Power to F28027 in Standalone Mode

LAURA SANDOVAL

Hello,

I am currently running a code that measures the voltage through the ADCINA4 pin (J1.6) and displays the results on a LCD screen. I am doing this is two ways:

First, I use a USB to power the LaunchPad and view the results on Code Composer Studio (the LCD also displays the results viewed in Code Composer Studio simultaneously).

Second, I use a battery (with a 3.3 V voltage regulator afterwards) to power the LaunchPad in standalone mode using the J3 pins (on the bottom right-hand side of the LaunchPad). Also noteworthy, I have f2802x_codestartbranch.asm and F28027.cmd in the project. Also, I put the third S1 switch in the down position in this standalone mode and all jumpers are connected.

I compared the results of the C2000 LaunchPad with those on the DAQ (or multimeter...either works) and they are much more accurate and consistent when the LaunchPad is being powered with the USB.

I looked for documentation on how to power the F28027 in standalone mode and I haven't seen anything so far. I would be greatly appreciative to be directed to a place where I could do more reading on powering the F28027 in standalone mode. Of course, suggestions on how to improve my setup are appreciated as well.

over 11 years ago

0 Gautam Iyer over 11 years ago

Guru 192875 points

Hi Laura,

Just to confirm: F28027 with USB delivers more accurate results than when connected with battery, right?

If so, this should not happen until battery is not able source the current required by the board.

Regards,

Gautam

0 LAURA SANDOVAL over 11 years ago in reply to Gautam Iyer

Intellectual 360 points

Thanks for your suggestion Gautam. I measured the current going to the LaunchPad with a multimeter and it was 155 mA. I read from the data sheet on the TI website (http://www.ti.com/lit/ds/sprs523j/sprs523j.pdf) that the max current consumption is 100 mA. I have attached a plot of some of my results as well. The y axis is the difference between the mean DAQ and LaunchPad values (in mV). Still trying to figure it out.

0 Gautam Iyer over 11 years ago in reply to LAURA SANDOVAL

Guru 192875 points

Ok, just went throug your graph. Yes the values seem to be deviated; this might also happen if the ADC reference value gets deviated. Check that value too.

Regards,

Gautam

0 LAURA SANDOVAL over 11 years ago in reply to Gautam Iyer

Intellectual 360 points

Thanks for your suggestion. This may seem like an elementary question, but how do I sample the ADC reference values (VREFLO and VREFHI) if they are not defined in my current code?

0 Gautam Iyer over 11 years ago in reply to LAURA SANDOVAL

Guru 192875 points

Correct, I assumed you might be using an external source for Vref. Ok, can list your battery specs?

Regards,

Gautam

0 LAURA SANDOVAL over 11 years ago in reply to Gautam Iyer

Intellectual 360 points

Hi Gautam,

Thank you for your response. I have attached a picture of the simple setup. I am powering the c2000 LaunchPad with a 6V battery (with a 3.3 V voltage regulator between them). The LaunchPad displays the results on a LCD which is being powered by the same 6V battery (with a different 3.3 V voltage regulator in between). The voltage is being changed by a potentiometer. The DAQ is used as a control. Do you have any suggestions? I appreciate your time!

0 Gautam Iyer over 11 years ago in reply to LAURA SANDOVAL

Guru 192875 points

Do you have any suggestions? I appreciate your time!

Try eliminating the LCD for now and check the results. Let me know if you get any better results.

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Power to F28027 in Standalone Mode