Today, I started to implement the code necessary to test the possibility to use WiFi for time reference between Phyllos as explained in this post. Although we mainly use ChibiOS for our applications, the documentation for ESP32 is in FreeRTOS so the code for this test will also be using FreeRTOS.
The plan for the test is to connect as many devkitC as possible to a main board (here it will be an Olimex E407 programmed with ChibiOS). The main board will be the master over one of the devkitC. When it will start the test, the slave will broadcast an UDP packet. Afterwards, every devkitC will raise an interruption on the main board upon reception of the packet. As the main board will record the time lapses between each reception, we will be able to conclude whether this solution is reliable for time reference. Also, since we can accept at least 1ms of delay between the first and last receptions, the mistakes in the reception time originating from the treatment of the interruption is negligible.
We hope to conduct the test on Wednesday as we are supposed to receive around 10 devkitC on that day. However, the actual number of devkitC at our disposal may be less than those 10 as we must share them with Touch.