Flashing LED with Waveform

tanner.stevenson

I was wondering what is the recommended way to flash an LED with a waveform, similar to the way I can play a sound using the PsychToolbox? If the Analog Output Module is recommended, is it possible to accomplish the task with just the Bpod itself?

Josh

Hi Tanner,

If you want to modulate the intensity of a "Chip on board" LED, you can use the analog output module to drive Sparkfun's FemtoBuck LED Driver (or PicoBuck if you need more channels), or BuckPuck if you need more power.

The state machine onboard hardware does not have the ability to store a waveform and play it back, unless you need a simple repeating pulse (e.g. this example, using global timers to flash LEDs in parallel with the flow of states). For light intensity modulation beyond "on" and "off", you'd need the analog module.

-Josh

tanner.stevenson

I see. Thank you Josh!

tanner.stevenson

Is it possible to use Pulse Pal instead of the analog module?

Josh

Yes - Pulse Pal can play trains of pulses with software-defined amplitude.
The only limitations are:

1.
The trigger from the state machine is a TTL - so you need to load the parameters of your stimulation waveform before each trial. With the analog output module, the trigger from the state machine is a pair of bytes that can indicate any subset of waveforms or channels to play back - so you can play different stimulation patterns depending on how the animal decides to move through earlier states of the trial.
2.
The sampling rate is limited to 10kHz (100 microsecond pulses)
3.
Parametrically defined pulse trains can play for up to 72 minutes, but custom defined pulse trains (sample-wise) are limited to 5,000 samples. The analog output module can store up to 64 waveforms of 1M samples each.

-Josh