I modified the analogDifferentialRead example to test setting the gain values of the programmable gain amplifiers (PGAs) for ADC0 and ADC1. Changing the gain to ADC0 works as I expected but whenever I change the gain to ADC1 the ADC0 gain changes also. Here's the test case:
Here is a sample output with annotations:
Any thoughts on what's going on here?
Code:
/* Test for analogReadDifferentialGain as modified from analogReadDifferential
* You can interactively change PGA gain values from the Serial Monitor:
* Enter two characters: cg
* where c selects the ADC number and can be 0 or 1
* and where g sets the gain and can be 0, 1, 2, 3, 4, 5, or 6
* for a gain value of 1, 2, 4, 8, 16, 32, or 64 respectively
* You can enter strings of commands. For example 000102 will set ADC0's gain to
* 1, 2, and 4 on successive iterations. 1302 will set AGC1's gain to 8 and
* AGC0's gain to 4.
*
* ADC0 and the corresponding PGA0 are connected to pins A10/A11 (+/-)
* ADC1 and the corresponding PGA1 are connected to pins A12/A13 (+/-)
* On the breadboard A11 and A13 are tied to ground. A10 and A12 are tied to
* the same pot and that is adjusted to about 0.1 volts.
*/
#include <ADC.h>
ADC *adc = new ADC(); // adc object
void setup() {
pinMode(LED_BUILTIN, OUTPUT);
pinMode(A10, INPUT); //Diff Channel 0 Positive
pinMode(A11, INPUT); //Diff Channel 0 Negative
pinMode(A12, INPUT); //Diff Channel 3 Positive
pinMode(A13, INPUT); //Diff Channel 3 Negative
Serial.begin(9600);
///// ADC0 ////
adc->setAveraging(8); // set number of averages
adc->setResolution(9); // set bits of resolution
// these can be ADC_VERY_LOW_SPEED, ADC_LOW_SPEED, ADC_MED_SPEED,
// ADC_HIGH_SPEED_16BITS, ADC_HIGH_SPEED or ADC_VERY_HIGH_SPEED
adc->setConversionSpeed(ADC_MED_SPEED); // change the conversion speed
adc->setSamplingSpeed(ADC_MED_SPEED); // change the sampling speed
// always call the compare functions after changing the resolution!
adc->disableCompare(ADC_0);
////// ADC1 /////
adc->setAveraging(8, ADC_1); // set number of averages
adc->setResolution(9, ADC_1); // set bits of resolution
adc->setConversionSpeed(ADC_MED_SPEED, ADC_1); // change the conversion speed
adc->setSamplingSpeed(ADC_MED_SPEED, ADC_1); // change the sampling speed
// always call the compare functions after changing the resolution!
adc->disableCompare(ADC_1);
adc->enablePGA(1, ADC_0); // gain can be 1,2,4,8,16,32,64
adc->enablePGA(1, ADC_1);
delay(500);
}
int value[2];
int c = 0, g = 0;
float k[] = {0, 0};
void loop() {
if (Serial.available()) {
c = Serial.read() - '0'; // get DAC number
g = Serial.read() - '0'; // get gain value
Serial.println("");
Serial.print("Cmd: "); Serial.print(c); Serial.print(g);
Serial.print(" (adc->enablePGA(1<<"); Serial.print(g); Serial.print(", ");
Serial.print(c); Serial.println(");)");
adc->enablePGA(1<<g, c); // set gain
for (c=0; c<2; c++) {
Serial.print(" ADC"); Serial.print(c);
Serial.print(" MaxVal: "); Serial.print(adc->getMaxValue(c));
Serial.print(" PGA: "); Serial.print(adc->getPGA(c));
k[c] = 3.3/adc->getPGA(c)/adc->getMaxValue(c);
Serial.print(" k: "); Serial.println(k[c], 6);
}
}
value[0] = adc->analogReadDifferential(A10, A11, ADC_0);
value[1] = adc->analogReadDifferential(A12, A13, ADC_1);
for (c=0; c<2; c++) {
Serial.print("ADC"); Serial.print(c);
Serial.print(" Value: (0x"); Serial.print(value[c], HEX);
Serial.print(", Voltage: "); Serial.print(k[c]*value[c], 3);
Serial.print(") ");
}
Serial.println("");
if(adc->adc0->fail_flag) {
Serial.print("ADC0 error flags: 0x");
Serial.println(adc->adc0->fail_flag, HEX);
}
if(adc->adc1->fail_flag) {
Serial.print("ADC1 error flags: 0x");
Serial.println(adc->adc1->fail_flag, HEX);
}
digitalWriteFast(LED_BUILTIN, !digitalReadFast(LED_BUILTIN));
delay(1000);
}Cmd: 01 (adc->enablePGA(1<<1, 0)
ADC0 MaxVal: 255 PGA: 2 k: 0.006471
ADC1 MaxVal: 255 PGA: 1 k: 0.012941
ADC0 Value: (0x10, Voltage: 0.104) ADC1 Value: (0x8, Voltage: 0.104)
This is as expected. PGA0 is set to 2x gain. PGA1 is unchanged.
Cmd: 02 (adc->enablePGA(1<<2, 0)
ADC0 MaxVal: 255 PGA: 4 k: 0.003235
ADC1 MaxVal: 255 PGA: 1 k: 0.012941
ADC0 Value: (0x1F, Voltage: 0.100) ADC1 Value: (0x8, Voltage: 0.104)
This is as expected. PGA0 is set to 4x gain. PGA1 is unchanged.
Cmd: 00 (adc->enablePGA(1<<0, 0)
ADC0 MaxVal: 255 PGA: 1 k: 0.012941
ADC1 MaxVal: 255 PGA: 1 k: 0.012941
ADC0 Value: (0x8, Voltage: 0.104) ADC1 Value: (0x8, Voltage: 0.104)
This is as expected. PGA0 is set to 1x gain.
Cmd: 14 (adc->enablePGA(1<<4, 1)
ADC0 MaxVal: 255 PGA: 16 k: 0.000809
ADC1 MaxVal: 255 PGA: 16 k: 0.000809
ADC0 Value: (0x76, Voltage: 0.095) ADC1 Value: (0x75, Voltage: 0.095)
This is wrong. PGA1 is set to 16x gain and PGA0 changes also.
Cmd: 15 (adc->enablePGA(1<<5, 1)
ADC0 MaxVal: 255 PGA: 32 k: 0.000404
ADC1 MaxVal: 255 PGA: 32 k: 0.000404
ADC0 Value: (0xDD, Voltage: 0.089) ADC1 Value: (0xDC, Voltage: 0.089)
This is wrong. PGA1 is set to 32x gain and PGA0 changes also.
Cmd: 10 (adc->enablePGA(1<<0, 1)
ADC0 MaxVal: 255 PGA: 1 k: 0.012941
ADC1 MaxVal: 255 PGA: 1 k: 0.012941
ADC0 Value: (0x8, Voltage: 0.104) ADC1 Value: (0x8, Voltage: 0.104)
This is wrong. PGA1 is set to 1x gain and PGA0 changes also.
Any thoughts on what's going on here?