SparkFun Forums

[United]

I have a question regarding Rx and Tx pins of SMIRF 2.0

From my understanding, Tx is output pin and Rx is input pin.

If there is no input, it should be High (stop bit)...
so basically if I just connected SMIRF to power and ground only, Rx pin should be high as there is no input.
However, I am getting Rx pin as low... which is Start Bit.... but there is no signal received........ (the base unit is not even started)

[sparky]

During idle the SMiRF TX pin (output) will be high.

RX is an input pin. I believe it is tied high through the PIC's internal port resistor, but to be safe you should pull it high through a 10k resistor if you are not going to use it.

You cannot probe an input pin and get a sensible reading.

I believe you have your pins mixed up. TX will output a high value until something is received across the link. RX just sits and waits for the input from your micro.

-Nathan