Wednesday, December 18, 2013

Design choices

I have a quandary.

The Toast-R-Reflow controller works really well... so long as you don't want to change any of the parameters of the reflow cycle without uploading new firmware. About all the ATTiny85 can handle is letting you push "start" and displaying what it's up to. If Atmel (seriously, you have GOT to go check out their website right now. It's got pictures of SOIC and TQFP packages and calls them "stocking stuffers." LOL) were to make an ATTiny165 - that is, an 85 with 16 kB of flash instead of 8, then that would solve an awful lot of problems.

But, in principle, I don't have to use the ATTiny85. I could swap it out for a TQFP ATMega328. The price is $2.80 instead of $1.20 (in single unit quantities. Not that you'd buy them that way, but it makes for a valid comparison) - which doesn't break the bank, but it is more.

What do we get for our trouble?

Well, we get a whole bunch more pins, most of which we don't need.

However, we may be able to do away with the MCP23017 i2c GPIO chip to drive the display. The LCD would take most of the digital pins, but so what? That would make up for most of the cost difference (that chip is $1.44).

What we really get out of the deal is quadruple the flash. That should be more than enough for a parameter / curve editor UI. Perhaps even one that could handle multiple time/temp profiles.

I might have to consider that...

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