Programming circuit revisited

[wapo54001]

While browsing recently on a well-known website (maybe P.H. Anderson or another respected Picaxe guru) I came across a link which took me to an interesting website where I read a discussion of the programming circuit. I've been looking but cannot now find this site.

Anyway, this well-experienced person had found that a 100K resistor from the Program In pin to ground is adequate to hold it low during operation, but also can be ignored while programming through the regular 10K/22K resistor network. In short, the 100K can be left in circuit all the time as the pulldown resistor, and doesn't prevent the chip from being programmed using the regular programming circuit.

Is anyone aware of which website I might have seen this information on? I'd like to go back and re-read the information.

 

[Andrew Cowan]

I don't know of the specific site, but Hippy's site has a wealth of information about nearly everything picaxe related.

Andrew

 

[wapo54001]

This site was on the end of a link included on one of the main Picaxe sites -- in a list called "useful links" or somesuch.

 

[hippy]

Could be one of the links here ... http://www.rev-ed.co.uk/picaxe

Even a 100K could be quite a divider once the input signal came through 22K, but it might work.

The solution I proposed was to drive the programming signal through two 74HC00 gates ( with its own 22K/10K input ) so the output drives the Serial In pin hard to +V or 0V and the resistance across Serial In to 0V becomes immaterial ( other than it'll sink current ). Almost any resistor would probably do. I'd go for 10K because there's less chance than 100K allowing noise into the pin.

 

[wapo54001]

I had a look at those links, no luck.

OK, I'm ready to try the 74HC00 solution. It'll be two weeks -- friend visiting from far away -- but I'll give it a try.

Hippy, have you got a schematic posted/squirreled away somewhere?