[HeRos] Saving Private Ryan

This allusion to the movie is not chance, we have lost 2 HeRos today and we are trying everything to get them back. The problem is that the UART 4 which talks to the Pololu doesn’t work any more. Thus, we are not able to send anything to the Pololu and the HeRos don’t beep or move any more.

What’s happen ?! Charles was working on IR transmission and trying the new body (by the way so sexy :D).

Firstly, just one didn’t respond. He asked Flo to look why and took an other one. However quickly the second stopped working too. As a result, we believed that the Pololu was guilty. We made some test with the oscilloscope and we saw that on the UART from the stm32 to the Pololu we had 2V instead of 3.3V. Moreover we saw that during the transmission we went to 0, but the signal had difficulty to be back high quickly. Alexandre, a member of the robotic club, were in A406 and we asked him if he understood something. He explained us that the pull up might be damaged since even at the end of a transmission the signal took too much time to be back high. In order to see the difference, I looked at the oscilloscope the UART when the baud rate was set to 6200. The voltage was still 2 V but now the signal were almost able to be high (1.8V).

Alexis advised me to test the PCB without a Pololu. I picked a cable with one side with an USB and the other side with wires in the air. I soldered the wires on the base were we put in the pololu and I made new test with the computer.

Test HeRos without Pololu

I got one good news, I have 3.3V again! But the UART still doesn’t work:

Message on UART 4

Set of messages on the UART

A message with high baud rate

A message with high baud rate

A message with low baud rate

A low baud rate message


I will ask Alexis help because I am overwhelmed.

Today, I installed a Windows Virtual Box. I need it to to use one software to flash the ATtiny with a boot loader and a second software to use the boot loader in order to flash my Application. However, I am a little confused so I will ask a teacher instead of doing a mistake.
Here links :
The machine : http://www.elnec.com/products/device-programmers/beeprog
Boot loader : http://jtxp.org/tech/tinysafeboot_en.htm

See you tomorrow with better news I hope 🙂


Eric Masseran


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