NI USB 8451 with external power source

[Sanguigui]

Hello everyone !

I try to figure for 2 days now why my USB 8451 gave me an error 301740 : SDA or SCL line or both are in a low state or there are no pull-up resistor.

I try to change a multiplexer channel in order to obtain a temperature mesurement from a sensor. I checked my SDA and SCL lines, thye're both in high state and i have 2 pull-up resistors with a value of 10K.

The only change with my older circuit is that  i use an external power supply for my electronic chip and a MUX PCA9543(texas instruments) to select the sensor of which i need the data .

Does anyone have encountered similar issues ?

[Sanguigui · Accepted solution]

Ok guys,

apparently, the ground of my usb 8451 wasn't connected to the ground of my power supply, it is not working yet but my components are responding !

[Sanguigui]

Everything is working fine with the tied grounds, Don't forget to do it!