I have written the first version of a C program for the Raspberry Pi Pico. The Pico is powered from the 3.3V LOAD pin of the aemlic board. The Pico is also connected to a Raspberry Pi 4 8GB Linux computer, using the SWD pins for downloading programs, and the UART pins (serial interface) to send print() messages from the Pico to the Pi4. The purpose of the program, for now, is to log what happens on the aemlic.

The program starts to run as soon as the aemlic provides 3.3V. As long as it has power to run, the Pico blinks the on-board LED once per second. It counts the seconds, and prints a status message every minute. I am using this to learn how long the Pico can run, depending on the initial voltage of the LIC. When the LIC is just barely charged, the Pico runs for about 20 seconds. When the LIC is fully charged to 3.8V, the Pico runs for at least 20 minutes and maybe much longer. My testing has not yet been comprehensive.

I will probably start a new hackaday project to keep track of this Pico project, including the C code.