AVR Freaks

Oh. It needs to be in output mode? I completely missed that. However, I still am unable to control the leds on the expander board.

Modified the code a bit according to what I understood from the datasheet + Github along with your hint.

#include <atmel_start.h>

/*
Atmel START configs:
 SPI Master Sync:
  Pins[CS, SCK, MISO, MOSI]: PB3, PB13, PB0, PB1
  Speed: 500 kHz
  Character size: 8 bits
  Baud rate: 500 kHz
*/

 

#define IODIRA  (0x00)       // MCP23x17 I/O Direction Register
#define GPIOA   (0x12)       // MCP23x17 GPIO Port Register
#define OPCODEW (0b01000000) // Opcode for MCP23S17 with LSB (bit0) set to write (0), address OR'd in later, bits 1-3

 

static const uint16_t sleep_time = 100;

 

static void write_to_expander(const struct io_descriptor* io, const uint8_t reg, const uint8_t data)

{
    const uint8_t write_arr[3] = {OPCODEW, reg, data};
    io_write(io, write_arr, 3);
}

 

static struct io_descriptor* SPI_0_expander_example_init(void)
{
    struct io_descriptor *io;
    spi_m_sync_get_io_descriptor(&SPI_0, &io);

    spi_m_sync_enable(&SPI_0);

    write_to_expander(io, IODIRA, 0b00000000);
    write_to_expander(io, GPIOA, 0b00000000);

    return io;
}

 

int main(void)
{
    /* Initializes MCU, drivers and middleware */
    atmel_start_init();
    
    struct io_descriptor *io = SPI_0_expander_example_init();
    
    while (1) {
        // The write mode is sequential by default, so no need to address the pins
        io_write(io, 0b11111111, 1);
        delay_ms(10);
        io_write(io, 0b00000000, 1);
        delay_ms(10);
    }
}

This now hangs on the first io_write() in SPI_0_expander_example_init()'s write_to_expander().

From debugging, I noticed the program can't exit the loop in _spi_m_sync_trans() in Atmel START generated hpl_usart_spi_m_sync.c.

Does this mean SAME70 is unable to receive anything from the expander? In which case my soldering for the pins just could be bad.

EDIT: Checked the soldering and it seemed ok. Not sure why the program hangs in that loop then...

Thanks for the reply and pointing out the sequential mode.

I ended up checking the charts in the datasheet more than reading the text, coming to my own incorrect conclusion.

I'm now controlling the CS pin just as a normal GPIO pin and disabling the sequential write.

#include <atmel_start.h>

 

/*
Atmel START configs:
 SPI Master Sync:
  Pins[SCK, MISO, MOSI]: PB13, PB0, PB1
   CS pin(PB3) controlled manually as GPIO
  Speed: 500 kHz
  Character size: 8 bits
  Baud rate: 1 MHz
*/

 

#define IOCON   (0x0A)       // MCP23x17 Configuration Register
#define IODIRA  (0x00)       // MCP23x17 I/O Direction Register
#define GPIOA   (0x12)       // MCP23x17 GPIO Port Register
#define OPCODEW (0b01000000) // Opcode for MCP23S17 with LSB (bit0) set to write (0), address OR'd in later, bits 1-3
#define PB3 GPIO(GPIO_PORTB, 3)

 

static void write_to_expander(const struct io_descriptor* io, const uint8_t reg, const uint8_t data){
    const uint8_t write_arr[3] = {OPCODEW, reg, data};
    gpio_set_pin_level(PB3, false);
    io_write(io, write_arr, 3);
    gpio_set_pin_level(PB3, true);
}

 

static struct io_descriptor* SPI_0_expander_example_init(void)
{
    struct io_descriptor *io;
    spi_m_sync_get_io_descriptor(&SPI_0, &io);
    spi_m_sync_enable(&SPI_0);
    gpio_set_pin_direction(PB3, GPIO_DIRECTION_OUT);
    gpio_set_pin_level(PB3, true);
    write_to_expander(io, IOCON, 0b00100000);
    write_to_expander(io, IODIRA, 0b00000000);
    write_to_expander(io, GPIOA, 0b00000000);
    
    return io;
}

 

int main(void)
{
    /* Initializes MCU, drivers and middleware */
    atmel_start_init();
    
    struct io_descriptor *io = SPI_0_expander_example_init();
    
    while (1) {
        write_to_expander(io, GPIOA, 0b11001100);
        delay_ms(10);
        write_to_expander(io, GPIOA, 0b00110011);
        delay_ms(10);
    }
}

Some debugging: the program still seems to loop in the _spi_m_sync_transfer in file hpl_usart_spi_m_sync.c

• The _spi_m_sync_transfer loops as txcnt and rxcnt never increases after first byte sent
• _spi_tx_check_and_send and _spi_rx_check_and_receive return false constantly from rx/tx ready check

So after the first byte, the program never gets ready for the next read/write.

Just to make sure, as I'm choosing those pins (PB0, PB1, PB13) in Atmel START, the USART RX pin is always used as MOSI, TX pin as MISO and SCK as... well, SCK, right? The SAMA70 datasheet and the original pin functionalities point to that, but there's no clear mention of it in Atmel START. You can choose other pins too in Atmel START for USART SPI, I just don't know how could I even try to use them.