4 years, 8 months ago.

Hello Mark,

The code provided in the spi_api.c file is specific for the given target so it won't work with other chips. It represents the hardware abstraction layer (HAL) and those C functions are not designed to be called directly from the application program but rather from Mbed's SPI or SPISlave class methods. But that's already done by Mbed. This way Mbed's SPI Master API and SPI Slave API could be same for any target supported by Mbed. The only target specific things in an application program are SPI pin names.

For example, in your case the SPI Master test program for the STM target could look like:

#include "mbed.h"

SPI     spiMaster(SPI_MOSI, SPI_MISO, SPI_SCK, SPI_CS); // mosi, miso, sck, ssel pins
Serial  pc(USBTX, USBRX);                               // tx, rx pins

int main()
{
    int dataToSend = 0;
    int dataReceived;

    pc.printf("SPI Master\r\n");
    spiMaster.format(8, 3);       // Both, Master and Slave have to use the same format
    spiMaster.frequency(1000000); // and same frequency

    while (1) {
        dataReceived = spiMaster.write(dataToSend);
        pc.printf("Sent:%d \t\t\t Received:%d\r\n", dataToSend, dataReceived);
        dataToSend++;
        wait(5);
    }
}

and the SPI Slave test program for the nrf52811:

#include "mbed.h"

SPISlave    spiSlave(SPI_MOSI, SPI_MISO, SPI_SCK, SPI_CS);  // mosi, miso, sck, ssel pins
Serial      pc(USBTX, USBRX);                               // tx, rx pins

int main()
{
    int dataToSend = 0;
    int dataReceived;

    pc.printf("SPI Slave\r\n");
    spiSlave.format(8, 3);       // Both, Master and Slave have to use the same format
    spiSlave.frequency(1000000); // and same frequency
    while (1) {
        if (spiSlave.receive()) {
            spiSlave.reply(dataToSend);     // pre-load SPI with next reply data
            dataReceived = spiSlave.read(); // receive data from Master + send reply data back to Master
            pc.printf("Sent:%d /t/t/t Received:%d\r\n", dataToSend, dataReceived);
            dataToSend++;
        }
    }
}

Substitute the pin names in the codes above with those used on your custom board and compile the SPI Master for the STM target and the SPI Slave for the Nordic chip. Mbed will automatically take care that the correct spi_api.c file is used for the given target. Make sure that Master's MOSI pin is connected to Slave's MISO pin and Master's MISO pin to Slave's MOSI pin. The SSEL pins have to be connect one another. The SCK pins shall be connected to each other too.

That will make the build system aware of additional directories it must scan for BLE resources when compiling for the given target. Please read here for more details.