I'm trying to make i2s working on mbed os by using NRF52 development kit board (based on nrf52832).
Looks like I'm missing something. What I managed to do so far is:
#include "mbed.h"
#include "nrf52.h"
#include <nrf_i2s.h>
int main(){
Serial pc(USBTX, USBRX);
const int frequency = 440; // frequency of square wave in Hz
const int amplitude = 500; // amplitude of square wave
const int sampleRate = 8000; // sample rate in Hz
const int halfWavelength = (sampleRate / frequency); // half wavelength of square wave
uint32_t sample = amplitude; // current sample value
int count = 0;
NRF_I2S_Type * p_i2s;
nrf_i2s_enable(p_i2s);
nrf_i2s_pins_set(p_i2s, 11, 12, NRF_I2S_PIN_NOT_CONNECTED, 13, NRF_I2S_PIN_NOT_CONNECTED);
bool ret = nrf_i2s_configure(p_i2s, NRF_I2S_MODE_MASTER, NRF_I2S_FORMAT_I2S, NRF_I2S_ALIGN_LEFT, NRF_I2S_SWIDTH_24BIT, NRF_I2S_CHANNELS_STER
EO, NRF_I2S_MCK_DISABLED, NRF_I2S_RATIO_128X);
if (ret){
pc.printf("Success\n");
} else {
pc.printf("Error \n");
}
while(1){
if (count % halfWavelength == 0) {
// invert the sample every half wavelength count multiple to generate square wave
sample = -1 * sample;
}
// write the same sample twice, once for left and once for the right channel
nrf_i2s_tx_buffer_set(p_i2s, &sample);
nrf_i2s_tx_buffer_set(p_i2s, &sample);
// increment the counter for the next sample
count++;
}
return 0;
}
But it's not working. Not to mention the warning that p_i2s is not initialised.
