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UDS Client {#client}

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 \ref transport_layers.

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 \ref 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 \ref services "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_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

See Also

  • \ref server.h "Server API"
  • \ref tp.h "Transport Layer API"
  • \ref examples/linux_rdbi_wdbi/client.c "RDBI/WDBI Client Example"
  • \ref examples/linux_server_0x27/client.c "Security Access Client Example"