//polls for the end of an adc conversion event. Then processe buffer to extract the averaged
//value. It takes this value and averages it with the existing value in an 8 position buffer
//which serves as a super fast place for other code to retrieve ADC values
// This is only used when RAWADC is not defined
void sys_io_adc_poll() {
if (obufn != bufn) {
uint32_t tempbuff[8] = {0,0,0,0,0,0,0,0}; //make sure its zero'd
//the eight or four enabled adcs are interleaved in the buffer
//this is a somewhat unrolled for loop with no incrementer. it's odd but it works
for (int i = 0; i < 256;) {
tempbuff[3] += adc_buf[obufn][i++];
tempbuff[2] += adc_buf[obufn][i++];
tempbuff[1] += adc_buf[obufn][i++];
tempbuff[0] += adc_buf[obufn][i++];
}
//now, all of the ADC values are summed over 32/64 readings. So, divide by 32/64 (shift by 5/6) to get the average
//then add that to the old value we had stored and divide by two to average those. Lots of averaging going on.
for (int j = 0; j < 4; j++) {
adc_values[j] += (tempbuff[j] >> 6);
adc_values[j] = adc_values[j] >> 1;
}
for (int i = 0; i < NUM_ANALOG; i++) {
int val;
val = getRawADC(i);
// addNewADCVal(i, val);
// adc_out_vals[i] = getADCAvg(i);
adc_out_vals[i] = val;
}
obufn = bufn;
}
/* Poll the ADC for altitude values and put the
* latest values on the altitude queue.
*/
static void vGetAltitude(void *pvParameters) {
unsigned int groundValue = getRawADC();
unsigned int maxValue = groundValue - 270;
unsigned int rawADCvalue;
float altitude;
xQueueHandle xOLEDQueue = ( xQueueHandle ) pvParameters;
portTickType xLastWakeTime = xTaskGetTickCount();
/* Define a period of 2 milliseconds (500Hz) */
const portTickType xPeriod = ( 3 / portTICK_RATE_MS );
for ( ;; ) {
vTaskDelayUntil( &xLastWakeTime, xPeriod );
rawADCvalue = getRawADC();
//Dynamically adjust the ground voltage value (differs on each helicopter).
if (rawADCvalue > groundValue) {
groundValue = rawADCvalue;
}
//Dynamically adjust the max altitude voltage value.
if (rawADCvalue < (groundValue - 320)) {
rawADCvalue = maxValue;
}
//Convert the voltage values to a percentage of the total height.
altitude = 100.0f * (groundValue - rawADCvalue) / (groundValue - maxValue);
/* Uncomment to send the current altitude to the OLED */
//xQueueMessage message = { CURRENT_ALTITUDE, altitude };
//xQueueSendToBack( xOLEDQueue, &message, 0 );
xAltMessage altMessage = { altitude };
xQueueSendToBack( xAltQueue, &altMessage, 0 );
}
}