I would like to measure the power consumed (or current drawn) by an RFM69HCW 915 MHz module (picture below) connected to an Arduino Pro Mini (on a customized board). I put the radio to sleep for 750 ms, then it wakes up for 250 ms and then goes back to sleep, so on and so on. How do I use an oscilloscope to see the current drawn by the radio module?
Here is what I tried: The RFM69HCW module is supplied with 5 V, which is brought down to 3.3 V using resistors. A voltmeter across the VIN and GND pins show 5 V. In the picture above I circled a pin in red on the RFM69. A voltmeter across that port and the GND pin shows that the voltage toggles between 3.3 V to 0 V, and I guess that is due to the radio going to sleep and waking up.
To reiterate, I know that to measure the current I have to put the probes of the oscilloscopes in series in the circuit. But which pins do I probe?
FYI, I can use the radio to receive data from a transmitter. I can use the data to perform tasks on the Arduino. So the hardware and software work fine.