Is it possible to interpret non-standard serial data with PicBasic (sample attached)

[Art]

Easy! It’s giving you a wider pulse duration at the start to qualify the incoming data.
From there you only need to sample 32 times at the correct interval.
So look for that, then read it in with a 32 step loop.

bitcode var byte[32]
count var byte
pulseduration var byte

pulseduration = time from peak to peak

for count = 0 to 31
bitcode[count] = inputpin
pause pulseduration
next count

Of course, better ways than reading into a 32 byte array, but quickest.

[CuriousOne]

You're omitting an important thing - MCU has own clock, wastes different time on program execution, but incoming data is sent async, so it can't wait for MCU to become ready, so my guess, how it all should work, is as follows:

As pulse arrives, we start recording it as fast as possible, after pulse sequence finished, we just count numbers of 1's and 0's recorded, and based on that, decide what to do with decoded data. Considering total sequence duration and speed, I guess, external sram or eeprom might be needed?

[Art]

That depends. You didn’t display the duration.
If it’s several uS duration pulses, the falling edge of the first longer pulse is the place to mark time,
then waste half a pulse duration before the for-next loop. If you can roughly synchronise from the first pulse (which is what it’s for),
it takes time for the two clocks to drift apart.

If you were to sample bits as fast as you can, you’d still want to do that from the falling edge of the first pulse.

[Art]

Does your hardware have the LCD that is in your code?

[Art]

That should get the 32 bits straight into a four byte array.

'
main:
@ clrwdt
'
if portc.4 = 1 then	‘ count initial pulse duration
leadcnt = leadcnt + 1
else
leadcnt = 0
endif
'
'
if leadcnt > expectedduration then' qualify initial pulse duration
burst:			' sync to initial pulse falling edge
if portc.4 = 1 then
@ clrwdt
goto burst
endif
'
for rotcnta = 0 to 3	' shift data into 32 bit buffer
databuffer = 0
for rotcntb = 0 to 7	‘ shift data to each byte
databuffer.bit0 = portc.4
databuffer = databuffer << 1
dataarray[rotcnta] = databuffer
pauseus peaktopeakduration
next rotcntb
next rotcnta
‘
leadcnt = 0
endif
'
goto main
‘

[richard]

surely a candidate for timer1 and gate control

[CuriousOne]

Currently I have LCD connected, for debugging purposes, but in final device, I will have no LCD.

[CuriousOne]

So this is how initial things should work, as I see it:

1. We sent interrupt on rising edge of PORTC.4
2. As PORTC.4 gets high, timer is started, and counts to predefined value (width of 1st pulse)
3. While timer is running, PORTC.4 is still being continuously checked, to determine, whenever it is still high. It should be high while timer is counting, if it gets low, while timer is on, this means, this is not proper pulse, so we should reset and start everything over.
4. If timer counting ended, and PORTC.4 was high all that time, this means that sync pulse was captured correctly, and we're ready for the next step.

This appears quite simple in words, but all Greek for me, in code , so far, my practical experience with timers and pwm is light dimming, and playing polyphonic tunes via it

[Ioannis]

Or Timer1 and Interrupt on Change or even better Interrupt on PortB.0 and use of Option_reg.6 to select which edge is expected to arrive and trigger the interrupt.

Needs a bit of work in the interrupt routine...

Ioannis