DAC9881EVM-PDK: Action potential generator

Huy Cu

Part Number: DAC9881EVM-PDK
Other Parts Discussed in Thread: DAC9881, DAC9881EVM, DAC8811, ENERGIA

Hi,

I have couple questions

1/ I would like to create the action potential. Can this DAC board help me to do that? My requirements are low noise and high resolution.

2/ Is this better to use DAC9881 or audio DAC series: http://www.ti.com/audio-ic/converters/dac/products.html in this application?

3/ In case, I would like to modify the shape of the waveform, let's say make it faster, bigger, can DAC9881EVM do that?

4/ What is the software that I can use to create my arbitrary waveform? (Matlab, Labview, etc.)

Thank you.

Best,

over 7 years ago

0 Uttam Sahu over 7 years ago

TI__Genius 14220 points

Hi Huy,

Welcome to E2E and thank you for your query. Please find my answers below:

1. You can use DAC9881EVM in bipolar operation mode to generate the action potential. The resolution and dynamic specs (noise, settling time) of DAC9881 should be good enough for the requirements of the action potential
2. I don't think you need an audio DAC for this. You can either use DAC9881 or DAC8811. But in case you have the action potential data as an audio file, you may choose to use an audio DAC to interface easily
3,4. The EVM's are mainly for evaluating the performance of the DAC and hence, don't have full-fledged software interface for custom code development. I would suggest you interface the EVM with a microcontroller that supports software interfaces like "Energia" or CCS so that you can codify the equation for action potential and consequently, program the codes to the DAC with SPI.

Hope I have answered your question.

Regards,
Uttam Sahu
Applications Engineer, Precision DACs

0 Huy Cu over 7 years ago in reply to Uttam Sahu

Prodigy 40 points

Hi,

Thank you for your answer. In summary, I have signal stored on my computer under .txt format. I would like to stream it from my computer to the DAC board and convert into a real signal. As your recommendation, I will go with those two boards:

1/ DAC9881 Performance Demonstration Kit: www.ti.com/.../DAC9881EVM-PDK

2/ TM4C1294 Connected LaunchPad: http://www.ti.com/tool/ek-tm4c1294xl#technicaldocuments

My questions are:

1/ What is the difference between EVM and PDK? If I buy the PDK, should I be able to interface with my computer, or I still need the TM4C1294?

2/ Is there anything missing that I have to buy to finish my application set up?

Thank you.

0 Uttam Sahu over 7 years ago in reply to Huy Cu

TI__Genius 14220 points

Hi Huy,

The PDK contains the programmer that interfaces to the custom GUI made for the EVM. However, for your application it is better that you only get the EVM and then connect with the TM4C1294 Launchpad and program with C code or Energia. You need to connect SPI lines from the Launchpad and external power to the EVM. This should get you started with your application.

Regards,
Uttam

0 Huy Cu over 7 years ago in reply to Uttam Sahu

Prodigy 40 points

Hi Uttam,

I am testing the DAC9881 EVM with Arduino. The Arduino uses computer source and EVM uses an external 5V source (www.youtube.com/watch. SPI lines connect to EVM P2. Analog data were measured from J4-2.

I have trouble with Vref. VrefL = 0.384V and VrefH = 4V, which should be 0 and 5V respectively. These are other measurements from TPs:

TP1: 0.002 (V)
TP2: 0.002
TP3: 2.200
TP4: 4.96
TP5: 0.002
TP6: 0.002
TP7: 0.042
TP8: 4.96

When I powered the EVM only, the output signal is biased by ~1.3V. When Arduino was plugged in, the biased is ~0.7V. Please help me on this. Thank you.

Best,

0 Uttam Sahu over 7 years ago in reply to Huy Cu

TI__Genius 14220 points

Hi Huy,

The YouTube video is a bit lengthy. Couldn't watch it. Can you tell me what is the supply voltage? The reference source needs higher than 5V input to generate 5V output. The reason for the floating output might be because you may have some of the nodes floating.

If you can upload the schematics (power supply and Arduino connections), it will be easy to understand.

Regards,
Uttam