UART Transmission Issue

RE: UART Transmission Issue

Einar Thorsrud — Tue, 23 Nov 2021 15:19:55 GMT

Can you elaborate? Also, you should ensure you call uart_irq_tx_ready() and that it returns 1 before you call uart_fifo_fill().

RE: UART Transmission Issue

jdorn — Mon, 22 Nov 2021 16:44:16 GMT

I tried that, and using either one of or both tx_ready or tx_enable functions completely prevent me from transmitting messages.

RE: UART Transmission Issue

Einar Thorsrud — Fri, 12 Nov 2021 11:28:57 GMT

Hi,

I have not had a chance to test this but I notice you call uart_fifo_fill() without first calling uart_irq_tx_ready(), and from each others event handlers, and that is not how the API is intended to be used. See the uart_fifo_fill() API documentation.

RE: UART Transmission Issue

jdorn — Wed, 10 Nov 2021 21:27:20 GMT

Hello,

I have determined that

uart_fifo_fill(uart2, sendbuf, strlen(sendbuf));

is the offending line of code. for some reason, when I call that function the first time, it succeeds. but the second time (and every time after) it always returns 0 bytes sent and does not transmit any data. note: I have verified that both the buffer is populated and the strlen() function returns the expected value via debugging.

the only way i have found to fix this problem is to receive data on the uart 2 fifo_read function. this resets whatever is blocking the fifo_fill and allows another item to be sent.

note: the other device (uart 1) does not have a similar issue.

RE: UART Transmission Issue

jdorn — Wed, 10 Nov 2021 15:15:04 GMT

Overlay: just changes pins of uart 1 and uart 2. enables them and sets their speed to 9600.

&uart1 {
	status = "okay";
	current-speed = <9600>;
	tx-pin = <13>;
	rx-pin = <14>;
};

&uart2 {
	status = "okay";
	current-speed = <9600>;
	tx-pin = <15>;
	rx-pin = <16>;
};

&i2c2 {
	status = "disabled";
};

I have two external usb->uart devices (I am using diligent's PmodUSBUART board. I have tested other usb->uart devices and confirmed that it is not a hardware issue).

These usb->uart boards connect between my PC and my DK on UART 1 and UART 2.

I am using the serial console built in to XCTU on the PC to monitor the uart->usb devices on the PC side.

RE: UART Transmission Issue

Einar Thorsrud — Wed, 10 Nov 2021 14:49:37 GMT

Hi,

I am not able to explain this right now. Can you share everything I need to reproduce on my end, so also your device tree overlay, and if there are any other things that are also needed?