Joe's 1000x600x200 steel and aluminium router started

[devmonkey]

Interested to see how this goes. Glad to hear you're bit-banging, though as the 328 is inline with the axis pulses to the stepper drivers it has to keep up at all time (not just homing) and I'd be curious if you can hold the signalling whilst I2Cing the display - interesting challenge.

I did realise after writing that the optos were for homing switches/reflection into the DDCS, so, yeah, will be fine - I'll withdraw that.

Hi Doddy,

So it turns out if you ditch the standard I2C/TWI wire.h library and display driver, crack open the 328p datasheet, write your own crude framebuffer and I2C non-bocking state machine that operates directly on the TWI registers you can tick the state machine at a 2-3us per tick penalty. Will put it on the scope and see if this is sufficient.

Main loop becomes:
1. Mirror stepper/home signals with squaring logic.
2. Update framebuffer if needed (using a 5x7 font this is 5 memory reads/writes per character)
3. Tick I2C state machine.

I could remove the framebuffer to make it a bit faster if required, this will effectively amortise the font copy part at one byte/I2C tick.

Cheers, Joe

[Doddy]

Hi Doddy,
write your own crude framebuffer and I2C non-bocking state machine

"Crude"?, I prefer to think of this as "fit-for-purpose".

You know as well as I do the 328 is just one of a thousand different micro controllers that pollute the oceans and the Arduinio packaging is just a convenient way of throwing that chip into an accessible form for stupidly low cost - makes them a sensible solution for even the most simple of problems. There's no reason to use the Arduino libraries unless you're concerned about cross-platform compatibility or speed/ease of development (sacrificing code base, efficiency and real-time performance). I think you'd agree programming at the register level (I gave up at the instruction level many decades ago - I prefer to have a compiler at least) adds a level of complexity and care, but if that floats-your-boat (and it does, me) then hack away to your hearts content. At least you can be confident that you know exactly that the uC is behaving exactly as you want it to.