UART4 APALIS imx6

Technical Support
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21

Hi @henrique.tx

You say that your DTS looks as follow:

&uart4 {
pinctrl-0 = <&pinctrl_uart4_dte>;
status = “okay”;
};

&pinctrl_uart4_dte {
fsl,pins = <
MX6QDL_PAD_CSI0_DAT13__UART4_TX_DATA 0x1b0b1
MX6QDL_PAD_CSI0_DAT12__UART4_RX_DATA 0x1b0b1
MX6QDL_PAD_CSI0_DAT17__UART4_RTS_B 0x1b0b1
MX6QDL_PAD_CSI0_DAT16__UART4_CTS_B 0x1b0b1
>;
};

But property uart-has-rtscts is missing. Are you sure you are using hardware
flow control during communication?

Thanks

22

Hi @henrique.tx
we saw that you use this PINs for tx and rx in APALIS: pin 185 (tx–> CSI0_DATA13) and pin 187(rx → CSI0_DATA13 )

But we are using pin 134(tx–> KEY_ROW0) and pin 136(rx–> KEY_COL0).

So we need the solution with our configuration on board.

A VERY IM PORTANT QUESTION: are PINS 185 and 187 necessary in order to make the serial work?? Can we use our pins for tx and rx??

Thanks

23

Hi @AiLux, how are you?

@henrique.tx is currently in vacation. I’ll reproduce his setup on my side to check for the following:

I’ll come back to you up to Thursday on this topic.

About your other question:

The answer is no. If you look at the datasheet (https://docs.toradex.com/101770-apalis-imx6-datasheet.pdf) table 5-33 you can see that these pins could also be used as RX/TX. They were the chosen ones due to availability on his setup but it should work normally with pins 134 and 136.

24

Dear @AiLux,

I tested the following change to Henrique’s device tree:

&uart4 {
 pinctrl-0 = <&pinctrl_uart4_dte>;
+ uart-has-rtscts;
 status = "okay";
 };

And I’ve been able to communicate with both modules as he did. I could also see an RTS/CTS signal being sent on the logic analyser.

Have you tried to use a similar device tree on your side?

Best regards,

25

Yes, we tried but it doesn’t work.

We cannot test on pins 185 and 187 to verify that it works exactly like you do. On pins 134 and 136 in every test and configuration still does not work and this suggests that these pins cannot be used with hardware flow control.

We have decided to make a hardware change to our board.
We used UART2 instead of UART3. This modification takes a lot of work but we have verified that the UART2 works with the hardware flow control without any problems.

Thanks for your support.

26

Hi @AiLux,

Thanks for the update. I’ll forward this to our team for them to check if there could a problem with these two specific pins as we’ve been able to control them with pins 185 and 187. I’m sorry that you need to pass through this rework.

Please feel free to come back again if you have any other issues, we’ll be glad to help.

Best regards,