Inverting Smart Pin mode %01101

JimFouch2

Description from P2 Docs.... %01101 = Accumulate A-input positive edges with B-input supplying increment (B=1) or
decrement (B=0)


I'm looking at using this mode to keep track of the steps for a stepper motor controller.

Only issue is I don't see a way of inverting the logic for the B pin. Sometimes on an axes, I will want to invert the direction. I know the the simple way would just invert the sign on the reading of the smart pin, but that really only works if you start from zero.

When the device this is attached to hits it's home position, I normally load an offset into a counter. I then add whatever the hardware counter has detected. Without the ability to invert the B Pin logic, I think if I keep my offset separate from the SmartPin's output, I should be ok.

Tubular

Are you doing a wrpin to set up the B pin?

I remember OzProp telling me there are actually two ways to invert inputs in the WRpin config, I think you get a bit in the 'pin redirect' 4 bits, as well as a bit in the 'cio' field, and if you select both you're back to 'non inverted'. Fwiw

cgracey

In the WRPIN data, the top two nibbles select PINA and PINB inputs to the smart pins. The MSB of each nibble controls inversion. Is this what you need? This is from page 72 of the silicon documentation.

D/# = %AAAA_BBBB_FFF_PPPPPPPPPPPPP_TT_MMMMM_0

 %AAAA:  'A' input selector
             0xxx = true (default)
             1xxx = inverted
             x000 = this pin's read state (default)
             x001 = relative +1 pin's read state
             x010 = relative +2 pin's read state
             x011 = relative +3 pin's read state
             x100 = this pin's OUT bit from cogs
             x101 = relative -3 pin's read state
             x110 = relative -2 pin's read state
             x111 = relative -1 pin's read state

 %BBBB:  'B' input selector
             0xxx = true (default)
             1xxx = inverted
             x000 = this pin's read state (default)
             x001 = relative +1 pin's read state
             x010 = relative +2 pin's read state
             x011 = relative +3 pin's read state
             x100 = this pin's OUT bit from cogs
             x101 = relative -3 pin's read state
             x110 = relative -2 pin's read state
             x111 = relative -1 pin's read state

cgracey

You can also control inversion via the low-level pin configuration, which takes bits 8..20 in the WRPIN data.

In the logic mode %0000_CIOHHHLLL, the %I bit controls IN inversion.

Cluso99

Can you flip the inversion without upsetting any count in progress?

evanh

Cluso99 wrote: »

Can you flip the inversion without upsetting any count in progress?

For that smarpin mode, counting occurs on the rising A input. As long as A is not rising at the same time then inverting B will be clean.

JimFouch2

I guess I didn't read the docs close enough. Looks like this can be done easily.

Thanks Chip.

ManAtWork

cgracey wrote: »

You can also control inversion via the low-level pin configuration, which takes bits 8..20 in the WRPIN data.

In the logic mode %0000_CIOHHHLLL, the %I bit controls IN inversion.

Every time when that table is referenced somewhere it should also be noted that nobody has to learn any of the bit patterns, theese days. There are predefined symbols that can be used to make everything much easier. See end of Spin2 documentation Chapter "Built-In Symbols for Smart Pins".