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

[pedja089]

I was thinking that 1 is represented with missing pulse.
You can try something like this

DEFINE PULSIN_MAX 65535 ' Limit wait-for-pulse and maximum-pulse count
While PORTC.4=0 'wait for rising edge of start pulse
WEND
FOR I=0 TO 33
PULSIN PORTC.4,0,W3
IF W3>XXX THEN GOTO GotData
NEXT I

[CuriousOne]

A side note, a statement like

IF PORTC.4=1 THEN

actually sets PORTC.4 high.

Is this bug or feature?

I've added 1 transistor signal inverter, but no help. Also, your code does not work.

OK, I will give up with this idea.

[Heckler]

This, to me, is the classic problem of how to tell (program) your micro controller to recognize and interpret the pattern.
The human brain combined with an eyeball can recognize it... now you just need to figure out how to translate that into code.

I would start by watching for the start pulse, which is longer than the other pulses. Then keep track of the width of the following pulses (or the width of the "low" part. Then watch for one or more extended "low" pulses.

Since you only need to differentiate between 0 and any other number/key press, then just watch for an extended "low" in a given time period after the extended "high" start pulse. If in the given time period you do not get any extended "low" pulses then the digit is "0" other wise if you get an extended "low" pulse then the keypress was non-zero.

Since the quantity of pulses in each character is always 34 then you should be able to just set up a counter to increment whenever the pulse is low and stop incrementing when the pulse goes back high. Then if the counter has incremented above a certain threshold then that particular "low" pulse was a "wide" one and indicates a non zero digit. (I hope that makes sense)

I believe it is easily do-able. you just need to distill it down to how to detect the extended low pulse that indicates a non-zero digit pressed.

that is how I would attack the challenge.

[pedja089]

Code for that is in post #11 except it waits for transition from low to high to start measure 34 low intervals.

[CuriousOne]

Yes, I know how to implement detection logically, I have no issues with algorithm, but I can't implement it in hardware, also, I can't understand, why statement
IF PORTC.4=1

or

IF PORTC.4=0

makes corresponding pin high or low?

[tumbleweed]

IF PORTC.4=1
or
IF PORTC.4=0

makes corresponding pin high or low?

I highly doubt that. I don't know how you're testing it, but if that's the case things are seriously broken.

You likely have some other issue.

[HenrikOlsson]

The IF statement per se should not and I'm pretty sure does not twiddle the pin but if what you you're doing is somehing like...

If PortC.4 = 0 THEN
   PortC.1 = 1
ENDIF

...and there happens to be analog functions on the pins which you haven't disabled then the actual state of PortC.4 isn't read correctly and you're getting into the classic RMW issue where the "invalid" state of PortC.4 is being written back to PortC.4 when the write operation to PortC.1 occurs but without seeing the rest of the code it's hard to say for sure.

/Henrik.