IOMUX and SPI2 on ESP32-S3

MattiaBerton
Posts: 13
Joined: Thu Aug 30, 2018 8:16 am

IOMUX and SPI2 on ESP32-S3

Postby MattiaBerton » Sat May 14, 2022 8:52 am

Hello,
I need to route the SPI2 to ESP32-S3 with two slave devices attached on it. From what I saw in the documentation, https://docs.espressif.com/projects/esp ... aster.html, the IOMUX have 1 CS shown. What about the other CS line? What are the other IOMUX pin used for SPI2 CS? Where can I find the IOMUX pin list?
Thank you,
Mattia Berton

ESP_Sprite
Posts: 6393
Joined: Thu Nov 26, 2015 4:08 am

Re: IOMUX and SPI2 on ESP32-S3

Postby ESP_Sprite » Sun May 15, 2022 1:42 am

Using the designated pins on the IOMUX is only needed in some circumstances when you need the absolute lowest latency and highest speed on your devices. For all other uses, you can assign any GPIO to any SPI signal using the GPIO matrix. As the CS signal usually is the slowest signal in SPI, you can also route CS2, CS3 etc via the GPIO matrix.

MattiaBerton
Posts: 13
Joined: Thu Aug 30, 2018 8:16 am

Re: IOMUX and SPI2 on ESP32-S3

Postby MattiaBerton » Sun May 15, 2022 10:08 pm

Thank you for your answer. Unfortunately, I need to go up to 80 MHz in my design, so IOMUX seems to be mandatory. What are the pin for IOMUX in SPI2? In case there are no CS available in IOMUX, can I have CS pins routed in GPIO matrix?

Thank you,
Mattia

ESP_Sprite
Posts: 6393
Joined: Thu Nov 26, 2015 4:08 am

Re: IOMUX and SPI2 on ESP32-S3

Postby ESP_Sprite » Mon May 16, 2022 1:42 am

The IOMUX pins are indicated in the datasheet by the pins demarked as FSPI*. I think the SPI master driver allows you to select a random pin as CS. Note that for 80MHz use, it may be possible to also use the GPIO matrix specifically on the S3; I seem to recall the digital team made some optimizations there, but you'd have to test that as I can't immediately find the details on that.

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