QUERY · ISSUE

ports/esp32：a bug with Hardware SPI Initialize on ESP32-S3

openby EngineerWillopened 2022-12-16updated 2022-12-17

bugport-esp32

Hi,all:

Problem description and analysis

Hardware: ESP32S3
Firmware version: esp32/GENERIC_S3 v1.19.1 (2022-06-18) or master branch
Abstract: SPI(1) and SPI(2) need two initializations to work perfectly in each operation. If two initializations of different Baudrates are not carried out, SPI may not work.

code and pictures

Initialize with different baudrates()

self.spi = SPI(2,baudrate=4_000_000,polarity=0, phase=0,sck=Pin(SCK,Pin.OUT),mosi=Pin(MOSI,Pin.OUT))
self.spi = SPI(2,baudrate=8_000_000,polarity=0, phase=0,sck=Pin(SCK,Pin.OUT),mosi=Pin(MOSI,Pin.OUT))

Initialize with same baudrates(In order to reproduce the problem 100%, you also can initialize it once and run it again)

self.spi = SPI(2,baudrate=8_000_000,polarity=0, phase=0,sck=Pin(SCK,Pin.OUT),mosi=Pin(MOSI,Pin.OUT))
self.spi = SPI(2,baudrate=8_000_000,polarity=0, phase=0,sck=Pin(SCK,Pin.OUT),mosi=Pin(MOSI,Pin.OUT))

details

First time

I used the firmware V1.91.1 and found that SPI (1) initialization was abnormal. SPI(2) can work normally.
However, when I tried for the second time (after stop), I found that it could not work.
I tried to restart it and it could work again, but it still couldn't work the second time.
Then I tried various methods and accidentally found that baudrate could work after modification. So I conducted two initializations,The baudrate needs of the first initialization were different from that of the second initialization,The program could run perfectly, no matter whether it was STOP or not.

self.spi = SPI(2,baudrate=4_000_000,polarity=0, phase=0,sck=Pin(SCK,Pin.OUT),mosi=Pin(MOSI,Pin.OUT))
self.spi = SPI(2,baudrate=8_000_000,polarity=0, phase=0,sck=Pin(SCK,Pin.OUT),mosi=Pin(MOSI,Pin.OUT))

I found out that lssues #8634 suffers from a similar problem and saw the initialization issue solved in #9498

The second time

I tried to use the master branch to build a new firmware to try,
and then I found that SPI(1) and SPI(2) can be initialized normally and work, but the problem still exists that the initialization needs to be twice.

CANDIDATE · PULL REQUEST

ports/esp32/machine_sdcard.c: Fix ESP_ERR_INVALID_ARG on SDCard init on ESP32-S3 (Change DMA channel)

mergedby maripoopened 2023-01-13updated 2023-01-19

port-esp32

This pull request solves the problem that initialization of SDCard objects with SPI fails on ESP32-S3.

Problem

Creating SDCard object with SPI (slot=2 or 3) causes ESP_ERR_INVALID_ARG error.

[0;31mE (34340) spi: spi_bus_initialize(762): invalid dma channel, chip only support spi dma channel auto-alloc[0m
[0;31mE (34340) sdspi_host: spi_bus_initialize failed with rc=0x102[0m

The code below can reproduce this.

import os
from machine import Pin, SDCard

card = SDCard(slot=2, sck=Pin(17), miso=Pin(18), mosi=Pin(16), cs=Pin(15)) # <- ESP_ERR_INVALID_ARG

Reason

In ports/esp32/machine_sdcard.c, SPI slot configurations are defined. However, the DMA channel specified in the configuration for ESP32-S3 is inappropriate. In ESP-IDF, the only available channel for ESP32S3 is SPI_DMA_CH_AUTO=3.

esp-idf/components/driver/spi_common.c

Solution

Specifying DMA channel 3 instead of 2 fixes the problem. I have confirmed the problem and the solution on ESP32-S3-DevKitC-1 board.