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projects:pic32mx_obd_evaluation_board [2017/01/11 16:49] admin [Commands] |
projects:pic32mx_obd_evaluation_board [2019/08/20 18:33] admin [PIC32MX OBD Evaluation Board] |
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| ====== PIC32MX OBD Evaluation Board ====== | ====== PIC32MX OBD Evaluation Board ====== | ||
| - | {{:projects:dsc_5593_800x536.jpg?512 |}} | + | {{:projects:dsc_5593_800x536.jpg?356 |}} |
| ===== Requirements ===== | ===== Requirements ===== | ||
| ===== Basics of communication protocol ===== | ===== Basics of communication protocol ===== | ||
| Line 92: | Line 92: | ||
| * low level communication with devices on I²C bus | * low level communication with devices on I²C bus | ||
| ==== Commands ==== | ==== Commands ==== | ||
| + | ^ c | calculate CRC checksum for given data | | ||
| ^ C | configure communication parameters | | ^ C | configure communication parameters | | ||
| ^ d | get date and time | | ^ d | get date and time | | ||
| Line 100: | Line 101: | ||
| ^ i | read data from I²C device | | ^ i | read data from I²C device | | ||
| ^ I | write data to 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 ==== | ==== Configuring communication parameters ==== | ||
| <code> | <code> | ||
