I quickly adapted Rick’s demo project to create some raw PCM file on SD
code
#include "Particle.h"
// Tested with Adafruit 1713
// Electret Microphone Amplifier - MAX9814 with Auto Gain Control
// https://www.adafruit.com/products/1713
//
// AR - No connection
// Out - Audio out (analog) to Photon A0
// Gain - No connection
// VDD - 3V3
// GND - GND
//
// ADCDMA - Class to use Photon ADC in DMA Mode
//
#include "adc_hal.h"
#include "gpio_hal.h"
#include "pinmap_hal.h"
#include "pinmap_impl.h"
#include <SdFat.h>
SdFat sd;
File myFile;
int fileCount = 0;
void buttonHandler(system_event_t event, int data); // forward declaration
const size_t SAMPLE_BUF_SIZE = 2048;
const int SAMPLE_PIN = A0;
const int SPI_CS = A2;
const long SAMPLE_RATE = 44100;
const unsigned long MAX_RECORDING_LENGTH_MS = 10000;
uint16_t samples[SAMPLE_BUF_SIZE];
unsigned long recordingStart;
enum State { STATE_WAITING, STATE_CONNECT, STATE_RUNNING, STATE_FINISH };
State state = STATE_WAITING;
//
//
//
class ADCDMA {
public:
ADCDMA(int pin, uint16_t *buf, size_t bufSize);
virtual ~ADCDMA();
void start(size_t freqHZ);
void stop();
private:
int pin;
uint16_t *buf;
size_t bufSize;
};
// Helpful post:
// https://my.st.com/public/STe2ecommunities/mcu/Lists/cortex_mx_stm32/Flat.aspx?RootFolder=https%3a%2f%2fmy%2est%2ecom%2fpublic%2fSTe2ecommunities%2fmcu%2fLists%2fcortex%5fmx%5fstm32%2fstm32f207%20ADC%2bTIMER%2bDMA%20%20Poor%20Peripheral%20Library%20Examples&FolderCTID=0x01200200770978C69A1141439FE559EB459D7580009C4E14902C3CDE46A77F0FFD06506F5B¤tviews=6249
ADCDMA::ADCDMA(int pin, uint16_t *buf, size_t bufSize) : pin(pin), buf(buf), bufSize(bufSize) {
}
ADCDMA::~ADCDMA() {
}
void ADCDMA::start(size_t freqHZ) {
// Using Dual ADC Regular Simultaneous DMA Mode 1
// Using Timer3. To change timers, make sure you edit all of:
// RCC_APB1Periph_TIM3, TIM3, ADC_ExternalTrigConv_T3_TRGO
RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA2, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE);
RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC2, ENABLE);
RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM3, ENABLE);
// Set the pin as analog input
// GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AN;
// GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
HAL_Pin_Mode(pin, AN_INPUT);
// Enable the DMA Stream IRQ Channel
NVIC_InitTypeDef NVIC_InitStructure;
NVIC_InitStructure.NVIC_IRQChannel = DMA2_Stream0_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);
// 60000000UL = 60 MHz Timer Clock = HCLK / 2
// Even low audio rates like 8000 Hz will fit in a 16-bit counter with no prescaler (period = 7500)
TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
TIM_TimeBaseStructInit(&TIM_TimeBaseStructure);
TIM_TimeBaseStructure.TIM_Period = (60000000UL / freqHZ) - 1;
TIM_TimeBaseStructure.TIM_Prescaler = 0;
TIM_TimeBaseStructure.TIM_ClockDivision = 0;
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;
TIM_TimeBaseInit(TIM3, &TIM_TimeBaseStructure);
TIM_SelectOutputTrigger(TIM3, TIM_TRGOSource_Update); // ADC_ExternalTrigConv_T3_TRGO
TIM_Cmd(TIM3, ENABLE);
ADC_CommonInitTypeDef ADC_CommonInitStructure;
ADC_InitTypeDef ADC_InitStructure;
DMA_InitTypeDef DMA_InitStructure;
// DMA2 Stream0 channel0 configuration
DMA_InitStructure.DMA_Channel = DMA_Channel_0;
DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)buf;
DMA_InitStructure.DMA_PeripheralBaseAddr = 0x40012308; // CDR_ADDRESS; Packed ADC1, ADC2;
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralToMemory;
DMA_InitStructure.DMA_BufferSize = bufSize;
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_HalfWord;
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_HalfWord;
DMA_InitStructure.DMA_Mode = DMA_Mode_Circular;
DMA_InitStructure.DMA_Priority = DMA_Priority_High;
DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Enable;
DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
DMA_Init(DMA2_Stream0, &DMA_InitStructure);
// Don't enable DMA Stream Half / Transfer Complete interrupt
// Since we want to write out of loop anyway, there's no real advantage to using the interrupt, and as
// far as I can tell, you can't set the interrupt handler for DMA2_Stream0 without modifying
// system firmware because there's no built-in handler for it.
// DMA_ITConfig(DMA2_Stream0, DMA_IT_TC | DMA_IT_HT, ENABLE);
DMA_Cmd(DMA2_Stream0, ENABLE);
// ADC Common Init
ADC_CommonInitStructure.ADC_Mode = ADC_DualMode_RegSimult;
ADC_CommonInitStructure.ADC_Prescaler = ADC_Prescaler_Div2;
ADC_CommonInitStructure.ADC_DMAAccessMode = ADC_DMAAccessMode_1;
ADC_CommonInitStructure.ADC_TwoSamplingDelay = ADC_TwoSamplingDelay_5Cycles;
ADC_CommonInit(&ADC_CommonInitStructure);
// ADC1 configuration
ADC_InitStructure.ADC_Resolution = ADC_Resolution_12b;
ADC_InitStructure.ADC_ScanConvMode = DISABLE;
ADC_InitStructure.ADC_ContinuousConvMode = DISABLE;
ADC_InitStructure.ADC_ExternalTrigConvEdge = ADC_ExternalTrigConvEdge_Rising;
ADC_InitStructure.ADC_ExternalTrigConv = ADC_ExternalTrigConv_T3_TRGO;
ADC_InitStructure.ADC_DataAlign = ADC_DataAlign_Left;
ADC_InitStructure.ADC_NbrOfConversion = 1;
ADC_Init(ADC1, &ADC_InitStructure);
// ADC2 configuration - same
ADC_Init(ADC2, &ADC_InitStructure);
//
ADC_RegularChannelConfig(ADC1, PIN_MAP[pin].adc_channel, 1, ADC_SampleTime_15Cycles);
ADC_RegularChannelConfig(ADC2, PIN_MAP[pin].adc_channel, 1, ADC_SampleTime_15Cycles);
// Enable DMA request after last transfer (Multi-ADC mode)
ADC_MultiModeDMARequestAfterLastTransferCmd(ENABLE);
// Enable ADCs
ADC_Cmd(ADC1, ENABLE);
ADC_Cmd(ADC2, ENABLE);
ADC_SoftwareStartConv(ADC1);
}
void ADCDMA::stop() {
// Stop the ADC
ADC_Cmd(ADC1, DISABLE);
ADC_Cmd(ADC2, DISABLE);
DMA_Cmd(DMA2_Stream0, DISABLE);
// Stop the timer
TIM_Cmd(TIM3, DISABLE);
}
ADCDMA adcDMA(SAMPLE_PIN, samples, SAMPLE_BUF_SIZE);
void setup() {
Serial.begin(9600);
// Register handler to handle clicking on the SETUP button
System.on(button_click, buttonHandler);
pinMode(D7, OUTPUT);
if (sd.begin(SPI_CS, SPI_FULL_SPEED))
Serial.println("SD initialised");
else
Serial.println("failed to open card");
}
void loop() {
uint16_t *sendBuf = NULL;
switch(state) {
case STATE_WAITING:
// Waiting for the user to press the SETUP button. The setup button handler
// will bump the state into STATE_CONNECT
break;
case STATE_CONNECT:
{
char fileName[128];
snprintf(fileName, sizeof(fileName), "rec%04d.pcm", fileCount+1);
if (myFile.open(fileName, O_RDWR | O_CREAT | O_TRUNC)) {
fileCount++;
digitalWrite(D7, HIGH);
Serial.printlnf("Writing to %s", fileName);
recordingStart = millis();
adcDMA.start(SAMPLE_RATE);
state = STATE_RUNNING;
}
else {
Serial.printlnf("opening %s for write failed", fileName);
state = STATE_WAITING;
}
}
break;
case STATE_RUNNING:
if (DMA_GetFlagStatus(DMA2_Stream0, DMA_FLAG_HTIF0)) {
DMA_ClearFlag(DMA2_Stream0, DMA_FLAG_HTIF0);
sendBuf = &samples[0];
}
if (DMA_GetFlagStatus(DMA2_Stream0, DMA_FLAG_TCIF0)) {
DMA_ClearFlag(DMA2_Stream0, DMA_FLAG_TCIF0);
sendBuf = &samples[SAMPLE_BUF_SIZE / 2];
}
if (sendBuf != NULL) {
// There is a sample buffer to send
// Average the pairs of samples and adjust to 16bit signed PCM
for(size_t ii = 0, jj = 0; ii < SAMPLE_BUF_SIZE / 2; ii += 2, jj++) {
int32_t sum = sendBuf[ii] + sendBuf[ii + 1];
sendBuf[jj] = (int16_t)((sum / 2) - 32768);
}
int count = myFile.write((uint8_t *)sendBuf, SAMPLE_BUF_SIZE / 2);
if (count == SAMPLE_BUF_SIZE / 2) {
// Success
// Serial.printlnf("%d samples written", count);
}
else {
// Error
Serial.printlnf("error writing %d", count);
state = STATE_FINISH;
}
}
if (millis() - recordingStart >= MAX_RECORDING_LENGTH_MS) {
state = STATE_FINISH;
}
break;
case STATE_FINISH:
digitalWrite(D7, LOW);
adcDMA.stop();
Serial.println("stopping");
myFile.close();
state = STATE_WAITING;
break;
}
}
// button handler for the SETUP button, used to toggle recording on and off
void buttonHandler(system_event_t event, int data) {
switch(state) {
case STATE_WAITING:
state = STATE_CONNECT;
break;
case STATE_RUNNING:
state = STATE_FINISH;
break;
}
}