diff --git a/src/class/usbtmc/usbtmc_device.c b/src/class/usbtmc/usbtmc_device.c index 07190d89f..e248341ac 100644 --- a/src/class/usbtmc/usbtmc_device.c +++ b/src/class/usbtmc/usbtmc_device.c @@ -497,9 +497,21 @@ bool usbtmcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint #if (CFG_TUD_USBTMC_ENABLE_488) case USBTMC_MSGID_USB488_TRIGGER: - // Spec says we halt the EP if we didn't declare we support it. - TU_VERIFY(usbtmc_state.capabilities->bmIntfcCapabilities488.supportsTrigger); - TU_VERIFY(tud_usbtmc_msg_trigger_cb(msg)); + // Unlike the messages above, TRIGGER is complete on arrival and has no response, so nothing else + // will move us out of STATE_IDLE. Do it here, otherwise the tud_usbtmc_start_bus_read() below (and + // any call the application makes from its callback) is a no-op and the bulk-OUT endpoint is left + // un-armed, silently timing out every subsequent host transfer. + TU_VERIFY(atomicChangeState(STATE_IDLE, STATE_NAK)); + + // Spec says we halt the EP if we didn't declare we support it; do the same when the application + // rejects the trigger. The callback result must not be wrapped in TU_VERIFY() here: returning + // early would skip both the stall and the re-arm below. + if (!usbtmc_state.capabilities->bmIntfcCapabilities488.supportsTrigger || + !tud_usbtmc_msg_trigger_cb(msg)) { + usbd_edpt_stall(rhport, usbtmc_state.ep_bulk_out); + return false; + } + tud_usbtmc_start_bus_read(); break; #endif diff --git a/src/class/usbtmc/usbtmc_device.h b/src/class/usbtmc/usbtmc_device.h index 3dc700876..efda84f16 100644 --- a/src/class/usbtmc/usbtmc_device.h +++ b/src/class/usbtmc/usbtmc_device.h @@ -25,7 +25,6 @@ // * tud_usbtmc_open_cb // * tud_usbtmc_msg_data_cb // * tud_usbtmc_msgBulkIn_complete_cb -// * tud_usbtmc_msg_trigger_cb // * (successful) tud_usbtmc_check_abort_bulk_out_cb // * (successful) tud_usbtmc_check_abort_bulk_in_cb // * (successful) tud_usmtmc_bulkOut_clearFeature_cb