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--- projects:pic32mx_obd_evaluation_board [2017/01/11 16:49] – [Commands] admin
+++ projects:pic32mx_obd_evaluation_board [2026/10/25 19:30] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== PIC32MX OBD Evaluation Board ======
-{{:projects:dsc_5593_800x536.jpg?512 |}}
+{{:projects:dsc_5593_800x536.jpg?456 |}}
 ===== Requirements =====
 ===== Basics of communication protocol =====
@@ Line 92: / 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 100: / 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>