SPI limiting esp32s3 to a baud rate of 800,000

[MATTYGILO]

I am using this code on an esp32s3

baudrate = 40_000_000
spisd = SoftSPI(baudrate= baudrate, sck=sck.pin, mosi=mosi.pin, miso=miso.pin)
print("Using SPI: {}".format(spisd))

Outputs:

Using SPI: SoftSPI(baudrate=800000, polarity=0, phase=0, sck=12, mosi=11, miso=13)

As you can see 800_000 != 40_000_000

When I use a value < 800_000. For example 200_000.

SoftSPI(baudrate=166666, polarity=0, phase=0, sck=12, mosi=11, miso=13)
166_666 is close to the value of 200_000.

Conclusion: Micropython is limiting the ESP32S3 to a baud rate of 800_000

All help is much appreciated, thanks in advance

[robert-hh]

SoftSPI is, what it says: SPI implemented in software. Given that the CPU runs at 160MHz, you cannot expect a 40MHz baudrate. And generally for SPI the baud rates cannot be precise. Did you try the same with hardware SPI? The SPI hardware is clocked from a 160MHz clock, AFAIK. There, 40Mhz or even 80Mhz are accepted as input value.
Edit: Tested with a scope: SCK is 80 MHz or 40MHz, when set so.

[MATTYGILO]

@robert-hh Yes I have tried normal SPI also, makes no difference

And micropython also just says:

Warning: SPI(-1, ...) is deprecated, use SoftSPI(...) instead

[robert-hh]

Warning: SPI(-1, ...) is deprecated,

SPI(-1. ...) was used to denote SoftSPI. So with SPI(-1, ...) you still got SoftSPI. For hard SPI, use e.g. SPI(0, ....) or SPI(1, .....). And I checked with the oscilloscope, that with hard SPI SCK is indeed 40Mhz, if selected.

[MATTYGILO]

@robert-hh What ID should I use in micropython for SPI pins 11-13

[robert-hh]

That's SPI(0). If you write:

from machine import SPI
spi=SPI(0, baudrate=40_000_000)
print(spi)

it will show you which pins are used.

[MATTYGILO]

@robert-hh So I tried the suggestion but get this error?

ValueError: SPI(0) doesn't exist

[MATTYGILO]

Seems that those configuration for the pins are not currently available in micropython for the ESP32S3

micropython/ports/esp32/machine_hw_spi.c

Line 73 in 9e6885a

#elif CONFIG_IDF_TARGET_ESP32S2 || CONFIG_IDF_TARGET_ESP32S3

https://github.com/micropython/micropython/blob/9e6885ad820a9f42bf93df56eb3f3be0c8639622/ports/esp32/boards/GENERIC_S3/mpconfigboard.h

Chat GPT:

Based on the pin assignments you provided in your previous message (Pin 13 for MISO, Pin 11 for MOSI, Pin 12 for SCLK, and Pin 10 for CS), it seems that you are using a non-standard pin mapping, which may not align with the default SPI bus numbering in MicroPython for ESP32S3.

[robert-hh]

I see, I used SPI(1) on a Lolin S3 boards.

From the answer of ChatGPT It sounds as if it went into politics: many words but no answer,

[MATTYGILO]

I've added:

#define MICROPY_HW_SPI1_SCK (12)
#define MICROPY_HW_SPI1_MOSI (11)
#define MICROPY_HW_SPI1_MISO (13)

To my mpconfigboard.h. Going to see if it makes any difference

[MATTYGILO]

I tried SPI2 version, but it failed also

[beyonlo]

I tried SPI2 version, but it failed also

@MATTYGILO What MicroPython version are you using? here the SPI(1) and SPI(2) works, but SPI(0) fail:

>>> import os
>>> os.uname()
(sysname='esp32', nodename='esp32', release='1.19.1', version='v1.19.1-966-g05bb26010 on 2023-03-13', machine='ESP32S3 module (spiram) with ESP32S3')
>>> from machine import SPI
>>> spi=SPI(0, baudrate=40_000_000)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: SPI(0) doesn't exist
>>> 
>>> spi=SPI(1, baudrate=40_000_000)
>>> print(spi)
SPI(id=1, baudrate=40000000, polarity=0, phase=0, bits=8, firstbit=0, sck=12, mosi=11, miso=13)
>>> spi=SPI(2, baudrate=40_000_000)
>>> print(spi)
SPI(id=2, baudrate=40000000, polarity=0, phase=0, bits=8, firstbit=0, sck=36, mosi=35, miso=37)
>>> spi=SPI(3, baudrate=40_000_000)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: SPI(3) doesn't exist
>>>