Cannot get 1-Wire working

[ElevenOf9]

I'm working on a project where I need to read data from a DS2501 ROM chip but I'm having problems getting the Digispark to recognise any 1-Wire devices I connect. I've even tried running the 1-Wire Digispark example with a DS1802 connected but it only returns a temperature of 32F. I've got the chip's data line connected to pin 5 as-per the example. My code runs correctly on an Arduino, but not on the digispark, is there something I'm doing wrong, has anyone else had any success with 1-wire devices?

[digistump]

Did you put a pull-up between pin 5 and 5v? I'd suggest a 4.7k pull-up there.

Otherwise it sounds like it should work - with the pullup is how the temp shield is setup