Serial devices with UNO

Forum 2005-2010 (read only) Hardware Interfacing
1

I'm new to all this, i bought my uno last week and so far it's been great.

I'm working on a project where I need the arduino to send sensor values via serial to a PC and also print to one of those thermal printers which also needs to be via serial.

I see that only the mega has multiple serial ports that can communicate at different baud rates.

But, I was wondering if there might be a way for the uno to send serial data over the USB to the PC and also send serial data to the printer over digital pin 1.

Hope the question is not too stupid. :stuck_out_tongue:

thanks!

best,
mk

2

No. But there are serial software libraries available that will allow you to communicate to your printer on any other pins and at any other baud rate. Best to leave the hardware serial function dedicated to the USB connection and use software for other serial devices. Of course as you stated the mega boards have four hardware serial ports available for use.

http://arduiniana.org/libraries/newsoftserial/

Lefty

3

But, I was wondering if there might be a way for the uno to send serial data over the USB to the PC and also send serial data to the printer over digital pin 1.

Yes, but ... :slight_smile:

Digital outputs can drive more than one digital input. You can hook up the printer to pin 1 (you'll probably need something like a MAX232 to produce RS-232 signal levels), and have the serial output go to both the printer and the PC. Your PC software will have to be smart enough to ignore the printer output coming back at it.

But you're probably better off following retrolefty's suggestion and using SoftwareSerial to send the data to the printer.

4

Thanks for the help.

SoftwareSerial seems like the perfect solution but looking into it, it seems that other pins can only send data at 9600 and the printer i'm using needs 19200 bauds.

neither my pc soft or I are smart enough to separate serial output values.

should i just get a Mega? :cry:

5

That NewSoftSerial library link I posted earlier has many more baud rate choices, including 19200. Extract from the source code:

void NewSoftSerial::begin(long speed)
{
  _txDelta = 0;
  switch (speed) 
  {
  case 115200: // For xmit -only-!
    _bitDelay = 8; break;
  case 57600:
    _txDelta = -3;
    _bitDelay = 31; break;
  case 38400:
    _txDelta = -3;
    _bitDelay = 51; break; 
  case 31250:
    _bitDelay = 62; break;
  case 28800:
    _txDelta = -4;
    _bitDelay = 70; break;
  case 19200:
    _bitDelay = 108; break;
  case 14400:
    _bitDelay = 152; break;
  case 9600:
    _bitDelay = 226; break;
  case 4800:
    _bitDelay = 464; break;
  case 2400:
    _bitDelay = 940; break;
  case 1200:
    _bitDelay = 1868; break;
  case 300:
    _bitDelay = 7436; break;
  default:
    _bitDelay = 0;
  }

Lefty

6

nice! I guess I overlooked that.

i'm waiting for my parts to arrive. As soon as I have them i'll give it a shot with NewSoftSerial and let you know how it goes.

thanks again!