topic Re: Output pin not going high in S32K

Output pin not going high

m_mishrikey — Thu, 15 Dec 2022 04:20:39 GMT

MCU: S32K148 144 pin

I have a GPIO pin that I wish to drive high.

The pin is connected with a 3.3k resistor to ground.

I expect the push-pull output to be able to drive this pin high, however it seems the 3.3k is pulling the line to ground. The line goes up but immediately decays back to low.

In the PEX config, the pin is clearly set to have pull-up/pull-down disabled. Init value is high, but I also force high in the main function.

Re: Output pin not going high

Senlent — Thu, 15 Dec 2022 07:38:07 GMT

Hi@m_mishrikey

There is nothing wrong with your settings, it should be that the drive capacity is not enough, maybe you can remove the external pull-down resistor, or increase the pull-down resistor, such as 10K or larger.

Re: Output pin not going high

m_mishrikey — Thu, 15 Dec 2022 16:26:07 GMT

I don't follow. The spec says for a 3.3V rail, the outputs can source up to 3.5mA. For a 3.3k external pull-down, that is only 1mA. I would expect the output can recover even if the output capacitance is not sufficient.

I'm not loading the other outputs down heavily either, in case there was a question about total output over all ports.

Re: Output pin not going high

Senlent — Fri, 16 Dec 2022 03:29:05 GMT

Hi@m_mishrikey

please confirm again:

1.you already set the ptc14 like this,

2.measure whether the resistance value of the pull-down resistor is 3.3K

If there is nothing wrong with the above, I will test it on myside.

Re: Output pin not going high

m_mishrikey — Fri, 16 Dec 2022 04:00:45 GMT

Yes, PTC14 is set to output in Routing tab, and Pull Enable is disabled in Functional Properties tab. PEX is regenerated and program is rebuilt and programmed. Finally, pull-down measures 3.3k.

Re: Output pin not going high

Senlent — Fri, 16 Dec 2022 04:06:18 GMT

Ok, I'll do a similar test and I'll send you the results,
If the phenomenon is the same, it only shows that the driving ability is insufficient

Re: Output pin not going high

Senlent — Mon, 19 Dec 2022 02:46:37 GMT

Hi@m_mishrikey

I did a drive capability test on the S32K142. The tested port is PTB0, and the pull-down resistance ranges from 390 to 3.3K. Within these ranges, the output can be kept in a high state (I didn’t test the working condition below 390Ω, and the chip’s power supply is 5V).

I think the driving ability should be able to cover this working condition, the only thing to pay attention to is this sentence in the data sheet:

IOHT Output high current total for all ports — — 100 mA

Re: Output pin not going high

m_mishrikey — Mon, 19 Dec 2022 15:35:55 GMT

Case of "toothache that went away". I remeasured today and the pin is driving fine. I can't explain it.

Sorry for the trouble, and thank you for checking.