upduino_spi.cpp

// Send 8 bit data to FPGA on Upduino via SPI
// See https://jpfau.org/blog/upduino-usb-spi/ for details and FPGA sample application.
// compile like this: g++ upduino_spi.cpp -o upduino_spi -lftdi1 `pkg-config libftdi1 --cflags`
#include <ftdi.h>
#include <unistd.h>
#include <stdexcept>
#include <string.h>

using std::string;

#define VENDOR 0x0403
#define PRODUCT 0x6014

// ADBUS0
#define PIN_SCK 0 
// ADBUS1
#define PIN_MOSI 1 
// ADBUS2
#define PIN_NSS 2

#define OUTPUT_PINMASK ((1 << PIN_SCK) | (1 << PIN_MOSI) | (1 << PIN_NSS))

void enforce(bool condition, string msg = "Enforcement failed")
{
    if (!condition)
        throw std::runtime_error(msg);
}

class SPIDriver
{
private:
    struct ftdi_context _ftdi;

    void setupMPSSE()
    {
        // 1 MHz, Disable adaptive and 3 phase clocking, set ADBUS all spi pins as output, nSS initial high
        uint8_t buf[] = {TCK_DIVISOR, 0x05, 0x00,
            DIS_ADAPTIVE,
            DIS_3_PHASE,
            SET_BITS_LOW, (1 << PIN_NSS), OUTPUT_PINMASK
        };

        // Write the setup to the chip.
        enforce(ftdi_write_data(&_ftdi, buf, sizeof(buf)) == sizeof(buf), "FTDI setup failed");
    }

public:
    SPIDriver() {}

    void open()
    {
        auto status = ftdi_init(&_ftdi);
        enforce(status == 0, "Failed to initialize libftdi");
        status = ftdi_usb_open(&_ftdi, VENDOR, PRODUCT);
        enforce(status == 0, "Failed to open device: " + string(ftdi_get_error_string(&_ftdi)));

        enforce(ftdi_usb_reset(&_ftdi) == 0, "ftdi_usb_reset failed");
        enforce(ftdi_set_interface(&_ftdi, INTERFACE_ANY) == 0, "ftdi_set_interface failed");
        enforce(ftdi_set_bitmode(&_ftdi, 0, 0) == 0, "ftdi_set_bitmode failed");
        enforce(ftdi_set_bitmode(&_ftdi, 0, BITMODE_MPSSE) == 0, "ftdi_set_bitmode failed");
        enforce(ftdi_tcioflush(&_ftdi) == 0, "ftdi_tcioflush failed");
        usleep(50000);

        setupMPSSE();
    }

    void writeData(uint8_t data)
    {
        uint8_t buf[] = {
            SET_BITS_LOW, 0x00, OUTPUT_PINMASK,
            MPSSE_DO_WRITE | MPSSE_WRITE_NEG | MPSSE_LSB, 0x00, 0x00, data,
            SET_BITS_LOW, (1 << PIN_NSS), OUTPUT_PINMASK
        };
        enforce(ftdi_write_data(&_ftdi, buf, sizeof(buf)) == sizeof(buf), "FTDI write failed");
    }

    void close()
    {
        ftdi_usb_reset(&_ftdi);
        enforce(ftdi_usb_close(&_ftdi) == 0, "ftdi_usb_close failed");
    }
};

#include <stdio.h>

int main(int argc, char* argv[])
{
    if (argc != 9)
    {
        printf("Usage: upduino_spi 0 0 0 0 0 0 0\n");
        return -1;
    }
    
    uint8_t data = 0;
    for (size_t i = 0; i < 8; i++)
    {
        if (string(argv[1+i]) == "1")
            data |= (1 << (7 - i));
    }

    auto dev = new SPIDriver();
    dev->open();
    dev->writeData(data);
    dev->close();
    return 0;
}