I am using an ArduinoFio and a BC127 (datasheet). I'm having troubles getting the serial connection working properly from the Arduino to the BC127 and viceversa. I wasn't able to communicate with the BC127 and I don't know if is because isn't correctly powered on or something else.

I've connected pin 0 of the BC127 to GND, pin 33 to 3V3 and pin 41,42 (RX, TX) to the TX, RX arduino's pins.

I've tested with the tester that all wires are connected, but the BC127 seems dead.

Any help is appreciated :|


There's a couple of things I would try.

First: Don't use the native Arduino TX/RX pins, they should be left alone to talk to the computer. Use SoftwareSerial instead in start a separate serial connection.

Second: Check that Arduino TX pin (that you declared in softwareSerial) is connected to the BC127 RX and vice versa. Unlike just about every other connection in electronics, serial connections need to have their pins reversed so that TX talks to RX. It's an easy mistake to make and one I've made when not paying attention to what I was doing.

Third: Flow control.

If the BC127 sends data when the Arduino isn't listening the data could be lost, to prevent this the BC127 won't send until the Arduino signals it is ready through flow control. See the BC127 datasheet page 8, pins 40 and 43. Trying tying UART_CTS to 3V3 and UART_RTS to Ground. That should cause the BC127 to be in a constant 'send' state.

Lastly I'd hook up a couple of LEDs to pins 37 and 38. They should give you some sort of status indication that could be useful in debugging future problems.


use this method for dealing with voltage translation. Also we have IC's which does the level shifting. Works great with higher frequencies as well.

Voltage Translation using nMos


Use voltage level translator. 5v to 3.3V. Dont just connect directly 5v tx to a 3.3v tx...!!

  • Do you mean 5V tx to a 3.3V rx? – Nick Gammon Jun 24 '16 at 0:37
  • Yes I would use a N channel Mosfet to make 5v to 3.3V communication. – AjaY Dillikar Jun 24 '16 at 6:28
  • 3
    Your answer is likely to get more votes if you describe how to do this. Perhaps a schematic. – Nick Gammon Jun 24 '16 at 6:41
  • Sure I will post the schematic and how I deal with voltage translation devices. – AjaY Dillikar Jun 24 '16 at 6:42

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