nRF5340 multiple high-speed SPI slaves

RE: nRF5340 multiple high-speed SPI slaves

tdoodnauth-g — Thu, 03 Jul 2025 14:35:36 GMT

Hello, I have a follow up question. Is there a max or recommended capacitance for the HS SPI interface?

We are noticing poor waveforms when using the HS SPI interface at 16 MHz.

RE: nRF5340 multiple high-speed SPI slaves

skruffen — Wed, 03 Apr 2024 07:35:53 GMT

Thank you for the help.

I have a better understanding now.

RE: nRF5340 multiple high-speed SPI slaves

Simonr — Wed, 03 Apr 2024 07:28:57 GMT

I heard back from the developers today, an here are their thoughts:

Since CSN is considered a "slow" signal in the sense of an SPI transfer, the use of a regular GPIO with software control is possible. The HW CSN offers tighter timing control (typically selecting slaves closer to the actual transaction). Another option to change between SPI slaves would be to disable the SPIM, change PSEL.CSN to the new slave and re-enable the SPIM.

The limitation for using several SPI slaves with high-speed SPI is not so much the CSN but rather the load on the SCK, MISO and MOSI pins. Each additional SPI slave with its PCB routing will add capacitive load and affect the waveforms.

Best regards,

Simon

RE: nRF5340 multiple high-speed SPI slaves

Simonr — Tue, 19 Mar 2024 08:34:30 GMT

Nothing as of yet I'm afraid, but I have pinged the internal case for an update now, and will keep pinging now and again until I hear something.

Best regards,

Simon

RE: nRF5340 multiple high-speed SPI slaves

skruffen — Mon, 18 Mar 2024 10:31:12 GMT

Are there any updates on this issue?

RE: nRF5340 multiple high-speed SPI slaves

Simonr — Tue, 05 Mar 2024 08:48:19 GMT

An internal ticket has been created on this issue. It might take a few days before I hear back from them, but I'll let you know as soon as I hear something.

Best regards,

Simon

RE: nRF5340 multiple high-speed SPI slaves

skruffen — Mon, 04 Mar 2024 10:32:17 GMT

Thank you.

It would be great if you could ask internally.

RE: nRF5340 multiple high-speed SPI slaves

Simonr — Mon, 04 Mar 2024 10:28:56 GMT

The nRF5340 is only designed for having one HSPI slave connected to it, yes. If you'd like I can ask internally if there are any ways around it, but I don't think so, since the high speed pins have different rise/fall times than the standard GPIOs.

Let me know if you'd like me to ask internally, as this has not been tested on our end AFAIK.

Best regards,

Simon