D21G/PROTO: DAC0 analog output voltage reaches saturation at a count of 71% with about 2.3V (never reaching full range)

1. may be default/unchanged AREF seems not to be 3V3, but 2V23?
2. I can frequently change voltage (in my example in steps of +/-30 of 0..4095) down to 0V out
3. but reaching an integer of about 3000 (2977 to 3007) the output reaches about 2.29V (DVM reading) and gets stuck, will never increase more
4. by decrementing below that, the output continues to follow to 0V out
5. Independant from the set up AREF I would expect the output to follow 0..4095 more or less uniformly linear?
6. setting analogWriteResolution(8) - the output stops at about 187 (also reading 2.29V)
7. setting to 10(bit) - the saturation level of 2.27V is reached at int 735
8. the limit is close to 71% (sqrt of 1/2 ?) - but AC reading is zero, so this should be solid DC (not PWM or s.th. else?)
9. starting with a integer of "max/2" (50%) I get always a 1.578V (1.57..1.58 in 20V) reading which is close to 3.32V/2?
10. setting different analogReference(AR_...) seems not to work at all, got same 50% reading of 1.57V at startup
11. (Remark: the DVM reading is naturally poor due to the lowest part of the 20V-range (200mV/2V/20V/...), so the real value could be much different, but never ever like 3V3 - the saturation is seen clearly)

Do I need different steps or do I have to change to another order of commands to set up this test?

```
// started with
  const int vout_max = 4095;
  int vout = vout_max / 2;  // to start with
  pinMode(DAC0, OUTPUT); //D18
  analogWriteResolution(12);
  analogReference(AR_DEFAULT); // = Vcc 3V3
  analogWrite(DAC0, vout);
... // and later
 if( !digitalRead(buttonUpPin)) {
    vout += 30;
    if (vout > vout_max) vout = vout_max;
    analogWrite(DAC0, vout);
    SerialUSB.print("vout = "); SerialUSB.println(vout);
  } else if ...

```

? a #D21G and #DAC(0) or #analogWrite label would help?

PROTO

• Comment
• Close
• Edit
• Delete

kgSW

kgSW

14

| 0 0 0

Asked on 12/13/21, 12:51 AM

0

vote

1264 Views