Edit: I solved the problem by changing the prescaler.
//ADC->ADC_MR |= 0x80; // free running, 1000 0000
ADC->ADC_MR |= 0x1480; // prescal, 20 + free running
Hello everyone,
I tried the code from Arduino Due: ADC → DMA → USB @ 1MSPS · GitHub for sampling a 100 Hz sine wave, slightly altered version is given below. However, I get corrupt data as shown below. I searched for solutions and changed a few things, but it only gets worse. Can you suggest anything?
The image is attached.
#undef HID_ENABLED
// Arduino DUE ADC->DMA->USB 1MSPS
// Input: Analog in A0
// Output: Raw stream of uint15_t in range 0-4095 on Native SerialUSB/ACM
unsigned long sampleSize, st, et;
volatile int bufn, obufn;
uint16_t buf[4][256]; // 4 buffers of 256 readings
void ADC_Handler() {
int f = ADC->ADC_ISR;
if (f & (1 << 27)) {
bufn = (bufn + 1) & 3;
ADC->ADC_RNPR = (uint32_t)buf[(bufn + 1) & 3];
ADC->ADC_RNCR = 256;
}
}
void setup() {
pinMode(LED_BUILTIN, OUTPUT);
SerialUSB.begin(0);
pmc_enable_periph_clk(ID_ADC);
adc_init(ADC, SystemCoreClock, ADC_FREQ_MAX, ADC_STARTUP_FAST);
ADC->ADC_MR |= 0x80; // free running, 1000 0000
ADC->ADC_CHER = 0x80; // enable ch's
NVIC_EnableIRQ(ADC_IRQn);
ADC->ADC_IDR = ~(1 << 27);
ADC->ADC_IER = 1 << 27;
//ADC->ADC_EMR = 0x01000000;
ADC->ADC_RPR = (uint32_t)buf[0]; // DMA buffer
ADC->ADC_RCR = 256;
ADC->ADC_RNPR = (uint32_t)buf[1]; // next DMA buffer
ADC->ADC_RNCR = 256;
bufn = 1;
obufn = 0;
ADC->ADC_PTCR = 1;
ADC->ADC_CR = 2;
}
void loop() {
while (!SerialUSB.available()) {
digitalWrite(LED_BUILTIN, HIGH); delay(25);
digitalWrite(LED_BUILTIN, LOW); delay(225);
}
sampleSize = SerialUSB.parseInt();
if (sampleSize > 1) {
st = micros();
for (int i = 0; i < sampleSize; i++) {
while ((obufn + 1) % 4 == bufn); // wait for buffer to be full
//SerialUSB.print(obufn); SerialUSB.print(" "); SerialUSB.println(bufn);
SerialUSB.write((uint8_t *)buf[obufn], 512); // send it - 512 bytes = 256 uint16_t
obufn = (obufn + 1) & 3;
}
et = micros();
SerialUSB.println();
SerialUSB.println("#");
SerialUSB.println(et - st);
SerialUSB.print( (sampleSize * 256 * 1000.0) / (et - st)); SerialUSB.println(" kHz");
}
sampleSize = 0;
}
