Need to pick someones brain about a Real Time OS setup on an embedded processor. Flash/SRAM sizes, C or java for apps, and general genning up on this stuff.
Can anyone help?
Guess who! 
OK embedded linux, busybox :nod: http://www.busybox.net/
How much stuff in the box? well it depends on the app, 128 meg flash should be plenty,
Code in ‘C’ small and tight. Read java heavy and resource thirsty.
Tell me more about what you are trying to do.
OK, we’re working out the mips requirement now, but something like a moto 68*** is what we’re thinking. It needs to be cheap so 128Mb is WAY too much. Looking for something like 2Mb flash, 8Mb SRAM max due to cost requirements, then of course that has to be able to be big enough for the apps too. It’s a RT control system.
OK so you are not just looking at a little linux but really tiny tiny linux. Basicly you will need to find all the drivers you need and compile them into a base kernel along with the realtime extensions. The application will need to be written in ‘C’ and staticly linked. You will probably need to setup a cross complier environment and have a development board that is a bit bigger than finished product so you can “watch” the application run. Stay away from big libs (like stdio) on the compile as they tend to have lots of stuff cramed into them. Ususaly the board manufacturer can explain a development environment. Usually a PC with a I/O connection to the testbed (serial, net, USB) .
A couple of questions:
- How much are you going to spend on a base system? base cost estimates?
- what kind of I/O do you need to do? A/D? D/A?
- does your code need to be interupt driven? or will polling work?
IF you base board cost could go up a little a mini PC industrial computer running something like a NS Geode CPU, your development effort goes way down, the boards are generally very I/O rich, usually have a place for Flash card plugin (so development env can be big and you just strip it down for normal) and can run standard X86 stuff.
http://www.bvm-store.com/ProductDetail.asp?fdProductId=49 under 200 quid.
A) £50
B) Not defined yet but all interfaces are digital
C) Probably interrupt, but again it’s still in the development phase.
For the price we’re going to have to build our own system, as all the mini PC stuff is too expensive and have shed loads of stuff we don’t need.
What kinda size linux for C compiler, Ethernet, USB, WiFi interfaces you reckon?
EDIT: Done anything with Tiny OS? http://webs.cs.berkeley.edu/tos/ seems setup just for this kinda thing.
Well usually how it goes is you find the lean mean kernel, (prolly based on 2.0) and then add into it the device drivers you need. The compliation takes place on a cross compilier platform like a PC with the proper execution units. You can actually start to find out the ultimate size at that point and get you final hardware environment designed around it.
TinyOS might be just the trick with what you are trying to do.