TMS570LC4357: wrong values from AD converter

Steven Wahlberg

Part Number: TMS570LC4357
Other Parts Discussed in Thread: HALCOGEN,

8156.screenshot.zip

Dear TI Community,

I'm new here and have a question please.

I want to capture the data from four microphones, each microphone is connected to an amplifier, and each output of the amplifier is connected to a channel in AD converter. In HALCoGen I configured the Pins 0 - 7- 19 - 20 for ADC 1 Group 1, 12 Bit.

I don’t configured Vccad, Vssad, Vrefhi and Vreflo. I have connected the ground of the microcontroller “TMS570LC4357ZWTQQ1” with the ground of my circuit.

The Microcontroller is connected with my laptop via USB cable and I read the data via SCI.

My problem is, I get wrong values of AD converter. There is no sound and it shows higher values. Please see screenshot

Can you please check in my code whether it is right?

Or I have still something to connect to the microcontroller? For example Voltage Ground etc.

Thank you for your response.

best regards

Jo.

over 8 years ago

0 Bob Crosby over 8 years ago

TI__Guru 72500 points

Did you measure the voltage at the ADC inputs with an oscilloscope? First determine if you have proper voltages at the input (0V to 3.3V).

0 Bob Crosby over 8 years ago in reply to Bob Crosby

TI__Guru 72500 points

This is a duplicate post. The thread continues in the following post:
e2e.ti.com/.../2304676

0 Steven Wahlberg over 8 years ago in reply to Bob Crosby

Prodigy 90 points

Thank you for your reply.

That is the problem. I've looked in both documents “Technical Reference Manual” and “TMS570LC4357 Hercules™ Microcontroller Based on the ARM® Cortex®-R Core datasheet (Rev. C)” but not found which pins inputs are intended for Vccad, Vssad, Vrefhi, and Vreflow.

best regards
Jo.

0 Steven Wahlberg over 8 years ago in reply to Steven Wahlberg

Prodigy 90 points

Hello
I tested it again, now I am sure that my code correctly and the supply voltage of the ADC is 3.3 V.
how can I increase the supply voltage of the ADC to 5 V.
best regards
Jo.

0 Qiu chi over 8 years ago in reply to Bob Crosby

Expert 1210 points

I agree it,Besides,you must make sure your handware reference voltages toADC module.Fox example,Our REFHI=5V,REFLO=0V.

0 Steven Wahlberg over 8 years ago in reply to Qiu chi

Prodigy 90 points

3.3 V form ADC, I only calculated it not measured, my question now is how I can set Vrefhi to 5 V because Vrefhi is now 3.3V .
I use the microcontroller TMS570LC4357
best regards
Jo.

0 Bob Crosby over 8 years ago in reply to Steven Wahlberg

TI__Guru 72500 points

Are you using your own hardware, a TI Launchpad or a TI development kit?

0 Steven Wahlberg over 8 years ago in reply to Bob Crosby

Prodigy 90 points

Yes, I use Hercules TMS570LC43x LaunchPad Development Kit.

best regards
Jo.

0 Bob Crosby over 8 years ago in reply to Steven Wahlberg

TI__Guru 72500 points

On the TMS570LC43x Launchpad to change the ADC from 3.3V to 5V move the resistor from R3 to R4. They are located in the lower right corner above LED3. The Launchpad schematic is here: processors.wiki.ti.com/.../LAUNCHXL2_570LC43_RM57L_SCHEMATICS.pdf

0 Steven Wahlberg over 8 years ago in reply to Bob Crosby

Prodigy 90 points

sorry, I found them, but I don't understand please, what do you mean with move the resistor from R3 to R4 ?
thanks & best regards,

jo.

0 Bob Crosby over 8 years ago in reply to Steven Wahlberg

TI__Guru 72500 points

If you look at page 4 of the schematic you will see the letters DNP next to R4. That means "do not populate". Looking at the board you will see a small zero ohm resistor in the spot for R3, but will see that the spot for R4 is empty. Again looking at the schematic, notice that R3 connects VCCAD to 3.3V. If you remove R3, leaving the spot empty, and put a zero ohm resistor in the R4 location, VCCAD will be connected to 5V. These are very small resistors. If you do not have experience with small surface mount components you should seek someone with the correct tools and experience to move the resistor.

0 Steven Wahlberg over 8 years ago in reply to Bob Crosby

Prodigy 90 points

Thank you very much, it worked now.

Beste Regards,
Jo

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TMS570LC4357: wrong values from AD converter