CODEWITHSUNDEEP
cspilpc
Arrrow
Arrrow

Reputation: 542

SPI peripheral on LPC1769

I need to send certain data to an FPGA with SPI using my LPC1769. However I don't quite understand how I should approach this. I currently have this code which ends up in the hardfault handler. I'm not allowed to use CMSIS so I had to define the registers myself.

void sendData(uint8_t *buf, uint32_t Length) {
    uint32_t i;
    for (i = 0; i < Length; i++) {
        while (S0SPSR != (1 << 7)) {
            S0SPDR = *buf;
            gpio0WritePin(15, 1);
            gpio0WritePin(15, 0);
            buf++;
        }
    }
return;
}

and my main function:

uint8_t TX[16];
int main(void) {
    SpiInit();
    TX[0] = 0x48;
    TX[1] = 0x65;
    TX[2] = 0x6c;
    TX[3] = 0x6c;
    TX[4] = 0x6f;
    while (1) {
        SPI_Begin();
        sendData((uint8_t*)TX, 5);
        SPI_End();
    }
 }

Upvotes: 0

Views: 1019

Answers (1)

xbug
xbug

Reputation: 1472

You definitely don't want to go bit-banging data to the SPI bus like that with this kind on modern microcontrollers.

If for some reason you're not allowed to use CMSIS, I would suggest that you have a look at how CMSIS does SPI communication. Open this (or better yet: print it out), and use "Chapter 17: LPC176x/5x SPI" from the LPC176x/5x User Manual as a reference as you go along (pages 410-420). The code should be reasonably easy to follow.

In a nutshell, you need to:

  • enable the SPI controller through the Power Control for Peripherals Register,
  • setup and enable the clock for this peripheral (Perpheral Clock Selection Register),
  • configure the I/O pins associated to SPI (MOSI, MISO, CLK, CS), clock polarity, etc... through the SPI Control Register,
  • setup interrupts so you don't have to waste time looping around status registers while waiting for new data to come in,
  • read and write data 8 bit at a time using the SPI Data Register.

Don't forget to use interrupts, your CPU cycles are best used crunching data than anything else (especially polling status registers, a very common mistake unfortunately).

Upvotes: 1

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