@rb550f Tested 8ch card similar to yours.no problem am I correct in saying a digital " on " switches on relay but relay remains energised by digital " off " ,until you disconnect port

@Bravia, that seems correct. @rb550f cannot get the relay to release with the "digital off" command and must disconnect the port to release the relay.

If that the case I would check the supply voltage to the relay card mine is around 5 volt and make sure both grounds are connected.

I cannot see how a digital off would give a voltage to energise relay

@rb550f do you have a link for that converter? That looks like a great way to solve my issues also.

Here is a LINK to a board that I use for converting TX, Rx levels between the EZB(4) UART0 and the Roomba R3 model TTL port.

The digital outputs of the Ez-b v4 are different from the digital outputs of the ez-b v3.
according to the spec sheet ez-b v3 digital outputs are rated

Digital I/O High-Current Sink. - 25 mA Digital I/O High-Current Source - 25 mA Digital ports can output low current +5 or GND to power LED’s or communicate with peripherals.

The ez-b v4 digital outputs are rated

330 ohm current limiting Resistors on each Digital I/O pin

Digital I/O TTL Voltage Level (output) 3.3VDC

Can't find a sink and source current in the EZ-B v4 spec, but like the digital output high voltage the digital output source and sink current are probably different as well.

The ez-b v4 digital outputs are having trouble meeting the input requirements of the relay board.