AUART RTS delay

chris321 — Thu, 24 Apr 2014 13:11:58 GMT

Hello Community,

I want to use the AUART0 of the i.MX28 with the handshake signals. For this I am using the latest stable Linux Kernel 3.14.1.

The AUART0 part of the device tree:

	auart0: serial@8006a000 {
	pinctrl-names = "default";
	pinctrl-0 = <&auart0_pins_a>;
	fsl,uart-has-rtscts;
	status = "okay";

};

So the device tree uses all four pins of this UART. In Linux itself I configure the interface with:

stty -F /dev/ttyAPP0 raw 9600 -echo -echoe -echok -echoctl -echoke crtscts

The UART and the handshake signals are working in principle. But I've noticed a delay between the RTS signal and the stopbit as you can see in the attached figure. I think that 13 ms are really unnecessary and I can not trace it back where they are from.

I tried this too:

stty -F /dev/ttyAPP0 raw 9600 -echo -echoe -echok -echoctl -echoke -crtscts

The bits CTSEN and RTSEN of the UARTAPP_CTRL2 register are toggled, but there is still a something similar on the RTS lines, but now it os no CTS needed.

So my questions are, where are this delays come from?

How can I be sure who is toggling the RTS line (Linux or the i.MX28 hardware module) ?

best regards

Re: AUART RTS delay

fabio_estevam — Thu, 24 Apr 2014 13:49:41 GMT

I would suggest you to post this into linux-arm-kernel and linux-serial mailing lists.

topic AUART RTS delay in i.MX Processors

AUART RTS delay

Re: AUART RTS delay