WaveGen: Sine wave generation for Opto experiment

eunkyuhodu

Hello. I am trying to use PulsePal with the laser for a optogenetics experiment. I am very new to PulsePal and am struggling to find a way to trigger an output from Pulse Pal using MATLAB.

I am trying to use the Waveform Generator with PulsePal 2 to generate a sine wave in various frequencies (10Hz, 25Hz, 40Hz). The output should be triggered by MATLAB, not triggered with a TTL signal. I have managed to have the PulsePal be recognized as an object.

P = PulsePalWaveGen('COM3');

using the argument above.
However when I type P.trigger nothing really happens...

Would you be able to provide a example that would generate a sine wave using MATLAB?

Any advice would be greatly appreciated!! Thanks so much!

Josh

Hello eunkyuhodu,

With the beta waveform generator firmware, the default waveform only plays for 100ms each time you run P.trigger(). If you set P.duration to 10, it should play for 10 seconds. To view the waveform on your oscilloscope, try setting the time scale set to 20ms per division and the voltage scale set to 1 volt per division. The input channel should be set to DC coupled and 1X probe, and the trigger threshold should be set to 500mV in 'normal' mode.

That being said, waveform generator is still in "beta" because it is missing features (e.g. a function to stop playback!) If your goal is to play sine waves of different frequencies, you can use Pulse Pal's standard firmare and set up a looping custom waveform with one period of your sine wave. Here's the setup code:

% Setup (run only once per session)
PulsePal('COM3'); 
ProgramPulsePalParam(1, 'CustomTrainID', 1);
ProgramPulsePalParam(1, 'CustomTrainLoop', 1);
ProgramPulsePalParam(1, 'PulseTrainDuration', 10); % Seconds to loop the waveform

% Generate and load waveform
freq = 40; % Hz
amplitude = 1; % volts
myWaveform = GenerateZeroPhaseSineWave(freq , amplitude);
SendCustomWaveform(1, 0.0001, myWaveform);

% Trigger
TriggerPulsePal(1);

Please let me know if this works for you.

Thanks,

-Josh

eunkyuhodu

Thanks so much Josh!

I would have to connect PulsePal to the laser to know if it actually works but the code itself is running without error and I see that the PulsePal is sending the waveforms.

I will let you know if my experiment works!

Thanks!

eunkyuhodu

Hello Josh.

We encountered an error while trying out different frequencies for the sine waves.

This error occurs:
Error using GenerateZeroPhaseSineWave (line 39)
Pulse Pal has insufficient memory to store one iteration of this wave.

This error seems to only occur when I set the frequency to below 20Hz. Can this error be fixed by adjusting the sampling rate or the amplitude? Any insight would be greatly appreciated. Thanks!

Josh

Hello eunkyuhodu,

Pulse Pal's internal memory can store up to 5,000 samples per waveform. At 10kHz sampling, a single period of a 20Hz waveform would require only 500 samples.

Can you please share the code you're using to call GenerateZeroPhaseSineWave?

Thanks,
Josh

eunkyuhodu

Hi Josh
I am using the code below:

% Setup (run only once per session)
PulsePal('COM3');
ProgramPulsePalParam(1, 'CustomTrainID', 1);
ProgramPulsePalParam(1, 'CustomTrainLoop', 1);
ProgramPulsePalParam(1, 'PulseTrainDuration', 10); % Seconds to loop the waveform

% Generate and load waveform
freq = 10; % Hz
amplitude = 5; % volts
myWaveform = GenerateZeroPhaseSineWave(freq , amplitude);
SendCustomWaveform(1, 0.0001, myWaveform);

% Trigger
TriggerPulsePal(1);

Josh

Hello eunkyuhodu,

That code snippet works for me - I don't get an error in MATLAB, and the waveform looks as expected.
Earlier versions of Pulse Pal (v0.X, v1.X) had a smaller SRAM memory, and may have returned the error you're seeing. Are you using Pulse Pal v2 hardware, and the latest version of Pulse Pal software from the repository?

Thanks,
Josh

eunkyuhodu

Hi Josh,

Thanks for checking. But it seems that the code still produces the same error. It works for 11Hz but for any frequencies below 10Hz, the error occurs.
I am using the latest software and we have the Pulse Pal V2 hardware. Can I adjust the sampling frequency to use frequencies below 10Hz?

Thanks!

Josh

Hello eunkyuhodu,

I found the issue - it's in GenerateZeroPhaseSineWave.m
You can safely delete lines 38-40. I added an updated file to the develop branch of the repository. If this works for you, I'll push it out with our next release.

-Josh