Powering Tiva C using VBus

Julia London

Prodigy 150 points

Other Parts Discussed in Thread: EK-TM4C123GXL

I'm trying to power my Tiva C module using a 5V step down regulator which is connected to a 9V battery.

The Tiva C is connect to a BlueSMiRF to the following ports

UART1 Rx

UART1 Tx

3.3V output

And an Xbee series 1 to the following ports

UART5 Rx

UART5 Tx

3.3V output

The Xbee and the BlueSMiRF power up when I connect the 9V battery, but the LED flicker from the Tiva C doesn't turn on, nor does the code work.

I'm not sure if it's a current thing or grounding problem because when I connect the battery to the Tiva C and the Tiva C's USB port to the computer, everything works correctly (But both the battery and the serial USB connection have to be connected.

over 8 years ago

0 Amit Ashara over 8 years ago

TI__Guru**** 244380 points

Hello Julia,

TM4C can only be powered by 3.3V. You are exceeding the max operating conditions.

Regards
Amit

0 Julia London over 8 years ago in reply to Amit Ashara

Prodigy 150 points

I don't think that's true.
In my embedded systems class that's how everyone is powering their robots: by powering the Vbus pin with 5V on the first pin in the J3 column so that the Tiva C TM4C123GH6PH
And all the bots function correctly. And my professor has been teaching with this microprocessor for this class for several years.

But even if that is the problem, there is too much voltage, that doesn't explain why the LEDs aren't working correctly.

0 Amit Ashara over 8 years ago in reply to Julia London

TI__Guru**** 244380 points

Hello Julia,

Do you mean to say that you are using EK-TM4C123GXL LaunchPad?

Regards
Amit

0 Julia London over 8 years ago in reply to Amit Ashara

Prodigy 150 points

Yes

0 Amit Ashara over 8 years ago in reply to Julia London

TI__Guru**** 244380 points

Hello Julia

1. What is the current rating of the battery?
2. When you only power the system from USB does it still fail in the same manner?
3. If you connect the debugger and check where the does code fail?

Regards
Amit

0 Julia London over 8 years ago in reply to Amit Ashara

Prodigy 150 points

1. 2.1 [A] Duacell Alkaline 9V battery
2. If only powered by USB then the Xbee and the BlueSMiRF aren't powered
3. The code doesn't fail it works properly because when connected with the USB and battery everything runs smoothly, all the commands work

0 Julia London over 8 years ago in reply to Julia London

Prodigy 150 points

the regulator only outputs 600mA and 5V

0 Amit Ashara over 8 years ago in reply to Julia London

TI__Guru**** 244380 points

Hello Julia,

Please correct my understanding

1. The 9V, 2.1A battery goes to a regulator which outputs 5V @ 600mA (max). The output of the regulator supplies the EK-TM4C123GXL's 3.3V regulator for powering the TM4C123 and the wireless modules
2. There is a common GND between the 9V battery, the 5V regulator, the EK-TM4C123GXL and the wireless modules
3. Based on the current consumption of the TM4C123 and wireless modules, the 3.3V and 5V regulator should be able to supply enough current.
4. The output of the 9V battery provides enough current without voltage dropping down which may cause the 5V regulator or 3.3V regulator to fail.

Regards
Amit

0 Julia London over 8 years ago in reply to Amit Ashara

Prodigy 150 points

That is all correct.
But after reading it out loud I realize that I might be a soldering problem.
Do you have any options on what type of hookup wire should be used in soldering all of this together?

Thanks for the help,
Julia L.