No i2c devices found using scanner

I hooked up an arduino variant (nodemcu) to a pn532 rfid module setup in i2c mode. The module has three modes, the remaining two are spi and hsu. I’ve used the 4 pins labeled for i2c.

It’s important to note other devices are working correctly. An LCD display turns out the i2c address right away.

The error I’m encountering is the scanner code is going through all addresses up to 0x66 and then doing a stack dump. Then a soft reset on the unit and the cycle restarts.

Any ideas what could be causing this?

Try changing switch 1 to zero and switch 2 to 1, just in case the silkscreen table has switch 1 on the right.

Pete

the switches are correct... check wiring otherwise your board may be bad

I believe the board is bad. I've ordered another one.

Post your code.
Most likely that's where the problem is: iyt sounds like you're blocking too long, not allowing the background processes to run. Add yield() or delay(0) statements at strategic places.

I believe the OP is just tying to scan i2c address using a scanner and it works for the LCD

dhtmldude:
the scanner code is going through all addresses up to 0x66 and then doing a stack dump.

Is there anI2C device that is supposed to be at address 0x67?

wolframore:
I believe the OP is just tying to scan i2c address using a scanner and it works for the LCD

Me too.
Most commonly the I2C backpack of an LCD has address 0x27 or 0x3f. That’s <0x66. Blocking code on the ESP will cause stack dumps.