UIRT2 version A description

 

Features:

 

Circuit simplification:

If some features are not required the following components can be ommited:

 

 

Construction:

Place all components exept the crystal.

Perform the In Circuit Serial Programming:Remove Shunt1 and apply the programming voltage (12 - 14v) to the pin wich connects to R3.

I used the +12V from an unused hard disk header. 12V is on the low limit for the programming voltage but it has always worked for me, exept once but a second try was succesfull. Another possibility is to "raise" the 5V by connecting a 9V battery to the pins of Shunt1, the minus connects to the +5v pin, the positive to R3. This will create a VPP of 14V.

Replace Shunt1, mount the crystal and your UIRT2 should be working.