Board does not work unless connected to the computer

[gustavovieira]

Hi all,

I'm currently working on a project using the Freescale Cup cars. I have a FRDM-KL25Z board and a Freescale Cup Shield to control the motors.

However, my board does work any more if it's not connected to the computer. I used to be able to upload a code, disconnect the cable, power the using the shield and a battery and run it. All of a sudden it changed: as soon as I unplug the usb cable, my program stops running.

Does anyone have the same problem? Is there any way to fix it?

I found out that it works as long the USB cable is connected, either on the USB or the OpenSDA port. It seems the cable simply powers the board. But I used to do that with the shield, and don`t know why it no longer works.

[adriancano]

Hi,

Did you check that the battery is ok? You are saying that the program stops running , this means that the board is still powered but the program does not do anything? Or is that the board is completely off.

Regards,

Adrian

[gustavovieira]

The battery is ok. It is used to power the motors, and they are working normally.

When I unplug the cable the program does not do anything, and the board light is turned off, so I believe it's not powered. The shield has a light indicator for the battery, and it remains lit, but the other LEDs are turned off. I suspect that, for some reason, the shield is no longer providing power to the board, but I don't know why it would happen.

Thanks for the quick reply!

Regards,

Gustavo

[adriancano]

Definitively the FRDM board is not being powered by the Shield. The shield take the Battery voltage to the pin 16 in header J9 and with this the FRDM board is powered.

You said tha only one led is on and this one indicates that the battery is charged and plugged, the other leds in the shield are not powered because this are turned on or off by the FRDM but this is off. You can make a test, supply 5 or 9 volts to the pin 16 in the header J9 (P5-9V_VIN) without the shield and see if the board is powered, if not you need to check the continuity between the Vbat pin in the shield and the pin 16 (J9) in the Freedom board when this are together.

Please let me know your results.

I hope this information can help you.

Regards,

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[gustavovieira · Accepted solution]

Sorry for the delay to get back, I did not have access to the board before today due to a holiday.

I made the tests you suggest, and the board is indeed not being powered by the Shield.

• The board is powered and works properly when I supply 5 volts to the pin 16;
• There is continuity between pin 16 in the board and Vbat in the Shield;
• The Vbat pin in the shield is not powered when the battery is connected.

We investigated more and found the reason: the connection to the Vbat pin is damaged, as seen on the image below.

I don't know why it was damaged, but I believe we could fix it by manually connecting the output of the 5V DC-DC converter to the Vbat pin. Do you agree with this solution? Is there any other possible one?

My colleague had the exact same problem with his FRDM-TFC Shield. Do you know why this damage might have happened?

Anyway, thank you for the orientation. It helped us find the cause of the problem and a possible solution.

Regards,

Gustavo

[adriancano]

Hi,

I am not really sure about the causes of this problem, but this happened for sure because this is a line that carries a big amount of power. The solution you said I believe is good enough, because the FRDM board needs from 5 to 9 Volts in the that pin to work.

If I have more information about this issue I will let you know.

Best Regards,

Adrian.

[BlackNight]

Does your shield need 5V power from the FRDM board? That 5V is only generated from the USB, and not from the battery.

This is a common issue with motor shields, see FRDM-KL25Z with the Arduino Motor Shield | MCU on Eclipse.

On newer FRDM board revisions you can solder a DC-DC converter to generate 5V from the V_Bat, see

http://mcuoneclipse.com/2013/06/21/5v-generation-from-v_in-on-the-freedom-board-reve/

I hope this helps,

Erich

[gustavovieira]

Erich, I would need to check the documentation to answer surely (can't do it now on my mobile), but I don't think this is the case. If it was so, the car would only work when the board was powered by the USB cable. However, it used to work just fine powered by the battery alone. It simply stopped working suddenly. Do you think this converter could solve the problem?

Thanks for the reply,

Gustavo

[BlackNight]

I don't have the schematics of that board. But if it worked before, then probably it had a 5V DC-DC converter on the board already. It could be that this one has been damaged (over-current?). I suggest you check the schematics and make a diagnose what is not working, and why.