SPI MISO seems to be pulled down in NCS

RE: SPI MISO seems to be pulled down in NCS

Mandrii — Tue, 25 May 2021 09:21:00 GMT

We fixed the problem.

It was completely on our software side: second SPI CS pin was active in the new firmware, while I tested another pin.

Thanks for your help anyway 🙏🏻

RE: SPI MISO seems to be pulled down in NCS

Mandrii — Tue, 25 May 2021 08:50:55 GMT

[quote userid="2115" url="~/f/nordic-q-a/75550/spi-miso-seems-to-be-pulled-down-in-ncs/311345#311345"]For no pull, remove the "miso-pull-*" in your DT overlay, and recompile.[/quote]

Tried that. Originally, there were no "miso-pull" options in my DTS file.

[quote userid="2115" url="~/f/nordic-q-a/75550/spi-miso-seems-to-be-pulled-down-in-ncs/311345#311345"]its important that you verify this by reading the register:[/quote]

I am getting:

$ nrfjprog --memrd 0x1000120c -f nrf52
0x1000120C: FFFFFFFE

– looks correct.

[quote userid="2115" url="~/f/nordic-q-a/75550/spi-miso-seems-to-be-pulled-down-in-ncs/311345#311345"]Have you tried reducing the frequency of the SPIM to see if this has an impact on the read data?[/quote]

Yes, SPI clock speed is at the minimum (125 kHz).

[quote userid="2115" url="~/f/nordic-q-a/75550/spi-miso-seems-to-be-pulled-down-in-ncs/311345#311345"]are you using the nRF52840-DK for testing?[/quote]

No, we are using our custom board with MS88SF2 v1.0 module.

[quote userid="2115" url="~/f/nordic-q-a/75550/spi-miso-seems-to-be-pulled-down-in-ncs/311345#311345"]Does this issue happen on more than one board?[/quote]

Unfortunately, we have only one custom dev board of this kind for now. Because it works fine with different firmware (the one compiled with nRF5 SDK for Thread and Zigbee) we didn't think that the board could have an issue. But we will look into that too.

RE: SPI MISO seems to be pulled down in NCS

Håkon Alseth — Tue, 25 May 2021 08:15:54 GMT

Hi,

[quote user=""]Is there a fix for this? Can I disable pulldown? Is there a "no pull" option for MISO in NCS?[/quote]

For no pull, remove the "miso-pull-*" in your DT overlay, and recompile.

[quote user=""]For MISO, I am using pin P0.09. (CONFIG_NFCT_PINS_AS_GPIOS=y is set in prj.conf.)[/quote]

its important that you verify this by reading the register:

https://infocenter.nordicsemi.com/topic/ps_nrf52840/uicr.html?cp=4_0_0_3_4_0_5#register.NFCPINS

via nrfjprog:

nrfjprog --memrd 0x1000120c -f nrf52

[quote user=""]nRF52840 side is reading all zeroes (ADC chip is separated from nRF by a digital isolator ISO772x). When I connect VCC to MISO with a wire however, the software can read all ones instead of zeroes (so SPI is working). [/quote]

This is quite strange. Have you tried reducing the frequency of the SPIM to see if this has an impact on the read data?

Does this issue happen on more than one board?

PS: are you using the nRF52840-DK for testing? If yes, then the P0.09/P0.10 GPIOs are not routed by-default to the pin headers. You then need to connect some solder bridges:

https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/hw_nfc_if.html?cp=4_0_4_7_10

Kind regards,

Håkon