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You will find the PCB layout here: https://github.com/openenergymonitor/Hardware/tree/master/emonTxV2

Hi Robert,

I ask as I did my first pcb last week based on the emontx2 design but it only seems to work if I have SPI/ISP connected at the same time as FTDI, the FTDI alone and it fails to give serial output but it still functions ok

As far as I can see, the unused pads on the RFM12B are, how can I put it, unused - there's no connection to them! SDI, SDO & SCK are common to both the RFM12B and the SPI/ISP header, but the FTDI only shares data with the serial/I²C header.
I haven't got a bare emonTx V2 PCB to check.

Are you saying it's really a software problem and that you need something on the SPI port (presumably to do the handshake) for you to get serial output via the FTDI - programmer - USB - Arduino IDE?

I think I will do a video as it will make more sense.

I doubt that will help - I never look at videos! I'd much prefer it in words so that I can ponder over it.

I have used an emonTx V2 without the RFM12B, as an energy diverter, so I think your problem isn't in the ATMega 328P nor any of the usual software. That gives serial output quite happily via the FTDI - programmer - USB - Arduino IDE. I've never had occasion to use the SPI/ISP port.

I was wondering if the act of putting the programmer on the port caused a pin to go low/high.

hmm I cant see what I have missed, other than a gnd on the diagram on the xtal caps

Shouldn't pin 8 of the 328 also be grounded ? or is that just a diag error?

Well spotted and solves the problem.

Thank you both