diff options
Diffstat (limited to 'src/class')
| -rw-r--r-- | src/class/cdc/cdc_device.c | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/src/class/cdc/cdc_device.c b/src/class/cdc/cdc_device.c index 6c1bf6bb2..e39adc5fa 100644 --- a/src/class/cdc/cdc_device.c +++ b/src/class/cdc/cdc_device.c @@ -75,14 +75,27 @@ CFG_TUSB_MEM_SECTION static cdcd_interface_t _cdcd_itf[CFG_TUD_CDC]; static void _prep_out_transaction (cdcd_interface_t* p_cdc) { + uint8_t const rhport = TUD_OPT_RHPORT; + uint16_t available = tu_fifo_remaining(&p_cdc->rx_ff); + // Prepare for incoming data but only allow what we can store in the ring buffer. - uint16_t const available = tu_fifo_remaining(&p_cdc->rx_ff); - TU_VERIFY( available >= sizeof(p_cdc->epout_buf), ); + // TODO Actually we can still carry out the transfer, keeping count of received bytes + // and slowly move it to the FIFO when read(). + // This pre-check reduces endpoint claiming + TU_VERIFY(available >= sizeof(p_cdc->epout_buf), ); + + // claim endpoint + TU_VERIFY(usbd_edpt_claim(rhport, p_cdc->ep_out), ); - // claim endpoint and submit transfer - if ( usbd_edpt_claim(TUD_OPT_RHPORT, p_cdc->ep_out) ) + // fifo can be changed before endpoint is claimed + available = tu_fifo_remaining(&p_cdc->rx_ff); + + if ( available >= sizeof(p_cdc->epout_buf) ) { + usbd_edpt_xfer(rhport, p_cdc->ep_out, p_cdc->epout_buf, sizeof(p_cdc->epout_buf)); + }else { - usbd_edpt_xfer(TUD_OPT_RHPORT, p_cdc->ep_out, p_cdc->epout_buf, sizeof(p_cdc->epout_buf)); + // Release endpoint since we don't make any transfer + usbd_edpt_release(rhport, p_cdc->ep_out); } } |