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Diffstat (limited to 'README.mkd')
| -rw-r--r-- | README.mkd | 58 |
1 files changed, 44 insertions, 14 deletions
@@ -1,32 +1,63 @@ ISO-TP (ISO 15765-2) Support Library in C ================================ -## API +This is a platform agnostic C library that implements the ISO 15765-2 (also +known as ISO-TP) protocol, which runs over a CAN bus. Quoting Wikipedia: -First, set up some shim functions to your lower level system: +>ISO 15765-2, or ISO-TP, is an international standard for sending data packets +>over a CAN-Bus. The protocol allows for the transport of messages that exceed +>the eight byte maximum payload of CAN frames. ISO-TP segments longer messages +>into multiple frames, adding metadata that allows the interpretation of +>individual frames and reassembly into a complete message packet by the +>recipient. It can carry up to 4095 bytes of payload per message packet. - void debug(const char* format, ...) { - ... - } +This library doesn't assume anything about the source of the ISO-TP messages or +the underlying interface to CAN. It uses dependency injection to give you +complete control. + +The current version supports *only single frame ISO-TP messages*. This is fine +for OBD-II diagnostic messages, for example, but this library needs some +additional work before it can support sending larger messages. + +## Usage +First, create some shim functions to let this library use your lower level +system: + + // required, this must send a single CAN message with the given arbitration + // ID (i.e. the CAN message ID) and data. The size will never be more than 8 + // bytes. void send_can(const uint16_t arbitration_id, const uint8_t* data, const uint8_t size) { ... } + // optional, provide to receive debugging log messages + void debug(const char* format, ...) { + ... + } + + + // not used in the current version void set_timer(uint16_t time_ms, void (*callback)) { ... } -Then, set up a callback and send an ISO-TP message: +With your shims in place, create an IsoTpShim object to pass them around: + + IsoTpShim shims = isotp_init_shims(debug, send_can, set_timer); + +### API + +With your shims in hand, send an ISO-TP message: - // this is your callback for when the message is completely sent - it's - // optional + // Optiona: This is your callback that will be called when the message is + // completely sent. If it was single frame (the only type supported right + // now), this will be called immediately. void message_sent(const IsoTpMessage* message, const bool success) { // You received the message! Do something with it. } - IsoTpShim shims = isotp_init_shims(debug, send_can, set_timer); IsoTpHandle handle = isotp_send(&shims, 0x100, NULL, 0, message_sent); if(handle.completed) { @@ -57,9 +88,10 @@ Then, set up a callback and send an ISO-TP message: Finally, receive an ISO-TP message: - // This is your callback for when a complete ISO-TP message is received at - // the arbitration ID you specify - it's optional. The completed message is - // also returned by isotp_receive_can_frame + // Optional: This is your callback for when a complete ISO-TP message is + // received at the arbitration ID you specify. The completed message is + // also returned by isotp_receive_can_frame, which can sometimes be more + // useful since you have more context. void message_received(const IsoTpMessage* message) { } @@ -84,8 +116,6 @@ Finally, receive an ISO-TP message: } } -// TODO add an optional dispatcher to handle multiple open requests - ## Testing The library includes a test suite that uses the `check` C unit test library. |