Dear Nordic Support team,
Currently I am in the process of adding the USBD_CDC_ACM driver code to our existing application following your usbd_ble_uart example. I can receive messages okay if they are less than 64 bytes long but when a message is greater than 64 bytes then the next message received has the first byte missing. I am using SDK 15.2 and running a SES project.
This is the message I am sending with a line feed at the end.
{"mac":"68B9D3D0BEC0","idonly":0,"duration":10,"fctrl":1,"cloud":1,"utc":1606456028,"type":"MQTT","fsrvid":"0%0","msg":"shake","rssi":-40,"scanenable":0}
Here is the RX event code
case APP_USBD_CDC_ACM_USER_EVT_RX_DONE:
{
ret_code_t ret;
NRF_LOG_INFO("Bytes waiting: %d, Index %d", app_usbd_cdc_acm_bytes_stored(p_cdc_acm), rxIndex);
do
{
/*Get amount of data transfered*/
size_t size = app_usbd_cdc_acm_rx_size(p_cdc_acm);
// NRF_LOG_INFO("RX: size: %lu char: %c", size, m_rx_buffer[0]);
//NRF_LOG_INFO("RX: %c", m_rx_buffer[0]);
/* Fetch data until internal buffer is empty */
if(firstRx) /* Breakpoint B */
{
ret = app_usbd_cdc_acm_read(&m_app_cdc_acm,
&m_rx_buffer[++rxIndex],
1);
//NRF_LOG_INFO("P2 %d", rxIndex);
}
else
{
ret = app_usbd_cdc_acm_read(&m_app_cdc_acm,
&m_rx_buffer[rxIndex++],
1);
//NRF_LOG_INFO("P3 %d",rxIndex );
}
//nrf_delay_ms(1);
} while (ret == NRF_SUCCESS);
if(m_rx_buffer[rxIndex-1] == '\n')
{
NRF_LOG_INFO("Rx %s",m_rx_buffer); /* breakpoint A */
NRF_LOG_INFO("P1");
rxIndex =0;
firstRx = false;
memset(m_rx_buffer, 0x00, sizeof(m_rx_buffer));
}
//bsp_board_led_invert(LED_CDC_ACM_RX);
break;
}
To reproduce this problem I first place a breakpoint at position A
I then ran the application and sent the message via a serial terminal with a Line Feed at the end.
It hits breakpoint A and the contents is as shown below with the complete message.
image 1
I then activate breakpoint B and click play.
I then resend the message changing it slightly i.e.
{"maw":"68B9D3D0BEC0","idonly":0,"duration":10,"fctrl":1,"cloud":1,"utc":1606456028,"type":"MQTT","fsrvid":"0%0","msg":"shake","rssi":-40,"scanenable":0}
At breakpoint B I look into my message buffer which should be NULLED from the memset but see it has the first character of the second message at index 154
image 2
I then step into function 'app_usbd_cdc_acm_read' as shown below
image 3
This shows that the message was received by the USB_CDC_ACM HAL layer okay but the index last_read is off by 1 byte thereby causing m_rx_buffer to be off by one and the 2nd byte of the sent message be in the first byte of my m_rx_buffer.
image 4
It looks like once the APP_USBD_CDC_ACM_USER_EVT_RX_DONE is hit, the first byte of the sent message has already been read by the HAL layer before function 'app_usbd_cdc_acm_read' has been executed.
Can you please fix this issue or suggest a way around it when processing APP_USBD_CDC_ACM_USER_EVT_RX_DONE events for messages greater than 64 bytes
Regards,
Jes
