Fresh Eyes on serial communication

Projects Interfacing w/ Software on the Computer
1

I have a logic level convertor from sparkfun. http://www.sparkfun.com/products/8745
I have a RS232 convertor from SF. SparkFun RS232 Shifter Board Kit - PRT-00133 - SparkFun Electronics
I have arduino duo 5v and a Buffalo router with serial pins that run at 3.3v.

Using a simple sketch to echo whatever the arduino receives over serial

/*
* Reflect serial input back.
*/
int ledPin = 13;                 // LED connected to digital pin 13

void setup()
{
  Serial.begin(115200);
    pinMode(ledPin, OUTPUT);      
}

void loop()
{
   digitalWrite(ledPin, LOW);   // sets the LED on
  while (Serial.available() > 0) {
    Serial.write(Serial.read());
    Serial.write("blah");
     digitalWrite(ledPin, HIGH);   // sets the LED on
     delay(1000);
  }
}

Using arduino connected via usb using serial monitor my LED lights up and whatever I type is echoed.

Arduino -> RS232 board -> PC via putty I can light the led and get the reply from arduino.

Buffalo -> RS232 board -> PC I cancat < /dev/tts/0 and read whatever I type in putty.
From an SSH console on the router I can
echo blah > /dev/tts/0 and read it via putty on the PC

If I setup a test sketch in arduino that just does a serial.write("blah") or serial.printline("blah")

Then arduino -> Logic convertor -> router

Via SSH I can see arduino blah blah blah.

However I can not get my light to light and arduino to echo FROM the router via the logic convertor.

I think I have ruled out the RX/TX on the router and arduino as being problems as both work perfectly via RS232 board.
Whats annoying is that Arduino -> router works fine.
Its only router -> arduino that does squat.

I checked the voltage on the logic level convertor.
Its a solid 3.3v on the LV side and 5v on the HV side.

I have it hooked up:
routerRX -> LogicLevelConvertorTX1 -> TX0 -> ArduinoTX(pin1)
routerTX -> LogicLevelConvertorRX0 -> RX1 -> ArduinoRX(pin0)

I also tried this because I read that the RX paths arent bidirectional.
routerTX -> LogicLevelConvertorTX1 -> TX0 -> ArduinoTX(pin1)

anyway sorry its long but Im hoping Im missing something dumb here.

2

Did you forget that the router and Arduino should have their grounds connected ?

3

routerRX -> LogicLevelConvertorTX1 -> TX0 -> ArduinoTX(pin1)
routerTX -> LogicLevelConvertorRX0 -> RX1 -> ArduinoRX(pin0)

I think you have some directions backward.

First of all those are "I" and "O" for Input and Output, not 1 and 0 for One and Zero.

TXI (Transmit Input) is on the LV side (of both channels.)
RXO (Receive Output) is on the LV side (of both channels.)

You want to connect the 3.3v TX of the Router to a TXI input and the corresponding 5v TXO to Arduino RX.
You want to connect the 3.3v RX of the Router to an RXO output and the corresponding 5v RXI to the Arduino TX.

routerTX -> (TXI>LogicLevelConvertor>TX0) -> ArduinoRX(pin0)
routerRX <- (RXO<LogicLevelConvertor<RXI) <- ArduinoTX(pin1)

4

I think I had electronics blindness last night. I slowed down and hooked it up again like you posted and its working :wink:

I think I was also getting confused because of the sketch I was using.
I set it to turn on the LED and reply with Blah on any serial RX.
Well the router on boot and when "things happen" spews a bunch of text to serial. So arduino I guess filled its buffer and the LED stayed on and it kept saying blah over and over. It seemed locked up..
To compound the problem if the router serial gets a few inputs it pops up a login instead of just spewing text. So the arduino then replys with blah and a password of blah and the router pops the login prompt again. going into never ending loop and the LED staying lit and saying blah over and over. heh kind of funnny really.
I was able to see this all by putting RS232 board inline with the router TX.

Thanks for replying guys.