Faulty TTL input/output (Bpod State Machine r2+)

aaronbwong

Hi Sanworks support,
We have a Bpod state machine r2+ where we are trying to couple in a custom TTL signal from an Arduino Board Micro (5V) into the BNC Input 1. We were testing it as a trigger for change of state using 'BNC1High'. We noticed that it wouldn't trigger, so we checked the Arduino output on the oscilloscope. The output on its own is fine. However, when plugged into BNC Input 1, the voltage can only reach 5-10 mV (!). We are suspecting there is some faulty (short) circuit within the Bpod board. How could we check this?

We have also tested the BNC Output 1 & 2. When directly connected to the oscilloscope, a toggle from the Bpod interface only change the output voltage also around 5-10mV.

Moreover, we wanted to try the Flex I/O wires, but the only example we found is FlexIOAnalogLight2AFC which is not very clear on how to configure the channels.

I look forward to your reply!

Josh

Hello Aaron,

Two things I'd check first:

Does the oscilloscope have a gain setting on the channel? It should be at 1X
Does the issue go away if you swap the BNC cable?

I suspect (1) because both the input and output are reading 5-10mV, while they are mediated by separate systems - the input is connected to an optoisolator (so it's not connected to Bpod's other circuitry at all), while the output is driven by a separate galvanic isolator.

Flex I/O channels are configured from the settings menu on the Bpod Console GUI. More advanced settings can be configured by directly setting BpodSystem.FlexIOConfig. After selecting each channel type, you can open the system info panel (spyglass icon on the Bpod console) to view the event and output channel names.

Josh

aaronbwong

Hi Josh,

Thanks for the prompt suggestion. We double checked all the connection and found out this was actually from a faulty short-circuit connection from our Arduino output cable. The r2+'s input and output seems to function correctly now. Sorry for the false alarm.

On the Flex I/O channels, thanks for the link to the Bpod GUI and FlexIOConfig. The documentation on the FlexIOconfig clarifies a lot. What is not clear to us is how to configure them in the state machine specifications.

If we configure channel 1 of Flex IO as an Digital Output, which output event should we use to set it to high? Is it 'OutputActions', {'AnalogThreshEnable', 1}
Similarly, if we configure channel 1 of FlexIO as Digital Input, can we use it to trigger state changes in the state machine specification? If so, which event should it be?

aaronbwong

Wait, so the list of event names may change after setting the FlexIO config either at the GUI or with BpodSystem.FlexIOConfig? So we need to set the config first and then look at the event names?

aaronbwong

Hi Josh,
Problem solved. We changed the Flex I/O config with the GUI (channel 1 to Digital In, 2 to Digital Out), and indeed now we see the new events 'Flex1High' and 'Flex1Out' and output action 'Flex2DO'.

Thanks so much for the help!