Serial USB crashes on SAMD21

Other Hardware 3rd Party Boards
1

Hi, I'm developing a product based on Arduino. Since it's a custom product I have created a new board definition file to use with an existing bootloader. The MCU used is ATSAMD21E18A. The issue is that when I enable SerialUSB and turn off some I/O the MCU crashes. Once it happens it no longer appear as a COM port and I need to reupload the bootloader to recover from this. I have spent days trying to figure out where the issue is. I have tested the hardware using a seperate C code and it works fine. Therefore, it is definitely a software issue.

The varinat.cpp file as below

#include "variant.h"


// Pins descriptions
// ------------------------
const PinDescription g_APinDescription[] =
{
  // 0..6 - Digital pins
  // ----------------------
  { PORTA,  2, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_ANALOG), ADC_Channel0, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_2 },               // D1/DAC
  { PORTA,  6, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel6, PWM1_CH0, TCC1_CH0, EXTERNAL_INT_6 },         // D2/MOSI
  { PORTA,  5, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel5, PWM0_CH1, TCC0_CH1, EXTERNAL_INT_5 },         // D3/MISO
  { PORTA,  7, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel7, PWM1_CH1, TCC1_CH1, EXTERNAL_INT_7 },         // D4/SCK
  { PORTA,  0, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, TCC2_CH0, EXTERNAL_INT_0 },                                 // D5
  { PORTA,  1, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, TCC2_CH1, EXTERNAL_INT_1 },                                 // D6
  { PORTA,  4, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel4,PWM0_CH0,  TCC0_CH0, EXTERNAL_INT_4 },         // D7/VREFB

  // 7/8 - I2C
  // ----------------------
  { PORTA,  8, PIO_SERCOM_ALT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel16, PWM0_CH0, TCC0_CH0, EXTERNAL_INT_NMI }, // SDA/D0
  { PORTA,  9, PIO_SERCOM_ALT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel17, PWM0_CH1, TCC0_CH1, EXTERNAL_INT_9 },   // SCL/D2

  // 9..10 - SPI
  // --------------------
  { PORTA,  3, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_ANALOG), ADC_Channel1, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_3 },                                // D12
  { PORTA, 10, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel18, PWM1_CH0,  TCC1_CH0, EXTERNAL_INT_10},     // D13/LED

  // 11/12 - RX/TX
  // --------------------
  { PORTA, 23, PIO_SERCOM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM4_CH1, TC4_CH1, EXTERNAL_INT_7 },       // RX/D17
  { PORTA, 22, PIO_SERCOM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM4_CH0, TC4_CH0, EXTERNAL_INT_6 },       // TX/D16

  // 13-16 - Flash SPI
  // --------------------
  { PORTA, 16, PIO_SERCOM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM2_CH0, TCC2_CH0, EXTERNAL_INT_0 },      // Flash MOSI
  { PORTA, 17, PIO_SERCOM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM2_CH1, TCC2_CH1, EXTERNAL_INT_1 },      // Flash SCK
  { PORTA, 18, PIO_SERCOM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM3_CH0, TC3_CH0, EXTERNAL_INT_2 },       // Flash MISO
  { PORTA, 19, PIO_SERCOM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM3_CH1, TC3_CH1, EXTERNAL_INT_3 },       // Flash SS

  // 17/18 - SWD
  // --------------------
  { PORTA, 30, PIO_TIMER, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM1_CH0, TCC1_CH0, EXTERNAL_INT_10 },      // SWCLK/D22
  { PORTA, 31, PIO_TIMER, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM1_CH1, TCC1_CH1, EXTERNAL_INT_11 },      // SWDIO/D23

  // 19..21 - USB
  // --------------------
  { PORTA, 28, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE },                              // usb hOST Disable
  { PORTA, 24, PIO_COM, PIN_ATTR_NONE, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE },                                 // usb/dm
  { PORTA, 25, PIO_COM, PIN_ATTR_NONE, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE },                                 // usb/dp

  // 22..25 - Other Pins
  // ----------------------
  { PORTA, 11, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), ADC_Channel19, PWM1_CH1, TCC1_CH1, EXTERNAL_INT_11 },
  { PORTA, 14, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE },
  { PORTA, 15, PIO_DIGITAL, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM3_CH1, TC3_CH1, EXTERNAL_INT_15 },
  { PORTA, 27, PIO_DIGITAL, PIN_ATTR_DIGITAL, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE }

};

extern "C" {
    unsigned int PINCOUNT_fn() {
        return (sizeof(g_APinDescription) / sizeof(g_APinDescription[0]));
    }
}

const void* g_apTCInstances[TCC_INST_NUM+TC_INST_NUM]={ TCC0, TCC1, TCC2, TC3, TC4, TC5 } ;

// Multi-serial objects instantiation
SERCOM sercom0( SERCOM0 ) ;
SERCOM sercom1( SERCOM1 ) ;
SERCOM sercom2( SERCOM2 ) ;
SERCOM sercom3( SERCOM3 ) ;

Uart Serial( &sercom3, PIN_SERIAL_RX, PIN_SERIAL_TX, PAD_SERIAL_RX, PAD_SERIAL_TX ) ;

void SERCOM3_Handler()
{
  Serial.IrqHandler();
}

variant.h file as below

#ifndef _VARIANT_ARDUINO_ZERO_
#define _VARIANT_ARDUINO_ZERO_

// The definitions here needs a SAMD core >=1.6.6
#define ARDUINO_SAMD_VARIANT_COMPLIANCE 10606

/*----------------------------------------------------------------------------
 *        Definitions
 *----------------------------------------------------------------------------*/

/** Frequency of the board main oscillator */
#define VARIANT_MAINOSC		(32768ul)

/** Master clock frequency */
#define VARIANT_MCK			  (F_CPU)

/*----------------------------------------------------------------------------
 *        Headers
 *----------------------------------------------------------------------------*/

#include "WVariant.h"

#ifdef __cplusplus
#include "SERCOM.h"
#include "Uart.h"
#endif // __cplusplus

#ifdef __cplusplus
extern "C"
{
#endif // __cplusplus

/*----------------------------------------------------------------------------
 *        Pins
 *----------------------------------------------------------------------------*/

// Number of pins defined in PinDescription array
#ifdef __cplusplus
extern "C" unsigned int PINCOUNT_fn();
#endif
#define PINS_COUNT           (PINCOUNT_fn())
#define NUM_DIGITAL_PINS     (14u)
#define NUM_ANALOG_INPUTS    (0u)
#define NUM_ANALOG_OUTPUTS   (0u)
#define analogInputToDigitalPin(p)  ((p < 6u) ? (p) + 22u : -1)

#define digitalPinToPort(P)        ( &(PORT->Group[g_APinDescription[P].ulPort]) )
#define digitalPinToBitMask(P)     ( 1 << g_APinDescription[P].ulPin )
//#define analogInPinToBit(P)        ( )
#define portOutputRegister(port)   ( &(port->OUT.reg) )
#define portInputRegister(port)    ( &(port->IN.reg) )
#define portModeRegister(port)     ( &(port->DIR.reg) )
#define digitalPinHasPWM(P)        ( g_APinDescription[P].ulPWMChannel != NOT_ON_PWM || g_APinDescription[P].ulTCChannel != NOT_ON_TIMER )


// RX and TX LEDs are not present on the board.
 #define PIN_LED_13           (10u)

 #define PIN_LED              PIN_LED_13

/*
 * Serial interfaces
 */

// Serial
#define PIN_SERIAL_TX       (11ul)
#define PIN_SERIAL_RX       (12ul)
#define PAD_SERIAL_TX       (UART_TX_PAD_0)
#define PAD_SERIAL_RX       (SERCOM_RX_PAD_1)

/*
 * SPI Interfaces
 */
#define SPI_INTERFACES_COUNT 1

#define PIN_SPI_MOSI         (13u)
#define PIN_SPI_MISO         (14u)
#define PIN_SPI_SCK          (15u)
#define PIN_SPI_SS			     (16u)
#define PERIPH_SPI           sercom1
#define PAD_SPI_TX           SPI_PAD_0_SCK_1
#define PAD_SPI_RX           SERCOM_RX_PAD_2

static const uint8_t SS	  = PIN_SPI_SS ;
static const uint8_t MOSI = PIN_SPI_MOSI ;
static const uint8_t MISO = PIN_SPI_MISO ;
static const uint8_t SCK  = PIN_SPI_SCK ;

/*
 * Wire Interfaces
 */
//I2C/Qwiic Interface
#define WIRE_INTERFACES_COUNT 1

#define PIN_WIRE_SDA         (7u)
#define PIN_WIRE_SCL         (8u)
#define PERIPH_WIRE          sercom2
#define WIRE_IT_HANDLER      SERCOM2_Handler

static const uint8_t SDA = PIN_WIRE_SDA;
static const uint8_t SCL = PIN_WIRE_SCL;

/*
 * USB
 */
//#define PIN_USB_HOST_ENABLE (10ul)
#define PIN_USB_DM          (20ul)
#define PIN_USB_DP          (21ul)


#ifdef __cplusplus
}
#endif

/*----------------------------------------------------------------------------
 *        Arduino objects - C++ only
 *----------------------------------------------------------------------------*/

#ifdef __cplusplus

/*	=========================
 *	===== SERCOM DEFINITION
 *	=========================
*/
extern SERCOM sercom0;
extern SERCOM sercom1;
extern SERCOM sercom2;
extern SERCOM sercom3;


extern Uart Serial;


#endif

// These serial port names are intended to allow libraries and architecture-neutral
// sketches to automatically default to the correct port name for a particular type
// of use.  For example, a GPS module would normally connect to SERIAL_PORT_HARDWARE_OPEN,
// the first hardware serial port whose RX/TX pins are not dedicated to another use.
//
// SERIAL_PORT_MONITOR        Port which normally prints to the Arduino Serial Monitor
//
// SERIAL_PORT_USBVIRTUAL     Port which is USB virtual serial
//
// SERIAL_PORT_LINUXBRIDGE    Port which connects to a Linux system via Bridge library
//
// SERIAL_PORT_HARDWARE       Hardware serial port, physical RX & TX pins.
//
// SERIAL_PORT_HARDWARE_OPEN  Hardware serial ports which are open for use.  Their RX & TX
//                            pins are NOT connected to anything by default.
#define SERIAL_PORT_USBVIRTUAL      SerialUSB
#define SERIAL_PORT_MONITOR         SerialUSB
#define SERIAL_PORT_HARDWARE        Serial
#define SERIAL_PORT_HARDWARE_OPEN   Serial

#endif /* _VARIANT_ARDUINO_ZERO_ */

The Arduino sketch:

const int IV_EN = 15;
const int Modem_PWR_EN = 28;
const int ADC_PWR_EN = 30;
const int Sensor_PWR_EN = 31;

void setup() 
{

  //Initialise serial monitor
  SerialUSB.begin(9600); // Initialize Serial Monitor USB
  //Serial.begin(9600); // Initialize hardware serial port, pins 17/16

  while (!SerialUSB) ; // Wait for Serial monitor to open

  SerialUSB.println("Monitor");
  SerialUSB.print("Software Version ");
  SerialUSB.print(SW_Version/10);
  SerialUSB.print(".");
  SerialUSB.println(SW_Version%10);
  SerialUSB.println("");

  pinMode(IV_EN, OUTPUT);
  digitalWrite(IV_EN, LOW);

  pinMode(Sensor_PWR_EN, OUTPUT);
  digitalWrite(Sensor_PWR_EN, HIGH);

  pinMode(ADC_PWR_EN, OUTPUT);
  digitalWrite(ADC_PWR_EN, LOW);

//Crashes when I try to set this pin low
  pinMode(Modem_PWR_EN, OUTPUT);
  digitalWrite(Modem_PWR_EN, LOW);

void loop() 
{

}
2

I have absolutely no knowledge of the processor that you use. Have you tried a double tap on the reset button to activate the boot loader? If your custom board does not have a reset button, implement one in some way. If that works, you at least don't have to burn the boot loader every time.

So maybe show the software and not just part of it? That might help others to help you.

3

Yes, I have already decided to implement a push button in the next rev of the hardware if we are going ahead in the Arduino route.

The software that I shared is where I'm up to. It's very basic, just turning on some I/O and enabling Serial USB.

4

I have to apologise; I did miss the second code block with the actual code :frowning:

5

No worries.

I think the issue happens only when I try to control PA14 pin as digital IO while the serial USB is running. Just looking at a similar SAMD21 bootloader this pin is defined for VBUS detection. I have tried every way I can think of to come with a fix but no luck.

6

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