
About same price - this is the one I bought So I took Will's advice and bought an RS-232 shield - not the exact DFRobot one he has but one like it that has RS232 but also RS485 option. The RS232 board was my biggest source of frustration earlier - I was trying to use the $2 RS232 to converters and nothing would work - spent way too many hours messing with it. of Midnite Classic Modbus register document īut I also have a Mega for future projects Pin 5 - not used ( though I had connected solid orange of Cat 6 to it ) Pin 4 - RX input ( I used white/blue of cat 6) this goes to Pin 3 of DB9 which is Transmit Data Pin 3 - TX output ( I used solid blue of cat 6) this goes to pin Pin 2 of the DB9 which is Receive Data Pin 2 - ground ( I used the white/orange wire of cat 6) this goes to pin 5 ground of Male DB9 connector It is plugged into the lowest bottom jack of the Classic ( labeled Master In on Classic) I put an RJ 11 connector on the Classic end - it only had 4 contacts instead of 6 but it plugs in and works because pins 1 and 6 are not used for the modbus anyway. I ran a piece of Cat 6 cable that I had here - about 22 feet or so I think. I deleted all my old posts where nothing was working the way I was doing it previously. I think you are not to far away from being successful. empty, Red (4), Green (3), emptyĪ common error is to connect RXD to RXD and TXD to TXD instead of RXD to TXD and TXD to RXD. Lower row of pins: Left to right - Yellow (2). Lower row of the five pins in the DB9 connector shown Slave RXD: pin4 green 4 red 4 Pin2 Master TXDīOB Male DB9 pins order which connect to Shield female sockets.

Slave TXD: pin3 brown 3 green 3 Pin 3 Master RXD Slave gnd: pin 2 red 2 yellow 2 pin 5 Master Gnd The logic does show how I followed my pinout through the system. Remember: Arduino is master, Classic is slave.

Midnite data shows TX pin 3 and RX pin 4.

GND is pin 2, RX is pin 3 and TX is pin 4. I use the lower RJ 11 jack as I have a remote MNGP connectted to the middle. Please be aware that in the Midnite document Midnite Solar MODBUS Network Spec Rev B.3 the pinout for the lower RJ11 port is NOT correct.
