| ??? 09/20/04 18:52 Read: times |
#77741 - Alternative ISP software Responding to: ???'s previous message |
Thanks for your reply, Prahlad.
1. Pulling down D1 from printer port. Instead I will pull up with 10k. If the cable is disconnected I'd want the reset pin to not be in a reset state, i.e. low. Shouldn't I pull it down to ground to avoid a reset when the cable is disconnected? Obviously this circuit needs to be improved once the ISP is working and I'd have to incorporate a supervisor reset as well. But for now my only interest is in programming the part. 2. Using 74HCT573 [ Latch ] like a buffer with LE permanent High. I would use 74HCT541 instead. Certainly. I don't have access to 541 right now hence my use of the 573. Living in Mexico makes finding the right parts a hassle. 3. Pull down resistor on pin 9 [ RESET ] of micro is missing. Unlike Philips Atmel micros don't have an internal pull down on reset. If you want In System Programming and not In Programmer Programming put a pull down resistor. My thought was that if I'm pulling down D1 at the input to the latch then the output going to pin 9/RESET is already going to default to low if the cable isn't connected. Doesn't this eliminate the need for the pull-down resistor on pin 9? Given below is link to an excellent ISP programming software and schematic. I would suggest you to modify your hardware a bit [ Interchange LPT pins ] to suit this software and check that there is no hardware problem atleast. I stumbled on that ISP program/schematic but went with SP89 because it was open source and had a Linux version. I could try the above schematic but I'd like to avoid further hacking this parallel cable which is already a mess. As a last resort I can do this but I'd really prefer to figure out why the current design isn't working. Thanks again for your feedback. Regards, Craig Steiner |
