I recently bought an RS485 shield and am having lots of problems with stability when more than 2 devices (One Mater and one slave)
http://arduinoinaustralia.com.au/products/rs485-shield-1
Can any one help and confirm from the schematic that the shield has the 120 ohm termination resistor fitted internally and that the 4.7k pull up/down resistors shown on A and B are also internally installed?
If anyone else has one of these shields I would love to hear from you.
I don’t have one.
yes, the schematic has a 120 ohm resistor across A and B, with the label R6,
the photographs and mock ups show resistors on the board that are probably R3, R5, R6, R7 and R8,
you’d best check with multimeter in resistance mode across A and B, with the board unpowered, to quickly verify the resistor R6 is present,
otherwise you should probe around with a multimeter to identify each resistor near the A and B pins of the large green screw terminal connector.
