At90S1200 pic replacement

[Hubsy]

Hiya,
Grey Haired nooby question.

I've been in electronics for many years, too many years!!
Programmed Siemens industrial computers, so know something about programming.
Have designed and built more pcb's than I can remember.

I've just ordered the axe091 with usb cable. I like the look of the picaxe program, much simpler than assembler programming.

I've never used pics before, well not programming them.

My first project is to replace an Atmel AT90S1200 with a pic.
speed is not too critical.
3 inputs, possible one analouge.
3 outputs.

future projects will be connected with a model railway.

Which chip would you suggest I start with?

Thanks
Hubsy

 

[Andrew Cowan]

08M: 1 digital input, 4 pins that can be digital in, analogue in, or outputs.

14M: 3 digital inputs, 2 digital or analogue inputs, 6 outputs.

So maybe the 14M?

A

 

[SilentScreamer]

Look in manual one at the pin out diagrams, it will show you what each PICAXE is capable of (input/output wise). The 14M sounds good pin wise (look at appendix C (page 80) to see the full pin out), however it only has 256 bytes of program memory, doesn't the Atmel AT90S1200 have 1KB? Therefore the 18X might be better with 2KB of memory.

 

[hippy]

Some idea of what the program will need to do will help. It may be quite simple so any PICAXE with suitable I/O and ADC could work, if it's a quite complicated program it may need a PICAXE with larger program memory.

It may be that the task is not even within the PICAXE's capabilities, some PICAXE's may be better suited than others, perhaps any could be used, even the PICAXE-08.

My recommendations would be -

08M - for small footprint applications, and the AXE230 surface mount module is great for fitting in confined spaces.

14M/18M/20M - if you need more I/O than the 08M

18X - If you want a bigger program memory

28X1/40X1 - If you want even bigger program memory and more I/O

28X2/40X2 - If you want 'everything'

 

[eclectic]

@Hubsy
If you've got the AXE091, then it can be used with
three "running" chips.
Excellent for testing comms.

Perhaps then try

Socket 1. A 14M / 20M
Socket 2. An 18X
Socket 3. A 28X2

e

 

[MartinM57]

One strategy would be to develop on a 28X2/40X2 (strangely, the same price - and bang for buck, great value) using the minimum number of features you really need and then 'productionise' down to the minimum variant you need.

...but it's very hard not to keep adding features so that you end up productionising on a 28X2 or 40X2

There's nothing worse than buying say just 14Ms and then finding that late one night you need that one more crucial in or out pin and you wish you had a 28Xn to hand.

 

[hippy]

I agree with MartinM57 ( and not just to sell more X2's ! ). It can be very beneficial to develop first attempt and prototype code on an over-capable PICAXE before deciding which to use in a particular project.

I've previously recommended the 18X but it doesn't have the same ability the 08M/14M does to reverse I/O pins beween input and output which can be very useful in some applications. The X2's don't have that limitation.

There's no one size fits all approach to development. Sometimes you feel code will suit a smaller M part, sometimes know it won't, sometimes not sure, nor know where success in phase 1 will lead to, what more may be great to add.

Feature bloat or ending up with needing to use a more expensive chip because it's easier or better that way isn't necessarily a bad thing, especially for one-off and hobby projects. The extra cost is often not that much more, especially when the 'cost' of time and effort comes into the equation.

I'll be honest, and expect many here have felt the same, that they are determined to make their code fit the smallest, cheapeast PICAXE, and for good reasons - it's small, it's cheap and it's a challenge in itself. But I know I have, and I'm sure others have too, hit a wall of "Grrr!", where that has meant sacrificing something they'd have liked to add.

It's natural to want to go small and cheap, but not always the best path long term.

 

[boriz]

“built more pcb's than I can remember” – It’s the lead + flux fumes. They’ll get us all eventually

Welcome to the forum.

 

[Hubsy]

used an 18M

2* analouge inputs

2 switched input

servo output

3 leds

did ask the chap I'm making this for if he wanted it to play a tune, but he declind.


thanks for all your input guys.