Description
Subject of the issue
On the ESP32, the delayMicroseconds() function is a busy-wait. This is a problem with using Free-RTOS on the ESP32, as it holds up the processor, preventing it from doing anything else. On the other hand, the delay() implementation is non-blocking. This works because the RTOS tick frequency is once every millisecond(1 kHz).
In this library, there are 2 instances of delayMicroseconds(), both for 500 microseconds. I recommend making it 1 millisecond delay with the delay() function instead. Both are delays to wait before checking if bytes are available from u-blox GPS. I don't think there will be any issue waiting for a little bit longer before checking again.
The two locations of these delays are here:
Your workbench
- What development board or microcontroller are you using?
Custom dev board integrating ESP32 and U-blox MAX M8Q, connected over UART bus. - What version of hardware or breakout board are you using?
ESP32 + U-blox MAX M8Q - How is the breakout board wired to your microcontroller?
UART connection - How is everything being powered?
3.3V VCC powered via USB and regulated. - Are there any additional details that may help us help you?
I am using FreeRTOS with the ESP32. I use theCallbackExample1_NAV_PVT.inoimplementation in the Examples folder. Link
Steps to reproduce
Create an RTOS thread to run the code on CallbackExample1_NAV_PVT.ino
Expected behavior
It should be able to poll the GPS, but return back to doing other tasks while waiting for a response from GPS.
Actual behavior
It is spending a long time waiting for the GPS to respond, holding up the processor from doing other things.