Arduino Mega/ LCD/ MAX233/ RS232 circuit problems

Hey folks…

I got a new Arduino Mega and it is connected with my screen.
Now I want to read a signal from a scale: Information scale: baudrate is 9600 bps, ASCII, rs232, 12V.
I tried to connect it with a MAX233 to my Arduino Mega. Unfortenatly I am completly new with this stuff and I have big problems with the connection. I do not know how to connect it correct. I found different ways. But none is working. Furhter, maybe my code is totally wrong.

Attached my code.

I am looking forward to hearing some examples. Thanks for your efforts.

#include <LiquidCrystal.h>

LiquidCrystal lcd(22, 23, 24, 25, 26, 27);
float incommingByte = 0;

void setup(){

void loop(){
if (Serial1.available() > 0){
incommingByte =;
Serial1.print(incommingByte, DEC);

You are trying to do too much all at once. Break your project up and check out each part separately.


I'm not sure what is wrong, is it that you can't get the Max233 to work? Or that you can't get the Arduino to read the messages? How about the LCD? What are you trying to do?

I really can't make out what is your problem to begin with. You could post a schematic of what you done so far?

Thanks for the answers...

My screen is working. My MAX is working too. I checked the voltages and they are as I excepted. My problem is that the board is not reading the value correctly. I get a signal but the board is reading some wiered stuff. I do not know if I have a problem with my code? Should it work the way it is?

Thank you for your help.

I believe the ArduinoMEGA has a extra pair of Rx and Tx pins. Which pins you have connected to which pins on the Max233?

Also, do you have all pins correctly connected on the Max233, I usually use the Max233A to avoid using caps...Could you tell me what you have connected to the Max233?

I assume you are trying to use communication pin 3 and 4 (Arduino1280 pin 19 and 18) this so?