Help with hooking up a 5V logic converter

[chrismas9]

@felixsc1, What is the device you are trying to drive? What is the actual spec for logic 1 voltage? Many CMOS devices are 0.7 VCC or 3.5V with 5v supply. These work fine with the greater than 4V from USB and V+ pin.

If you only want a 5V output there is no benefit from using the Sparkfun level translator. It relies on a 10k pull-up to HV to get a high level. You will get the same result by programming the pin as Open Drain and adding a pull-up resistor to 5V or V+.

[felixsc1]

@felixsc1, What is the device you are trying to drive? What is the actual spec for logic 1 voltage? Many CMOS devices are 0.7 VCC or 3.5V with 5v supply. These work fine with the greater than 4V from USB and V+ pin.

If you only want a 5V output there is no benefit from using the Sparkfun level translator. It relies on a 10k pull-up to HV to get a high level. You will get the same result by programming the pin as Open Drain and adding a pull-up resistor to 5V or V+.

More specifically, I want to trigger this device: http://www.ampi.co.il/isoflex.html
Unfortunately, I don't have the datasheet, but it says that the input voltage should be 5-10V. It will generate a current output for the duration of the TTL pulse. I tried triggering it with the pyboard 3.3V output without success (at least I am pretty sure it didnt work, but it could be that I didn't measure the current output properly , since I don't have any experience with these things, I am a a biologist).

[pythoncoder]

In the absence of any electrical data it's impossible to be sure. I'd suggest defining the output as open drain and supplying a pullup resistor to 5V. Start with a value of 1KΩ. If that doesn't work try reducing the value but don't go below 220Ω.