Please tell me there is another version of this coming out, why doesn't this thing have the capability of on-board programming like the rest of the shields do? You literally have to take the shield off to program the Arduino and it becomes such a hassle when you are debugging software and not only that, you are making the connector terminals wider. Does anyone know of a way I can rig it up so I can wire the board up to not do this?

*UPDATE: So I figured out how to use this thing to its full potential without interrupting anything with the main serial communication between your computer and the Arduino. So in order to achieve this, you will need a Arduino Mega 2560 because the uno doesn't have this feature. So since the Mega has multiple serial communication slots for serial 1,2, and 3, you have to bend both the Rx and Tx pins 90 degrees so that they don't go into the Rx0 and Tx0 lines and then just jumper wire the Tx and Rx lines from either Serial 1, 2, or 3 pins so that it uses a different serial Rx and Tx so it doesn't interrupt the function of the I/O and communication from the Arduino to the computer. I already tested this and works great now. You can also program the Arduino while the shield is on the Arduino, so you don't have to keep taking it off and on. If anyone has any questions how to achieve this, I will post a instructional download so everyone can do this with pictures.

I recently purchased two of these, and have had success. However, success didn't come without a few pains. I did get communication between two Uno boards - after I connected their grounds together, as most info mentions. Use the standard 'Serial. xxxx' commands. This board uses the hardware serial (pins 0,1), not software serial. In the fine print you'll find that you can not program the Uno with the USB connection without first removing this shield - trust me, it won't work. I now use jumper wires to connect to the Uno so I can quickly disconnect pins 0&1 to program it. The second 'pain', is the error on the Schematic. I wanted to use the DB9 connector, since it has a ground. However, it does not. There is no connection from ground to any of the DB9 pins. I soldered in a jumper wire to correct this. Additionally, the schematic says the data lines are pins 2 and 3. Pin 3 is line B, but line A is on pin 4. Nothing is on pin 2. I was finally able to communicate with an industrial device, and got good data back. UPDATE: The "error" on the schematic is only half an error. The assumption is that you'll be using a female DB9. I was using a male, and so the pins occur in reverse order. I should not have made the assumption...

Any one have any code that runs on this? I cant seem to get it to respond. May be a transceiver issue.

I'm looking at the schematic. I don't believe they got the transceiver control right, you don't just connect the TX data line to the enable line (via an inverter in this case). The RPi version seems to have the same flaw. The transmitter should be enabled for both 0 and 1 bits.

This may work in some cases, but it's way out of spec.

Hi all This shield is compatible with Arduino YUN? I have to use it for Modbus RTU.

Please provide a RS422 version with jumpers to enable the Rx/Tx pins so those can be wired to whatever pins you choose to use as the UART.

Oh, and both RS485 and RS422 require a common ground reference. I used to think they did not, but upon further reading I found it is needed. So providing a ground terminal would be a good thing even if you don't make a RS422 version.

Hello, could anyone provide me a programming tutorial for Arduino Mega 2560? I would use this Shield with these PING sensors: http://www.dfrobot.com/wiki/index.php/URM04_V2.0_(SKU:SEN0002)

Could anyone please point me in the direction of a good tutorial using this board and a Modbus library. I have been trying to go through the examples from http://code.google.com/p/simple-modbus/ and http://playground.arduino.cc/Code/ModbusMaster but with no luck. I am trying to retrieve information from a modbus slave being a Schneider PM5110 Power meter.

This shield is compatible with Profibus DP protocol?

It would be very good

I am looking to create a simple controller for a BlackMagic Studio Pro Recorder which runs on the RS-422 protocol, does anyone know if this can be converted to RS-422. This only needs limited functionality for our purposes, We all looking to create a controller that will start recording and stop recording and provide the feed back signal so we know if we are recording before a launch.

This only drives to rs485 bus for one state of the transmit data. It won't work unless somewhere else on the rs485 bus it is biased so the other state is the default. And forget about high speed or long lines. I expected better from Sparkfun... Wouldn't be hard to wire the driver enable to another pin of the arduino. Most other designs I have seen use digital pin 2. At least one (mentioned below) uses a retriggerable timer circuit so specific code to control the transmit enable line isn't needed.

Is there a library for Arduino? Or how does one program this things?

How many such shields can you stack on an Arduino. Each shield is just for one serial port right? So if I need to use all 4 ports of Mega 2560 do I need to stack 4 of these shields onto it?

This would be nice to use for making an Arduino based Modbus master device to query a Modbus power meter, shouldn't be to hard to do - right ?

how many wires you need if you want also to send the power supply to another arduino/rs485 shield?

I much prefer my design: http://eco-sustain.org/2013/06/14/testing-version-2-of-the-rs-485-shield/

Although it works for the 3.3V, it can easily be modified for 5V.

I believe that 485 is the protocol that dmx512 is based upon, which would be lighting controllers and the like for music and theatre and the like....

I use RS485 for robotic systems. this allows the different boards communicate over the entire robot w/ reduced chance of noise issues. I think they should have full and half duplex.

These shields scream for prototype areas.

My only complaint on this as well as the Cute-digi RS485 shields is that they don't have a screw terminal for shield/ground. I have on more than one occasion had equipment that refuses to work without it. Otherwise they work great for industrial equipment and and the Modbus-Master library in particular. It should also be noted that RS485 works great in high noise environments, like those around VFD (variable frequency drive) applications. It would also be nice to see a jumper selectable terminating resistor for those really long runs.

4000ft! cool.