Cheap Idea for a DRO

[BillTodd]

Hmm. -4v seems low, but if it works... I know I'm abusing the serial port, but I've used this circuit many times may be the prolific device is different to mine???

BTW are you driving it from a PC or laptop? (laptop USB ports seem to lack the ooomph required for most USB devices)


You could try sticking a 10u cap between the DTR line and Vss just to stiffen the -ve rail a bit.

Bill

[ecat]

More progress \o/

The sharp eyed would spot the problem in my previous post, I had no commas! That's right, every comma, 2Ch, was coming through as 0Ch which is form feed :( I tried reducing the collector resistance a little more and the comma appeared but so did the occasional funny in the rest of the message :( :(

A little reading showed me another trick, adding a resister between base and emitter is a common way to speed things up. 3k3 between b and e and things appear to be working beautifully :) :)

Hmm. -4v seems low, but if it works... I know I'm abusing the serial port, but I've used this circuit many times may be the prolific device is different to mine???

BTW are you driving it from a PC or laptop? (laptop USB ports seem to lack the ooomph required for most USB devices)


You could try sticking a 10u cap between the DTR line and Vss just to stiffen the -ve rail a bit.

Bill

Indeed Bill, -4v does look poor, not much margin for error. I'm connecting to a PC but via a powered hub. Another experiment perhaps.

The DTR line looks quite solid, at least it did before my latest changes, heh. A cap certainly wouldn't hurt, thanks for the tip.

As of now your PC app is mostly happy with the board. A couple of range errors when I simulate the calliper with a finger swipe but no data errors so far. Thanks again for your help :)