[HeRos] After the storm, the sun !

Today was a trying day nevertheless efficient. The reason was that we have solved two problems. The first one referred to my post of yesterday and the second one arrived just after we solved the first problem.

The first problem was that two HeRos were not able to transmit data over the UART to the Pololu. The transistor was probably damaged. We still were able to oscillate but at low frequency since the up time was very long. An other strange fact was on the voltage of the serial RX transmission. When the HeRos was connected to an USB port of the computer we had 3.3V contrary to with a Pololu where we found 2V. Alexis solved the problem by adding a pull-up to the line. Now, we set the pin as open drain and we only drive the low level. The HeRos are able to use the Pololu again.
However, one HeRos was a little bit more damaged. We were not able to drive the RX pin and the maximal voltage was 1.2V. Maybe we will look next week with Alexis in order to bring him back. By the way, we still have no idea how did the Pololu damage our HeRos.

The second problem was easier to solve and a kind of funny (when we understand it, of course). On one Pololu, the camera didn’t work any more except sometimes during a global shot. We concluded after debugging our code that it was good, on top of that the same code was working on other HeRos. We pointed out that the camera only worked when the red led 3 was lighting. After looking on the schema, we saw that the pin is between the Uart3_Rx and Uart3_CTS and we might have a contact.

With all the problems, we are delayed on the external modules but we are still good. I took pictures tonight with Charles, have fun 🙂


Global Shot Demonstration

HeRos touched by a global shot

Direct Shot Demonstration

HeRos touched by a direct shot


HeRos in darkness

HeRos in darkness


[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 🙂


[HeRos] In action

During the night, Flo has changed the board.h to the default datasheet settings whereas I have write a function which initialize all the ports with “palSetPadMode(port, pad, mode)” from ChibiOS. And… /* Wait for it */

…this morning our first PCB is working fine ! We can load ChibiOs and through the shell we can start tests. The first one concerns the 4 RGB leds:

Next, we continue with speaking with the pololu thanks to a serial port. We send a command to the STMF32 and it forwards it to the pololu. With the keyboards, you can go forward, backward, leftward and rightward.
And this is the result :

The next steps are :

  • Charles will implement the IR
  • Flo will play with Wifi
  • I will take picture from me with the camera 🙂

Now, it’s time to eat


Power Supply for HeRos

This morning, I analyzed every components in order to get the voltage and the peak current. I looked at the pololu 3pi data-sheet how does the power supply work.

The pololu supplies 3 tensions:

  • Vbat : from the battery (3.5V-6V)
  • Vboost : Vbat with a boost module (9.25V) for motors and IR diodes
  • Vcc : Vboost with a linear regulator (5V) for logical electronics

Since every components are compatible with 3.3V or less, we can take Vbat without having a lack of voltage at any time. Only IR transmitters must not be supplied with more than 1.7V, we will use resistors in order to decrease the tension. The energy loss are not so big because the transmitters don’t work every time. We chose a buck switching regulator to get the 3.3V from the Vbat.