below (search for zzzz) are BOTH uncommented then the upload hangs on Uploading to I/O board and then hangs the usb/serial port until the EtherMega is reset (using the button). This codes works perfectly on Ethertens. On EtherMega, If I let in only ONE of those lines, either one, no issue, uploading completes fine. I am using a separate DC supply on the EtherMega, as per your advice on the Freetronics site, but that makes no difference. This issue is repeatable. Below is the whole code so far. Using IDE 0023. Can't get my head around changes required for 1.0 so I'll stick to 0023. This code I've modified from other sources (inc Jons as well) and which has been running since December on a couple of EtherTens without issue, with the commented zzzz lines in service. The resultant device EtherTen + RTC + SD Card + DHT22 logs temperature and humidity at timed intervals, logs it to the SD card in a filename of the date YYMMDD.csv and also hosts a web page with the current time, date, temperature and humidity and also shows all the log files on the SD card and allows you to open/save the log files via the web interface. I wanted to extend this and include DHCP or SD card loaded Network configuration, web modifiable IP Address and time/date, but this is currently at the edge of the memory available in the EtherTen, so I bought a EtherMega..... I'm onto my 2nd EtherMega as