SPI not working Raspberry Pico

[steeley]

Have used SPI.h with Arduino and similar boards (Mostly Teensy 3.2/4) with various digital pots, swipes EEProms and all my code works fine.

Nothing appears to work using SPI on RPI Pico. :(

The code below controls a digital pot - works perfectly on every board I have tried. On Pico SPI signals appear to do nothing
Software defined CS line seems to be a square wave at 50Hz!!!.

I've tried setting the pins before initing the library( SPI.setTX(SPI_MOSI_PIN). etc but that seems to produce some signals
but they are just wrong, or not there.

#include <SPI.h>

const int slaveSelectPin = 10;
//other pins as default:  GP18=CLK GP19=TX for Pico. 13=CLK 11=TX for Teensy 4
void setup() {

  pinMode (slaveSelectPin, OUTPUT);
  SPI.begin();
  delay(500);
//SPI_CLOCK_DIV4 = 0
  //setup pot registers
  SPI.beginTransaction(SPISettings(0, MSBFIRST, SPI_MODE1));
  digitalWrite(slaveSelectPin,LOW);
  SPI.transfer(0x18);
  SPI.transfer(0x02);
  digitalWrite(slaveSelectPin,HIGH);
  SPI.endTransaction();
}

void loop() {
  unsigned int val;
  for (val = 10; val <= 500; val++) {
    digitalPotWrite(1024-val);
    delay(10);
  }
  for (val = 500; val > 10; val--) {
    digitalPotWrite(1024-val);
    delay(10);
  } 
}

void digitalPotWrite(unsigned int val) {
  SPI.beginTransaction(SPISettings(0, MSBFIRST, SPI_MODE1));
  digitalWrite(slaveSelectPin, LOW);
  byte highbyte = (val >> 8) + 0x04; //high wiper byte + command
  byte lowbyte = val & 0xFF;
  SPI.transfer(highbyte); //send wiper data high byte
  SPI.transfer(lowbyte); //send wiper data low byte
  digitalWrite(slaveSelectPin, HIGH);
  SPI.endTransaction();
}

[earlephilhower]

SPI most assuredly does work, at least well enough for myself and lots of other folks to interface displays and related stuff.

There is a debug SPI mode setting, enable it and set the debug port itself to Serial and re-run your tests to collect some information on what's being done in the core.

Off the bat, I think the 0 Hz max clock is causing your grief. Set it to 100000 or something (whatever the max SPI rate is for your devices) and retry.

[earlephilhower]

In fact, we take the max speed you pass in and send it directly to the SDK which is probably only able to give a 50hz SPI clock as its lowest speed.

arduino-pico/libraries/SPI/SPI.cpp

Line 191 in 1fdc0ab

spi_init(_spi, _spis.getClockFreq());

So, I do think changing 0 to the proper max speed of your devices will get things rolling.

[steeley]

Ok the issue with this library seems to be the CS line. In the code below I'm using software CS and it works.if I use hardware the line does nothing.
As you say there are many people using this successfully., perhaps you could point me to. a code example that shows this working.( on a Pico) I've not found any unfortunately.

`#include <SPI.h>
//#include <Arduino.h>

const uint8_t SPI_MISO = 16;
const uint8_t SPI_CS = 22; //17 Pico hardware default
const uint8_t SPI_SCK = 18;
const uint8_t SPI_MOSI = 19;
//

SPISettings parSPI(10000, MSBFIRST, SPI_MODE1);

void setup() {
Serial.begin(115200);
pinMode(22,OUTPUT);
//---- Define the SPI pins -------
SPI.setRX(SPI_MISO);
SPI.setTX(SPI_MOSI);
SPI.setSCK(SPI_SCK);
//SPI.setCS(SPI_CS);
SPI.begin();

//setup pot registers
SPI.beginTransaction(parSPI);
digitalWrite(SPI_CS,LOW);
SPI.transfer(0x18);
SPI.transfer(0x02);
digitalWrite(SPI_CS,HIGH);
SPI.endTransaction();
}

void loop() {
unsigned int val;
for (val = 10; val <= 500; val++) {
digitalPotWrite(1024-val);
delay(10);
}
for (val = 500; val > 10; val--) {
digitalPotWrite(1024-val);
delay(10);
}
}

void digitalPotWrite(unsigned int val) {
SPI.beginTransaction(parSPI);
digitalWrite(SPI_CS, LOW);
byte highbyte = (val >> 8) + 0x04; //high wiper byte + command
byte lowbyte = val & 0xFF;
SPI.transfer(highbyte); //send wiper data high byte
SPI.transfer(lowbyte); //send wiper data low byte
digitalWrite(SPI_CS, HIGH);
SPI.endTransaction();
}`

[earlephilhower]

The Adafruit graphics libraries and even the included SD card libraries use SPI, so you can look there. The WizNet W5100S-Pico also uses SPI to connect to the onboard TCP chip.

[steeley]

Got a colleague to try running SPI on a Pico and they got the same result.
Switched to a different SPI library and the Pico works perfectly again. Not going to waste anymore of your/my time on this.
Going with Mbed or back to our usual stm32 stuff.