Mark Rages wrote: > On 9/27/06, Roy wrote: >> Let me know why this would not work :-)) > But when Target tries to change and go high, it will be pulling > directly against the transistor in U1. Ouch! You'll probably find that making a bidirectional isolated interface is not trivial :) You need a mechanism to disable the active drive of something like U1 when its input (in this case the diode in U1) is not actively driven by the associated signal (AVRDragon in this case). Gerhard -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist