LAUNCHXL-F28377S: Sine output on buffered dac example program

Nakon Efekata

Part Number: LAUNCHXL-F28377S

Hello

i just got launch pad and i tried running the buffered dac sine example and i got confused at which pin i should probe
on the pin diagram i got with the unit there are dac1, dac2, dac3, dac4, while on the user guide there is daca, dacb, dacc, dacd

while runing in debugging mode i can see there are values in daca registeres, and i tried scoping all of the four dacs from 1 do 4 and i get 0v at all the outputs

am i probing the wrong pins or is there something else im doing wrong here?

over 7 years ago

0 Frank Ankapong over 7 years ago

TI__Mastermind 28275 points

Hi Nakon,

The F28377S device on the LAUNCHXL-F28377S has 3 real analog dacs -> daca, dacb, dacc. The dacs dac1...4 are not real analog dacs but implemented using PWM and LPF on the output of a GPIO pin. The buffdac_sine example uses daca, dacb or dacc.

The outputs of daca, dacb and dacc come out on ADCINA0, ADCINA1 and ADCINB1 respectively. On the LAUNCHXL-F28377S, you can find the corresponding pins on J3 Pin 27 (ADCINA0) , J3 Pin 29 (ADCINA1) and J3 in 24 (ADCINB1).

0 Nakon Efekata over 7 years ago in reply to Frank Ankapong

Prodigy 120 points

Tried it, still no ouput on any of those pins

0 Frank Ankapong over 7 years ago in reply to Nakon Efekata

TI__Mastermind 28275 points

By default, the buffdac_sine example uses VDAC as the dac reference so a voltage 2.4v to < Vdda needs to be supplied to the VDAC pin (ADCINB0). Alternatively, you can change the reference to REFERENCE_VREF in the code and recompile.

0 Nakon Efekata over 7 years ago in reply to Frank Ankapong

Prodigy 120 points

Thanks,
I tried supplying 3.3v to the VDAC pin but i didn't have any luck, but setting refrence to VREF solved it

0 Frank Ankapong over 7 years ago in reply to Nakon Efekata

TI__Mastermind 28275 points

Glad i could help. Let us know if you ran into any more issues.

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LAUNCHXL-F28377S: Sine output on buffered dac example program