diff options
Diffstat (limited to 'README.mkd')
| -rw-r--r-- | README.mkd | 66 |
1 files changed, 66 insertions, 0 deletions
@@ -1,8 +1,74 @@ OBD-II Support Library in C ============================= +TODO isotp needs to accept responses on an ID other that the request's arb id - +or maybe we have 2 isotp instances, for rx and tx. + +* Response's arb id is assigned ID plus 0x8 +* Functional daignostic request (Broadcast), 0x7df arb id +* Standard ECU requests to 0x7e0 - 0x7e7 + +* Some requests don't need PIDs - e.g. mode 3 + * some responses don't have PIDs, just payload - e.g. mode 3 + +* Service ID + 0x40 == positive response +* Response includes PID echo - use this to match up request/response +* Response ID, ISO-TP PCI, ISO-TP length, service response ID, PID echo, data + +I send the request and give a callback +when the response arrives for the matchin service and PID - on any arb id, since +this may be a broadcast - call my callback. + + +TODO do you want to provide the callback to the Handler, or to each +individual send?o +ok, what are the use cases here. + +you're going to request a few PIDs over and over again at some frequency +you're going to request DTCs once and read the response +you're going to clear DTCs once + +i'd rather use the same diagnostic handler to send all of the differet messages +rather than create one for each use. that way ai can + +but that does complicate the memory management because it'll need to create +some internal data structures. + +at the simplest, what does this handler have to do? + +* store the request arb id, mode, pid, and payload locally +* send a can message +* get all new can messages passed to it +* Check the incoming can message to see if it matches one of the standard ECU + response IDs, or our arb ID + 0x8 +* if it matches, parse the diagnostic response and call the callback + +that seems pretty simple and not worth greatly increasing the internal state to +handle multiple requests + +what we need is another layer on top of that to handle the repeated requests. + ## API + void my_callback(const DiagnosticResponse* response) { + } + + DiagnosticRequestHandler handler = diagnostic_init(my_callback); + DiagnosticRequest request = { + arbitratin_id: 0x7df, + mode: OBD2_MODE_POWERTRAIN_DIAGNOSTIC_REQUEST, + pid: 3 + }; + + diagnostic_send(&handler, &request); + while(true) { + diagnostic_handle_can_frame(&handler, 42, data, 8); + } + + diagnostic_request_pid(&handler, DIAGNOSTIC_STANDARD_PID, 42 + + diagnostic_destroy(&handler); + ## Testing The library includes a test suite that uses the `check` C unit test library. |