PSoC 5 - Found Possible problem in the Timer API when interacting with SAR ADC voltage reference VDD/2. | Cypress Semiconductor
PSoC 5 - Found Possible problem in the Timer API when interacting with SAR ADC voltage reference VDD/2.
I have found a problem that I isolated to being an iteration between the timer start / stop and de SAR ADC internal bypassed voltage reference, voltage VDD/2.
It shows a slow start that is very similar the curve charge of a capacitor, in what appears to be a reinitialization of the voltage reference and it’s bypass capacitor.
I used the kit 059 for this example.
I send my code that demonstrates de problem, the ADC/MUX pin has to be feed with an input that has an dc offset off 2.5 Volts.
The code has a timer that is programmed to work at 160KSamples per second and to make 4 * 300 samples of acquisitions (fill 4 buffers od 300 samples) and then to stop the timer send the data to serial port in CSV format (program serialChart) and then start the sampling again, by starting the timer automatically. In the program is option ‘q’.
The problem that I am seeing is that when the timer is restarted the voltage reference start from zero and charges, although the variation of the signal (an amplified microphone in my case) appear correctly summed to the DC charging component of the signal.
I also send a plot image of 2 microphones to clarify the problem described.
João Nuno Carvalho