How to physically Programme the MK2 PVrouter

Hi I bought emonTX v3 and Robin Emly’s Mk2 Router about 7 years ago and I must say first off that they both have worked non stop ever since and I am mightily impressed with both of them.
I now want to update the firmware on the Mk2 router to be able to take two loads as I am still generating more power than I can use in the daytime.
I don’t know if it’s my age but for the life of me I can’t remember how I did it.
I know I used a USB programmer and I think it was connected to the emonTx.?
Can anyone help or point me to any instructions please?

All you need is on Robin’s website: https://www.mk2pvrouter.co.uk

The Mk2 router is NOT an emonTx, but t uses the same processor, hence you program it in exactly the same way. You’ll need the Arduino IDE installed on your computer and you’ll need a USB to FTDI Programmer (which you presumably still have, if not, Robin will sell you one, so will The Shop here).

Thanks Robert
I do have Both the EmonTx and the PvRouter ! I had a modification to the PvRouter done to read Diverted power Data to the EmonTx .
Having just remembered that! I think i’ll have to ask Robin directly as I think I might have adapted software.
Thanks again
Mike