The UDS client API provides functionality for sending diagnostic requests to UDS servers.

Basic Usage

Initialization

UDSClient_t client;
UDSTp_t *transport = /* initialize your transport */;
 
UDSClientInit(&client);
client.tp = transport;

For transport initialization, see Transport Selection.

Sending Requests

// Send Diagnostic Session Control
UDSSendDiagSessCtrl(&client, UDS_LEV_DS_EXTDS);
 
// Send Read Data By Identifier
uint16_t dids[] = {0xF190};
UDSSendRDBI(&client, dids, 1);
 
// Send ECU Reset
UDSSendECUReset(&client, UDS_LEV_RT_HR);

Processing Responses

while (client.state != UDS_CLIENT_IDLE) {
    UDSClientPoll(&client);
    // Handle events in callback
}

Client Structure

The UDSClient structure contains:

Timeouts: p2_ms, p2_star_ms - Server response timing parameters
Transport: tp - Pointer to ISO-TP transport layer
State: state - Current client state
Options: options, defaultOptions - Request behavior flags
Callback: fn, fn_data - Event handler and user data
Buffers: recv_buf, send_buf - Internal message buffers

Request Options

Combine these flags when sending requests:

Flag	Description
`UDS_SUPPRESS_POS_RESP`	Suppress positive response (0x80 bit)
`UDS_FUNCTIONAL`	Send as functional request (broadcast)
`UDS_IGNORE_SRV_TIMINGS`	Ignore the server-provided P2/P2* values returned by a successful call to DiagnosticSessionControl

Example:

client.options = UDS_SUPPRESS_POS_RESP | UDS_FUNCTIONAL;
UDSSendTesterPresent(&client);
// client.options is cleared automatically after each request

Event-Driven API

The client uses callbacks to notify the application of events:

int fn(UDSClient_t *client, UDSEvent_t evt, void *ev_data) {
    switch (evt) {
        case UDS_EVT_SendComplete:
            // Request sent successfully
            break;
        case UDS_EVT_ResponseReceived:
            // Response received
            break;
        case UDS_EVT_Err:
            // Error occurred
            UDSErr_t *err = (UDSErr_t *)ev_data;
            printf("Error: %s\n", UDSErrToStr(*err));
            break;
    }
    return 0;
}
 
client.fn = client_callback;

Supported Services

See UDS Services.

Unpacking Responses

Helper functions are provided to parse complex responses:

// Security Access response
struct SecurityAccessResponse resp;
UDSUnpackSecurityAccessResponse(&client, &resp);
 
// Request Download response
struct RequestDownloadResponse dl_resp;
UDSUnpackRequestDownloadResponse(&client, &dl_resp);
 
// Routine Control response
struct RoutineControlResponse rc_resp;
UDSUnpackRoutineControlResponse(&client, &rc_resp);
 
// Read Data By Identifier response
UDSRDBIVar_t vars[] = {
    {.did = 0xF190, .data = buffer, .len = sizeof(buffer)}
};
UDSUnpackRDBIResponse(&client, vars, 1);

Configuration

Client behavior can be configured at compile-time:

Define	Default	Description
`UDS_CLIENT_DEFAULT_P2_MS`	150	Default P2 timeout (ms)
`UDS_CLIENT_DEFAULT_P2_STAR_MS`	1500	Default P2* timeout (ms)
`UDS_CLIENT_SEND_BUF_SIZE`	4095	Send buffer size
`UDS_CLIENT_RECV_BUF_SIZE`	4095	Receive buffer size