----- Original Message ----- From: "drmail377" > > I looked at Guido's parallel port interface, it seems prone to ground > loops. I would use high-speed opto-isolators with logic-level > interfaces (from NEC perhaps) or maybe a voltage translator (NXP > GTL2002 perhaps). >
I would think you would need a massive ground loop to affect the TTL LPT signals! A Softrock would not work under those circumstances. Ground loops can be eliminated by breaking the ground from the parallel port. The only problem I have had using Guido's simple interface is when I attempted to decouple the I2C connections. (When using 120 feet of cable on them! Works OK with no decoupling though I've not tried when TXing.) I can not see that RF from the Si570 would affect it either, unless you connected the output to the I2C lines. Don't forget the I2C needs clean pulses, any capacitance to ground will affect that. 73 Alan G4ZFQ
