Hi there,
I am having an issue with an RS232 device connected to my Arduino Mega 2560.
When I try to read it I have no issues.
But when I try to send a message it does not work.
It comes from the fact that it needs a differential input.
Do you know if there is a solution to make my Arduino Mega 2560 using [-5V, 5V] instead of [0,5V] for one TX pin.
Thank you very much.
Taz
The mega doesn't accept RS232 . It accepts TTL RS232. (GOOGLE TTL) (GOOGLE RS232)
(which by the way is NOT differential ,but bipolar. RS485 is differential but that is not related to your question. You need a MAX232 chip or an RS232 to TTL serial converter .(google it). Normally I would provide links but you should have already realized the Mega doesn't have RS232 (if you looked at the specs)
You need a TTL to RS232 serial adapter to invert the signal and provide negative voltages. This one works well.
RS-232 is not differential, but it's bipolar (it swings positive and negative). RS-422 and RS-485 are differential.
I am having an issue with an RS232 device connected to my Arduino Mega 2560.
It's customary (on this forum) to be specific when describing hardware, specifically WHAT RS232 device (please post link).
Also, do you see RS232 listed here ?
Technical specs
Microcontroller ATmega2560
Operating Voltage 5V
Input Voltage (recommended) 7-12V
Input Voltage (limit) 6-20V
Digital I/O Pins 54 (of which 15 provide PWM output)
Analog Input Pins 16
DC Current per I/O Pin 20 mA
DC Current for 3.3V Pin 50 mA
Flash Memory 256 KB of which 8 KB used by bootloader
SRAM 8 KB
EEPROM 4 KB
Clock Speed 16 MHz
Length 101.52 mm
Width 53.3 mm
Weight 37 g
Do you know what RS232 is ? (have you ever heard of it before ? used it ? etc...)
I only ask because you didn't begin your post with "I have a mega2560 and want to connect to an RS232 device (don't know jack about RS232)"
Alternative rs232/TTL conversion circuits.
http://www.scienceprog.com/alternatives-of-max232-in-low-budget-projects/
Now that is a damn useful link ! After all, you can never have too many alternatives to RS232.
I always keep a couple of 2N2222 and 2N2907 transistors in my pocket, you know , just in case.
I like the gates method too. Who doesn't have a ton of CMOS chips left over from the "good ole days ". I actually sent that link to my email.
Who can't afford this ?
10 cent zener diode
Thanks all of you for your help.
I am going to order a TTL to RS232 Converver.