | read data from I²C device |
 ^ I | write data to I²C device |
+==== Calculating CRC checksum ====
+<code>
+Query
+----------------------------------------------
+| SOF | P | c | TYPE | P1..P4 | D1..DN | EOF |
+----------------------------------------------
+</code>
+where
+^ TYPE | 1b | s - 16-bit CRC-CCITT calculated by software (only P4 used); d - CRC calculated by DMA module |
+^ P1 | 1b | 0 - input data not reflected (MSB first); ≠0 - input data reflected (LSB first) |
+^ P2 | 1b | length of CRC polynom (1..32) |
+^ P3 | 4b | CRC polynom |
+^ P4 | 4b | CRC seed |
+^ D1..DN | Nb | data in form of ASCII HEX |
+<code>
+Response
+-------------------------------------------
+| SOF | P | 00 | CRC | TIME | CHSUM | EOF |
+-------------------------------------------
+</code>
+where
+^ CRC | 4b | calculated CRC |
+^ TIME | 2b | time in μs the calculation process took |
+Error codes
+^ N02 | Invalid parameters provided |
 ==== Configuring communication parameters ====
 <code>
@@ Line 253: / Line 278: @@
 Error codes
 ^ ?? | ?? |
-===== μSD card =====
-μSD card module provides API for
-  * determining last sector written by Carmon log
-  * reading sector from the device
-==== Commands ====
-^ l | get number of last sector written by Carmon logger |
-^ r | reads one sector from the card |
 ===== Carmon logger =====
 Carmon logger module provides API for
   * configuring operating mode of Carmon logger device
+  * determining last sector written by Carmon logger
+  * reading sectors from the log device
 ==== Commands ====
 ^ C | configure the module |
+^ l | get number of last sector written by Carmon logger |
+^ R | read blocks from the log device according to provided parameters |
+^ r | read subsequent blocks from the log device according to parameters previously set via 'R' command|
 ==== Configure the module ====
 <code>
@@ Line 281: / Line 303: @@
 | SOF | L | A | CHSUM | EOF |
 -----------------------------
+</code>
+==== Read sectors from the log device according to provided parameters ====
+<code>
+Query
+--------------------------------------------------------
+| SOF | L | R | CONF | SECSTART | BLKNUM | CHSUM | EOF |
+--------------------------------------------------------
 </code>
+where
+^ CONF | 1b | configures how sectors are transfered to the master |
+^ SECSTART | 4b | number of 1st sector to be read |
+^ BLKNUM | 4b | number of blocks to be read |
+Format of CONF word:
+^ bit# ^7^6^5^4^3^2..0^
+^ | NA | NA | NA | 1/0..binary/ASCII mode | 1/0..block is/is not compressed | number of sectors in block (1-8) |
+<code>
+ACK response - standard ASCII mode
+-----------------------------------------------
+| SOF | L | A | SN | B1D1..B1DN | CHSUM | EOF |
+-----------------------------------------------
+-----------------------------------------------
+| SOF | L | A | SN | B2D1..B2DN | CHSUM | EOF |
+-----------------------------------------------
+...
+-----------------------------------------------
+| SOF | L | A | SN | BMD1..BMDN | CHSUM | EOF |
+-----------------------------------------------
+ACK response - binary mode
+---------------------------------------------------
+| DLE | STX | SN | B1D1..B1DN | CHSUM | DLE | ETX |
+---------------------------------------------------
+---------------------------------------------------
+| DLE | STX | SN | B2D1..B2DN | CHSUM | DLE | ETX |
+---------------------------------------------------
+...
+---------------------------------------------------
+| DLE | STX | SN | BMD1..BMDN | CHSUM | DLE | ETX |
+---------------------------------------------------
+</code>
+where
+^ SN | 1b | sequence number (01-FF); incremented with each packet; useful for detection of packet loss |
+^ BxD1..BxDN | Nb | Xth data block (CONF[2..0] sectors) |
+note: When operating in binary mode, each DLE data byte is replaced with sequence of two DLE bytes.
 ===== RFID module =====
 RFID module provides API for