RPi4: 'Error 90 performing SPI data transfer.'

“Describe the bug” I’m trying to receive analog readings from an esp32 connected to my Raspberry Pi 4 over SPI. The code below works perfectly on an Raspberry Pi 3B+, but when I try to run the exact same code on a Pi 4 then adc_0.Read(tmp) gives me this “unGoogleable” error: Error 90 performing SPI data transfer. Does anyone have any idea what the problem might be?

C#-code: (.NET Core 3.1)

using System;
using System.Device.Spi;

namespace SPITest1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Hello World!");
            var spiTester = new SpiTester();
            var result = spiTester.Test1();
        }

    }

    public class SpiTester
    {
        SpiDevice adc_0;
        private readonly int clockFrequency = 10_000_000;//48_000_000; //48MHz;
        private readonly SpiMode spiMode = SpiMode.Mode3;
        private readonly int dataBitLength = 8;

        private ushort[] sampleArray;
        private byte[] tmp;

        public SpiTester()
        {
            sampleArray = new ushort[16 * 1000];
            tmp = new byte[16 * 1000 * 2];

            SpiConnectionSettings spiSettings_0 = new SpiConnectionSettings(0, 0)
            {
                ClockFrequency = clockFrequency,
                Mode = spiMode,
                DataBitLength = dataBitLength
            };

            adc_0 = SpiDevice.Create(spiSettings_0);
        }
        public ushort[] Test1()
        {
            Array.Clear(sampleArray, 0, sampleArray.Length);
            Array.Clear(tmp, 0, tmp.Length);

            adc_0.Read(tmp);

            for (int i = 0; i < sampleArray.Length; i++)
            {
                sampleArray[i] = (ushort)(tmp[i * 2 + 1] | tmp[i * 2] << 8);
            }

            return sampleArray;
        }
    }
}

Arduino-code:

#include <Arduino.h>
#include <SPI.h>
#include <ESP32DMASPISlave.h>

typedef union
{
    uint16_t Sample;
    struct 
    {
        uint8_t LowBits;
        uint8_t HighBits;
    } SampleBits;
}t16Byte;

const int numberOfChannels = 16;
const int numberOfSamples = 1000;
static const uint32_t BUFFER_SIZE = 2 * (numberOfChannels * numberOfSamples);

ESP32DMASPI::Slave slave;
uint8_t* spi_slave_tx_buf;

t16Byte analogReadings[numberOfChannels * numberOfSamples];

void setup() 
{
    Serial.begin(115200);
    spi_slave_tx_buf = slave.allocDMABuffer(BUFFER_SIZE);

    slave.setDataMode(SPI_MODE3);
    slave.setMaxTransferSize(BUFFER_SIZE);
    slave.setDMAChannel(2);
    slave.setQueueSize(1);
    
    // HSPI = CS: 15, CLK: 14, MOSI: 13, MISO: 12
    slave.begin(HSPI);

    for (uint16_t i = 0; i < (numberOfChannels*numberOfSamples); i++)
    {
        analogReadings[i].Sample = i;
    }    
}

void loop() 
{
    if (slave.remained() == 0)
    {
        Serial.printf("Sending data!\n");
        
        for (int sampleIndex = 0; sampleIndex < BUFFER_SIZE-1; sampleIndex +=2)
        {
            spi_slave_tx_buf[sampleIndex] = analogReadings[sampleIndex/2].SampleBits.HighBits;
            spi_slave_tx_buf[sampleIndex+1] = analogReadings[sampleIndex/2].SampleBits.LowBits;
        }
        slave.queue(NULL, spi_slave_tx_buf, BUFFER_SIZE);
        slave.yield();
        
        Serial.printf("Data sendt!\n");
    }
    delay(500);
}

Expected behavior adc_0.Read(tmp); should give me an array of data from my esp32.

Actual behavior adc_0.Read(tmp); throws the following error:

Exception has occurred: CLR/System.IO.IOException
An unhandled exception of type 'System.IO.IOException' occurred in System.Device.Gpio.dll: 'Error 90 performing SPI data transfer.'
   at System.Device.Spi.UnixSpiDevice.Transfer(Byte* writeBufferPtr, Byte* readBufferPtr, Int32 buffersLength)
   at System.Device.Spi.UnixSpiDevice.Read(Span`1 buffer)
   at SPITest1.SpiTester.Test1() in C:\Users\jesper.andersson\source\repos\SPITest1\SPITest1\Program.cs:line 46
   at SPITest1.Program.Main(String[] args) in C:\Users\jesper.andersson\source\repos\SPITest1\SPITest1\Program.cs:line 12

dotnet --info

.NET Core SDK (reflecting any global.json):
 Version:   3.1.102
 Commit:    573d158fea

Runtime Environment:
 OS Name:     raspbian
 OS Version:  10
 OS Platform: Linux
 RID:         linux-arm
 Base Path:   /home/pi/dotnet/sdk/3.1.102/

Host (useful for support):
  Version: 3.1.2
  Commit:  916b5cba26

.NET Core SDKs installed:
  3.1.102 [/home/pi/dotnet/sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.App 3.1.1 [/home/pi/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 3.1.2 [/home/pi/dotnet/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.1 [/home/pi/dotnet/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 3.1.2 [/home/pi/dotnet/shared/Microsoft.NETCore.App]

Version of System.Device.Gpio : “1.0.0”

[jesperandersson89]

Fixed it! The error comes from trying to read mode bytes than the SPI-buffer on Rasbian allows by default. (4096) The solution is either to create a file /etc/modprobe.d/spidev.conf with contents: options spidev bufsiz=65536 (or preferred buffer size). OR Add this to /boot/cmdline.txt: spidev.bufsiz=65536 (or preferred buffer size).

Reboot and check your work with cat /sys/module/spidev/parameters/bufsiz

Suggesting that someone fixes the cryptic error 90 that https://github.com/dotnet/iot/blob/master/src/System.Device.Gpio/System/Device/Spi/Devices/UnixSpiDevice.Linux.cs throws on line 227?

The problem here is Marshal.GetLastWin32Error(), because error 90 does not exist. Ref. https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--0-499-

Edit*: (Hmmm… error 90 is EMSGSIZE - “Message too long” in unix… so maybe I should have figured it out sooner?)

[joperezr]

Awesome I’m glad you found the issue and I thank you for posting the fix here so people in the future can come back to this if they ever hit it. Feel free to open an issue for fixing error messages from our API since I agree we should try to flush as much info as possible here.