Power Profiling an Arduino MKR WAN 1300 using PPK2

Hello, for my EE dissertation I am using the PPK2 to power profile an Arduino MKR WAN 1300 when transmitting. I was under the impression that for a LoRa transmission it would near enough be a nice rectangle, with the height relating to the transmit power, and length equal to the Time on Air (ToA).
Instead, I am getting a bunch of small spikes, like this:

Could anyone help me understand what this means? (btw, I am using PPK2 in ammeter mode, with 5V supply from the USB on my PC).

The MRKWAN 1300 was discontinued due to its poor design for low power and its successor, the 1310 isn’t much better. It’s not helped that it’s a SAMD with an STM32 + SX1276 so there’s two MCU’s doing things at the same time.

So you may find it hard to distinguish between LoRa Tx and anything else going on.

Putting in a digital output to show when the radio has been asked to do something would help - and if you know the duration of the transmission you can match it up. However the firmware on the Murata module is prone to doing its own thing on its own timetable so modem.endPacket() may provoke an instant response or it may wait for a few seconds due to duty cycle calcs.

Thanks for the reply, I agree its a very bad board for low power - I cannot get below 20mA sleep current, but thankfully the objective of the project is to investigate power consumption only during transmission of LoRa.

I changed the USB port on my PC that was providing the power, and that has managed to fix it, and the measured ToA now matches exactly the theoretical calculation:

Have you seen this? Will LoRaWAN IoT device work with a coin cell battery? from figure 7 and forward. You have the processor wake up and doing things + a transmission, and then two receive windows.

I am also using a PPK2 to power profile an Arduino MKR WAN 1310 (not 1300) for my dissertation.
Unfortunately I’m not a EE, and have a question about how you connected the PPK2 to the MKR WAN 1300?

How did you connect the PPK2 to the MKR WAN in source mode?

I used ampere meter mode, as that allowed me to retain access to the serial monitor. It requires using a custom cable like below:


Check out this video from about 7:00 mins: https://www.youtube.com/watch?v=LUB8RWzzLWc&ab_channel=AndreasSpiess

Cant comment on using Source mode, as I didn’t do that.

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