SPI on SAMD21G18 not working

Official Hardware Nano Family Nano 33 IoT
1

Hello,

I've been attempting to use SERCOM2 SPI Master on the SAMD21G18J but have been unsuccessful. I tried the configurations with SERCOM0 and SERCOM4, and they both worked. The most intriguing behavior is that when I initialize the SERCOM2 SPI, all of the other I/O pins stop working as well. The clock is not generated, and CS is not operational.

I tried several bootloaders, but the results were the same. To begin, I used the bootloader of an Arduino nano IOT 33, which uses the same chip, in order to use the arduino IDE more easily. Then, I tested with the bootloaders Arduino zero and adafruit M0 bootloader. The idea of testing other bootloarders was because arduino ano iot 33 uses SPI SERCOM2 to communicate with his WIFI module, and could be protected some how. Any insight will be useful.

The schematic is displayed below:

image
image822×527 137 KB

The SERCOM2 Pads:
image

Main routine:

// inslude the SPI library:
#include <SPI.h>
#include "SercomSPISlave.h"

SercomSPIMaster Spi2;

void setup() {

 
  PORT->Group[PORTA].DIR.reg |= PORT_PA08; // Output set wifi ctrl
  PORT->Group[PORTA].OUT.reg &= ~PORT_PA08;  // Turn OFF wifi
  // PORT->Group[PORTA].OUTCLR.reg |= PORT_PA08; 

  PORT->Group[PORTA].DIR.reg |= PORT_PA04;  // set output Group; Turn-On Circuit;
  PORT->Group[PORTA].OUT.reg |= PORT_PA04;
  PORT->Group[PORTA].OUTSET.reg |= PORT_PA04; // Turn ON

  PORT->Group[PORTA].DIR.reg |= PORT_PA14;  // set CS output
 

  pinMode(4, OUTPUT);




  // set the slaveSelectPin as an output:
  pinMode (slaveSelectPin, OUTPUT); //spi1
  // initialize SPI:
  Spi2.Sercom2Masterinit(); //spi2
 

}



void loop() {

  char c='z', r;
  PORT->Group[PORTA].OUT.reg &= ~PORT_PA14;  // Turn OFF wifi

 
  delay(100);
  // send in the address and value via SPI:
  r= Spi2.transfer2(c); //spi1
  Serial.println(r);

  delay(100);
 
  // take the SS pin high to de-select the chip:
  PORT->Group[PORTA].OUTSET.reg |= PORT_PA14; // Turn ON; unset pin
 
 
  //delay(1000);
 
}

Header file:

void SercomSPIMaster::Sercom2Masterinit(){

  
  PORT->Group[PORTA].DIR.reg &= ~PORT_PA13; //Set  as input (MISO)
  PORT->Group[PORTA].DIR.reg |= PORT_PA15; //Set  as output (SCK)
  PORT->Group[PORTA].DIR.reg |= PORT_PA14; //Set  as output (SS)
  PORT->Group[PORTA].DIR.reg |= PORT_PA12; //Set  as output (MOSI)
  
 
  pin_set_peripheral_function(PINMUX_PA15C_SERCOM2_PAD3);
  pin_set_peripheral_function(PINMUX_PA14C_SERCOM2_PAD2);
  pin_set_peripheral_function(PINMUX_PA13C_SERCOM2_PAD1);
  pin_set_peripheral_function(PINMUX_PA12C_SERCOM2_PAD0);

    
  //PAGE 492 26.8.1 Control A - ref B
  SERCOM2->SPI.CTRLA.bit.ENABLE =0; //Disable SPI 1
  while(SERCOM2->SPI.SYNCBUSY.bit.ENABLE); // Wait sync
 
  //Reset SPI 1
  SERCOM2->SPI.CTRLA.bit.SWRST = 1;
  while(SERCOM1->SPI.CTRLA.bit.SWRST || SERCOM1->SPI.SYNCBUSY.bit.SWRST); // Wait sync
 
  //Setting Generic Clock Controller!!!!
  GCLK->CLKCTRL.reg = GCLK_CLKCTRL_ID(GCM_SERCOM1_CORE) | //Generic Clock 0
            GCLK_CLKCTRL_GEN_GCLK0 | // Generic Clock Generator 0 is the source
            GCLK_CLKCTRL_CLKEN; // Enable Generic Clock Generator
 
  while(GCLK->STATUS.reg & GCLK_STATUS_SYNCBUSY); //Wait for synchronisation
 
  //Set up SPI Control A Register
  SERCOM2->SPI.CTRLA.bit.DORD = 0; //MSB first
  SERCOM2->SPI.CTRLA.bit.CPOL = 0; //SCK is low when idle, leading edge is rising edge
  SERCOM2->SPI.CTRLA.bit.CPHA = 0; //data sampled on leading sck edge and changed on a trailing sck edge
  SERCOM2->SPI.CTRLA.bit.FORM = 0x0; //Frame format = SPI

  // Choose PAD configuration
  SERCOM1->SPI.CTRLA.bit.DIPO = 0x1; //DATA PAD1 MISO is used as Master input (slave mode) // page 492
  SERCOM1->SPI.CTRLA.bit.DOPO = 0x3; //DATA PAD0 MOSI is used as Master output and PAD3 as SCK

  SERCOM2->SPI.CTRLA.bit.MODE = 0x3; //SPI in Master mode
  SERCOM2->SPI.CTRLA.bit.IBON = 0x1; //Buffer Overflow notification
  SERCOM2->SPI.CTRLA.bit.RUNSTDBY = 1; //wake on receiver complete
 
  //Set up SPI control B register
  SERCOM2->SPI.CTRLB.bit.RXEN = 0x1; //Enable Receiver
  //SERCOM2->SPI.CTRLB.bit.SSDE = 0x1; //Slave Selecte Detection Enabled
  SERCOM2->SPI.CTRLB.bit.CHSIZE = 0; //character size 8 Bit
 
  //SERCOM1->SPI.CTRLB.bit.PLOADEN = 0x1; //Enable Preload Data Register
  //while (SERCOM1->SPI.SYNCBUSY.bit.CTRLB); 
 
  //Set Baud rate
  uint16_t BAUD_REG = ((float)SPI_CLK_FREQ / (float)(2 * SPI_BAUD)) - 1;  //Calculate BAUD value For Sync
  SERCOM2->SPI.BAUD.reg =  SERCOM_SPI_BAUD_BAUD(BAUD_REG);       //Set the SPI baud rate
  SERCOM2->SPI.CTRLA.reg |= SERCOM_SPI_CTRLA_ENABLE;         //Enable the Sercom SPI
  while(SERCOM2->SPI.SYNCBUSY.bit.ENABLE);   
 

  //Enable SPI
  SERCOM2->SPI.CTRLA.bit.ENABLE = 1;
  while(SERCOM2->SPI.SYNCBUSY.bit.ENABLE);
  SERCOM2->SPI.CTRLB.bit.RXEN = 0x1; //Enable Receiver, this is done here due to errate issue
  while(SERCOM2->SPI.SYNCBUSY.bit.CTRLB); //wait until receiver is enabled

};



uint8_t SercomSPIMaster::transfer2(uint8_t data)
{
  while(SERCOM2->SPI.INTFLAG.bit.DRE == 0);
  SERCOM2->SPI.DATA.reg = data;
  while(SERCOM2->SPI.INTFLAG.bit.RXC == 0);
  return (uint8_t)SERCOM2->SPI.DATA.reg;
}
2

Good morning,
As I had the same problem with nano iot 33 I wrote here. I am going to send temperature of a sensor via arduino nano iot33 and dragino lora sheild (module) to TTN, but after uploading LMIC lib to the board the port loose and board disconnect. but it works properly with arduino uno. As I discovered there is problem with SPI pins in arduino iot33 as it doesnt have SPI.
May I ask your helps how can I define SPI in my LMIC library example?
this way is ok?

SPI.setMOSI(PA6);
SPI.setMISO(PA4);
SPI.setSCLK(PA20);
os_init();
// Reset the MAC state. Session and pending data transfers will be discarded.
LMIC_reset();

3

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