FlexBasic and quadrature decode

Mickster

I need to read six quadrature encoders (6-axis machine-tool) using FlexBasic on the P2.

I have been reading "Bob's Propeller P2 Guide" (HUGE) but it has only made my head spin

Is there a straightforward (simple) way for FlexBasic to nominate the 2 encoder-connected smartpins and to read/preset the count?

I realise that JM has a Spin object for this but can I do this directly within FB?

ManAtWork

Do you want a native Basic implementation for the quadrature counters (or even completely re-write JonnyMac's spin object in FlexBasic) or would it be sufficient to include the object as class in FlexBasic?

Mickster

I would prefer native in Basic, if possible. I don't need the detent, button, range-limit stuff. Also, I can read Basic

Ariba

Here is a simple example. I used a mechanical rotary encoder, which needs pullups. For a motor encoder this may not be necessary.

'' simple quad-encoder in BASIC
''
const _clkfreq = 160_000_000
const enc_a = 32                ' encoder A pin, B pin must be 1 higher

dim  encval as long

pinstart(enc_a, P_PLUS1_B + P_QUADRATURE + P_SCHMITT_A + P_HIGH_15K + P_OE, 0, 0)  'init encoder with pullups
pinhigh(enc_a)   'high for pullup
wrpin(enc_a+1, P_SCHMITT_A + P_HIGH_15K)   'B pin: only schmitt + pullup
pinhigh(enc_a+1)

direction(enc_a) = input        ' reset count to zero by toggling DIR bit 
direction(enc_a) = output

do
  encval = rdpin(enc_a)         ' read encoder
  print "encoder: ";encval
  pausems 500                   ' wait 1/2 second
loop

Andy

JonnyMac

My encoder object is fairly simple. If FlexBasic supports smart pins, it will be no trouble to translate. Keep in mind that you cannot preset the encoder value inside the pin. In my object I preset the value by resetting the encoder pin to 0, and putting my preset value into an offset.

pub set_value(preset) : result

'' Set encoder to preset value

  pinfloat(apin)                                                ' reset & clear
  pinlow(apin)                                                  ' re-enable

  preset := lolimit #> preset <# hilimit                        ' force into range

  result := offset := preset                                    ' set encoder value

I have range limits in the object for things like volume controls where you'd want to stay between 0..100. When reading the encoder, this come into play in the event we've gone past a defined limit.

pub value() : result

'' Return encoder value
'' -- returns encoder value turncated to lolimit..hilimit

  result := raw() + offset                                      ' read and update value

  if (result < lolimit)                                         ' limit range
    result := set_value(lolimit)
  elseif (result > hilimit)
    result := set_value(hilimit)

In the end I was able to duplicate my P1 encoder cog -- without using a cog!

Mickster

@Ariba

Holy moly....I wasn't expecting it to be this readable/understandable
Many, many thanks!!! I had to leave the shop and now I can't wait to get back

@JonnyMac

Thanks Jon. Yeah, offset is fine....being able to zero the counter is what I really need

Mickster

Became side-tracked with an emergency but now have 3 encoders hooked up

Smartpins totally ROCK!

Now I have another request that hopefully will be similarly elegant and self-explanatory. I'll start a new thread because on-topic titles might help future searchers.

aaaaaaaargh

@Ariba said:
pinstart(enc_a, P_PLUS1_B + P_QUADRATURE + P_SCHMITT_A + P_HIGH_15K + P_OE, 0, 0) 'init encoder with pullups

Hi, I can't find the Pinstart function in the flexbasic documentation. But the this code compiles fine. Are there more hidden functions?

Cheers

Mickster

Ditto:

I have several, similar queries but I am attempting to track down the solutions before asking....a FlexBasic thread/repository would be useful

Ariba

@aaaaaaaargh said:

@Ariba said:
pinstart(enc_a, P_PLUS1_B + P_QUADRATURE + P_SCHMITT_A + P_HIGH_15K + P_OE, 0, 0) 'init encoder with pullups

Hi, I can't find the Pinstart function in the flexbasic documentation. But the this code compiles fine. Are there more hidden functions?

Cheers

These are lowlevel pin access functions coming from SPIN2. It makes a lot of sense to use the same function/methode names as in Spin also for BASIC and C. (In C they need an underscore at begin).

The description of these functions can be found in the Parallax Spin2 document, together with the constant names. I've not looked into the flexBASIC documentation when I wrote that example, it was a translation from how I would write it in Spin, just with BASIC syntax.

Andy

JRoark

There are a BUNCH of C functions that just “magically” work in FlexBASIC. I know for a fact that most of the file IO calls work, as do many pin functions. There are probably more “undocumented” functions than there are documented functions. This seriously helps position FlexBASIC as a serious tool instead of a “toy” language. Many formal BASIC functions appear to be little more than just wrappers for underlying C functions. Play with them and see!