newbie question rs232

Forum 2005-2010 (read only) Hardware Interfacing
#1

Hi there My brother and I have in our possesion serial lcds (actually ten of them!) from Milford and we are having trouble using such an lcd with arduino.

the very helpfull support of milford wrote to us about the serial controller : '' It will receive data as RS232 format I.E. inverted, at RS232 0/9v or TTL 0/5volt levels. If you have any problems with sending data please check that the output voltage from the Arduino module is at least 4.5 vdc for the logic input, and is being sent RS232 8N1 @ 9600 baud or 2400 baud if the jumper is removed. ''

Can you please suggest a way on how to do it?

I am newbie and I am a bit lost and since we have 10 lcds it would be a waste not to use them!

#2

or TTL 0/5volt levels.

That is the clue. That means it is OK to connect it directly to the arduino. Find out how you change to this option, is it a different pin or is there a link to swap over.
Also find out the baud rate the LCD requires.
You can then use the built in hardware to drive the LCDs or use the software serial library. The latter is probably the best as you can use more than one output and it doesn’t interfere with the downloading / debugging process, using the single hardware would.
Note you do not need the LCD library to drive this but you do need to find out what commands to sent it.

#3

thank you for your reply
unfortunatelly I have two more questions:

  1. ‘’

You can then use the built in hardware to drive the LEDs

‘’

what do you mean?the LED part confuses me…shouldn’t I use the TX pin?

  1. on the LCD manual it says
    ‘‘Instructions to the LCD must be prefixed by the single byte <254> which will put the LCD into Instruction mode. The LCD automatically reverts to Display mode once an instruction is received. The LCD will accept all the common control codes. To differentiate between control codes and normal characters the LCD must first be sent the code 254. To clear the LCD screen therefore (control code 1):
    SEROUT 0,N2400,(254,1)’’

that is an example of basic…how do I do it with arduino?

is Serial.print (254,1) correct?

#4

I think you need to use Serial.print(254, DEC) and Serial.print(1, DEC).

#5

the LED part confuses me

Yes sorry a slip of the keyboard, I have corrected the original.

I think you need to use Serial.print(254, DEC) and Serial.print(1, DEC).

No that will give you lots of characters you want to just send the bit pattern. You want to use:- serial.write(254);

#6

Ah right, using the DEC converts it to a c-style string before sending, where you only need one character.

That makes me wonder whether "\xfe\x01" works too. (instead of 2 calls)

EDIT: To clarify, I'm worried about the trailing 0.

#7