I am a hobbist with electronics than a real engineer, so I think I may be lacking some basics, but I am trying to connect green led diode to the FAULT pin in DRV8825 (and minus to the GND in arduino nano), so it lights up when it’s working properly (I’ve read it should be HIGH when it’s ok). I’ve checked with my multimeter that there is around 3.5V on the FAULT. However, when I am connecting a led to the circuit (without any resistor) it doesn’t light up. After checking the voltage it drops to 1.7V when the led is in the circuit. I am sure the diode is working properly (I have another circuit). I tried with red diode and I can see the diode lights up slightly (red diode has lower voltage as far as I know). What do I do wrong?
The FAULT output on the chip is open drain and goes low during a fault condition. It will not drive an LED in a no-fault condition, as the output is in a high impedance state with a 10K pullup.
Connect the LED between Vcc and FAULT, and if properly oriented the LED should light during a fault condition. There is a 1.5K current limiting resistor on the breakout board.
