Serial signal going right through picaxe?

[asagohan992]

I am using an AXE020 project board with a PICAXE 28X1. I have connected a serial cable's RX wire to input 0 and TX to output 1. The other end of the serial cable is connected to my computers serial port. When I go to the picaxe programming editor terminal and type a character into the output buffer and send it. It comes straight out on the input buffer. The picaxe chip is not being powered at all. No matter which input or output wire I put the RX wire on, the character keeps going straight through. It only happens if the TX and RX wires are connected to the output and input of the board. Does anybody know what is going on here?

 

[womai]

You already gave the answer yourself (sort of): "The picaxe chip is not being powered at all." That means the Picaxe's supply is free floating. In that case, anything can happen - meaning what you are doing is outside any spec. So when you send a "1" through the serial line, it seems that also pulls the output high. If you send down a "0", then the output will be low since there is nothing that can pull it high. Which explains why the output pin echoes the input.

Easy solution: power up the Picaxe and that behavior should stop.

 

[moxhamj]

I'm not exactly sure but picaxes certainly can do odd things when not powered. At the very least, give it a proper power supply! Is the problem still there when the picaxe has power applied?

 

[asagohan992]

Thanks for the help. It was still happening when it was powered i think...
Anyway, somehow the ground wire from the serial cable got disconnected from the picaxe ground and I didn't notice. I think that is why it was happening. After I reconnected it, it worked fine.