Part Number:MSP430G2553
Hello,
I am trying to sample current with the 10bit adc of the msp430g2553 mcu by converting it to voltage.
I have a simple photo diode which outputs current.
I connect its output to ground through a resistor of 50k ohm. I then measure the voltage drop on the resistor using the adc. It doesn't work. When the resistor is connected to the adc pin then I measure a voltage of around 2.75V using my multimeter. When I disconnect the adc pin then I measure 100mv on the resistor which makes sense.
Why does connecting the resistor to the adc pin create this problem?
What am I missing?
I am using one of the code examples in CCS for 10bit ADCs using 1.5v reference voltage with interrupt and DTC.
By the way, if I connect to the same adc pin a voltage source then the measurement is fine and isn't altered.
Thanks,
David