topic Re: UART Communication Directly Between Two S32K1xx MCUs in S32K

UART Communication Directly Between Two S32K1xx MCUs

hongpingxu-b364 — Thu, 14 Jul 2022 10:37:19 GMT

Hi,

My customer use two S32K1xx MCU on one board, and connect directly with UART.

Customer found that UART communication will be failed if no external pull-up. Customer wonder whether the external pull-up is mandatory 佛如direct connection application?

BR,

Hornby

Re: UART Communication Directly Between Two S32K1xx MCUs

Robin_Shen — Fri, 15 Jul 2022 03:55:59 GMT

Hi Hornby,

Whether the customer's application software these two cases:

Just add external pull-up resistor to make UART communication normal?

What value is set in the PORT_PCRn register of the LPUART_RX pin?

If the internal pull-up resistor is enabled, is it possible to have the same phenomenon as using an external pull-up resistor?

Are two S32K1xx chips powered on at the same time? Is one of the chips not working at all, or is it just the LPUART communication part that is not working?

Please tell me the part number and mask set of two S32K1xx.

Best Regards,
Robin
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Re: UART Communication Directly Between Two S32K1xx MCUs

hongpingxu-b364 — Fri, 15 Jul 2022 04:40:43 GMT

Hi Robin,

Thanks for your reply.

Customer used S32K144 and S32K116 with last Maskset, and only configured MUX bitfield on PORT_PCRn register. Just add external pull-up resistor to make UART communication normal.

These two S32K1xx chips are powered on the same supply. The first UART message send around 2s after power on, so customer make sure that these two S32K1xx MCU are finished initialization already.

We also push them to enable internal pull-up, but customer wonder 1.) why old solution with STM32 and same configure can work properly; 2.) S32K1 internal pull-up/down are weak pull, customer oppugned the communication reliability.

Best regards,

Hornby

Re: UART Communication Directly Between Two S32K1xx MCUs

Robin_Shen — Fri, 15 Jul 2022 09:55:40 GMT

I don't have S32K144EVB on hand, so just test it on S32K146EVB and S32K116EVB. Modify the lpuart_echo example in S32K1xx SDK RTM v4.0.2, change the pins in order to connect directly.

S32K146EVB default modified
LPUART1_TX PTC7 PTC9 J6 16
LPUART1_RX PTC6 PTC8 J6 13

S32K116EVB default modified
LPUART0_TX PTB1 PTA3 J1 2
LPUART0_RX PTB0 PTA2 J1 1

It was able to communicate normally. So would you please let customer check their circuit?(common ground?)

These pins only configured MUX bitfield on PORT_PCRn register. Did not enable the internal pull-up resistor.