Go Down

Topic: RX/TX Not working on breadboard (Read 364 times) previous topic - next topic

korstiaan

Hi,

First I've made a circuit/program on a UNO R3 board where I connect a MAX483 to RX/TX of the UNO. Everything works fine and super fast. Then I rebuild everything on a breadboard. Now I can send and I receive my answer once but thereafter it only answers now and then.
Therefore my .NET program and the sketch get time-out.
I tried everything (adding resistors in the RX/TX line, and parallel with RX/TX) but with no results.
And now it comes: I can get it working on the breadboard by ALSO connecting these RX/TX lines to the NOT WORKING UNO board????
Strange because the UNO board at that moment IS NOT powered (not by the power socket and NOT via USB) and even has NO 328P installed ???????
So it seems there is something that I need to add (capacitor? resistor? how? why?, ...) or is it the boot loader?
Since I get it working by connecting the TX/RX also to the UNO, it has nothing to do with the RS485 link. (120 ohm terminated)

Please help?

Korstiaan

Grumpy_Mike

It is confusing asto what you connect to what that works an what dosn't.
A diagram would help a lot.

korstiaan

On a breadboard, the pin 2 (rx) of the 328p is connected to pin 1 of the max483 (ro). Pin 3 (tx) of the 328p is connected to pin 4 of the max483(di). The pins 2-3 of the max483 are connected to pin 4 of the 328p to control the direction ( half duplex...).
In the meantime i've just got it running but I don't know why and if it will be stable: I have connected 2 capacitors of 10nF . 1 between the rx and ground and 1 between tx and ground.
Is this the definitive solution? Why?

Go Up