topic Re: USB CDC Example Receive only fail in Kinetis Microcontrollers

USB CDC Example Receive only fail

etronic_arg — Tue, 01 Oct 2024 21:31:46 GMT

Hi,

I just trying to do a Virtual COM communication based on the USB CDC example from SDK.
I tested the example with success.

I cancel the "echo" part of the APPTask:

static void APPTask(void) { usb_status_t error = kStatus_USB_Error; if ((1 == s_cdcVcom.attach) && (1 == s_cdcVcom.startTransactions)) { /* User Code */ /* endpoint callback length is USB_CANCELLED_TRANSFER_LENGTH (0xFFFFFFFFU) when transfer is canceled */ if ((0 != s_recvSize) && (USB_CANCELLED_TRANSFER_LENGTH != s_recvSize)) { int32_t i; /* Copy Buffer to Send Buff */ for (i = 0; i < s_recvSize; i++) { s_currSendBuf[s_sendSize++] = s_currRecvBuf[i]; } s_recvSize = 0; } /* if (s_sendSize) { uint32_t size = s_sendSize; s_sendSize = 0; error = USB_DeviceCdcAcmSend(s_cdcVcom.cdcAcmHandle, USB_CDC_VCOM_BULK_IN_ENDPOINT, s_currSendBuf, size); if (error != kStatus_USB_Success) { // Failure to send Data Handling code here } } */

If I send "HELLO" wth a terminal from a PC, the first time s_currSendBuf fills with the characters.

With the second "HELLO" I send, the terminal stucks.

I just need to receive characters but not send them back.
What would be the right way to do it?

Thanks

Re: USB CDC Example Receive only fail

xiangjun_rong — Wed, 09 Oct 2024 02:48:14 GMT

Hi,

Can you tell us the part number you are using?

XiangJun Rong

Re: USB CDC Example Receive only fail

etronic_arg — Wed, 09 Oct 2024 13:21:09 GMT

Hello XiangJun,

The part I'm using is the MK27FN2M0VM115 in a custom board, but I also tested it in a FRDM-K64F.

I solve the issue partially calling the USB sending fuction without data after receiving:

if (s_sendSize) { uint32_t size = s_sendSize; s_sendSize = 0; error = USB_DeviceCdcAcmSend(s_cdcVcom.cdcAcmHandle, USB_CDC_VCOM_BULK_IN_ENDPOINT, NULL, 0); if (error != kStatus_USB_Success) { // Failure to send Data Handling code here } }

Is there a better solution?

Re: USB CDC Example Receive only fail

xiangjun_rong — Thu, 10 Oct 2024 06:15:35 GMT

Hi,

Yes, this is a good solution. After you have data, just call the the function to send.

Xiangjun Rong

USB_DeviceCdcAcmSend();