USB CDC ACM Example Single Write

RE: USB CDC ACM Example Single Write

Jørgen Holmefjord — Thu, 19 Apr 2018 07:20:34 GMT

Hi, please post a new thread where you described your issue in detail. Please also include which SDK version you are using. If you are not using latest SDK, please see if you can get it working using SDK 15.0.0.

RE: USB CDC ACM Example Single Write

Deepa Gopinath — Wed, 18 Apr 2018 14:18:10 GMT

Hi all,

I too face the same issue.

In our program calling app_usbd_cdc_acm_write() a single time does not directly send a message to the terminal program (Teraterm).
Even Teraterm is not getting connected to USB Port.Even though an APP_USBD_CDC_ACM_USER_EVT_TX_DONE is generated and the LED4 is changing its status.
After calling app_usbd_cdc_acm_write() the fourth time all four messages (the current one and the three from before) are visible on the computer.

I have observed this behaviour when Im in debug mode. But When I do free run , messages are not visible on the computer after 4th message.
In case of free run messages are visible on the computer after 20th message.

Can you please help to resolve this issue?

Thanks in Advance

Regards,

Deepa

RE: USB CDC ACM Example Single Write

Fabian — Fri, 28 Jul 2017 12:58:09 GMT

Thanks again, I will test it on monday!

RE: USB CDC ACM Example Single Write

Jørgen Holmefjord — Fri, 28 Jul 2017 12:06:41 GMT

Please check if this suggestion solves your problem.

RE: USB CDC ACM Example Single Write

Fabian — Thu, 27 Jul 2017 16:21:14 GMT

Hi Jørgen,

thanks for your answer.

In our program calling app_usbd_cdc_acm_write() a single time does not directly send a message to the terminal program (putty). Even tho an APP_USBD_CDC_ACM_USER_EVT_TX_DONE is generated and the LED4 is changing its status. After calling app_usbd_cdc_acm_write() the fourth time all four messages (the current one and the three from before) are visible on the computer.

Are we missing something?

Best regards

Fabian

RE: USB CDC ACM Example Single Write

Jørgen Holmefjord — Thu, 27 Jul 2017 12:37:24 GMT

Hi Fabian,

In the USB CDC ACM example, the state of the buttons are checked inside an endless while-loop inside main function. If the button is pressed, a write will be performed. If holding down the button, the loop will cause multiple writes.

If you want to write a single data array, you can call app_usbd_cdc_acm_write() anywhere in your code:

static uint8_t m_tx_buffer[NRF_DRV_USBD_EPSIZE * 16] = {'P','u','t',' ','d','a','t','a',' ','h','e','r','e','\r','\n','\0'};
app_usbd_cdc_acm_write(&m_app_cdc_acm, m_tx_buffer, sizeof(m_tx_buffer));

Best regards,

Jørgen