Did I Fry my Op Amps? | Cypress Semiconductor
Did I Fry my Op Amps?
I modified the ADC_Differential_Preamplifer project to work with a PSoC 4 BLE Pioneer Kit and with a load cell as shown in the attached schematic. It worked initially, reporting mVolt values between about 70 (IIRC) and 1024, which is the maximum.
I then tried to do something fancy by using the redExcite and yellowExcite pins to reverse the polarity of the excitation voltage between ADC readings, intending to subtract the reversed-polarity measurement from the normal-polarity measurement as a means to effectively double the resolution. After failing to get that to work, however, I returned to the project I saved before trying this change.
The problem is, now the first project doesn't work either. The ADC is showing no change of values when the load on the sensor changes. Checking with two DMMs, I can see that the differential voltage going into pins blueSense and whiteSense still varies consistently versus load as it always has. Measuring the voltage between Out_1 and Out_2, however, which should be exactly the same as is being fed to the ADC, reads only 0 V, occasionally drifting to -0.1 mV. Since the firmware only calculates down to values of 1 mV, it makes sense that mVolts is always equal to previousValue so that nothing is being written to the UART.
Did I fry my opamps? Fortunately, I have another kit or two on their way, but I would like to know if the opamps are, in fact, fried, or whether I have some other error in my project that I am missing. I can share the rest of the project too, if that will help.