Help with serin, serout, Manchester encoding

[skimask]

The following also works. Assuming a 4 bit nibble is to be sent, build a character of start bit, 8 data bits and one or preferably 2 or more stop bits. Use Char_Pacing to get extra stop bits.
Brian

I agree with your strategy almost 100% ('cept I use lookup/lookdown tables).
But about the Char_Pacing above...
If the Char_Pacing value is too large (over a few of ms, 5ms for the TX/RX modules I use according to the spec's), the data slicer will lose it's mind and basically every byte will need a preamble.

[BrianT]

You are correct that setting Char_Pacing too long will defeat the purpose. The reason for adding an extra one or two stop bits is to prevent the problem where the SERIN software UART can misframe on a repetitive pattern and what it takes for the start bit may well be bit 3, 4, 5, etc. By giving the system 2 or 3 stop bits the SERIN command will fall into sync in just a couple of characters.

HTH
Brian

[skimask]

You are correct that setting Char_Pacing too long will defeat the purpose. The reason for adding an extra one or two stop bits is to prevent the problem where the SERIN software UART can misframe on a repetitive pattern and what it takes for the start bit may well be bit 3, 4, 5, etc. By giving the system 2 or 3 stop bits the SERIN command will fall into sync in just a couple of characters.

HTH
Brian

Good call, never really thought of that. I'm going to add that to a couple of my RF projects and see what happens. As it is, at 9600, I'm losing a few bytes here and there at the longer ranges. Maybe the 'extra stop bit' will help out.

[oneohthree]

I got serin to partially work on the receiver side (with and without wireless). The problem I am having now is it seems like after I decode it I have about 4 extra bits at the end of my decoded sequence. How do I get rid of it?

[skimask]

I got serin to partially work on the receiver side (with and without wireless). The problem I am having now is it seems like after I decode it I have about 4 extra bits at the end of my decoded sequence. How do I get rid of it?

And we're supposed to be able to help you fix that because we can see what your code looks like, right?

[oneohthree]

Here is my revised code:

------------------------------------------------------------------------------------------------------------------
'Transmitter Code
Include "Modedefs.bas"
v var word 'v is a byte to be encoded
counter var byte 'counter is a byte
encoded var word 'encoded is a word sized variable that holds the encoded byte v
'Code to be transmitted
v = %1101 '1101 in Binary
'Manchester Encoding
For counter = 0 to 3 'number of bits to be encoded (4 bits)
If v.0[counter]=0 Then encoded.0[counter*2]=0 'if it is a zero make the first bit 0 encoded.0[counter*2+1]=1 'make the second bit 1
Else
encoded.0[counter*2]=1 'if it is a 1 make the first bit 1
encoded.0[counter*2+1]=0 'make the second bit 0
EndIf
Next counter
'Serial Out
serout PORTB.0, t2400, [$55,$55, $55, $aa, encoded] 'serial out in pin 0 using non-inverted 2400 bps to encoded
--------------------------------------------------------------------------------------------------------------------------------
'Receiver Code
Include "Modedefs.bas"
s var word 's is a byte to be encoded
B0 var byte 'B0 is a byte
B1 var byte 'B1 is a byte
counter var byte
encoded1 var word 'encoded1 word sized variable that holds the encoded byte v
action var byte 'action variable
alert var byte 'alert variable
B0=1 'hardwired address
B1=1 'hardwired address

'Decoding
waitfor55:
serin PORTB.0, t2400, encoded1: if encoded1 = $55 then goto waitfor55
waitforaa:
serin PORTB.0, t2400, encoded1: if encoded1 = $aa then goto waitforaa

serin PORTB.0, t2400, encoded1 'serial in to pin 0, a non-inverting 2400 bps to encoded1
serout PORTB.3, t2400, [encoded1]
loop:
For counter = 0 to 3
s.0[counter]=encoded1.0[counter*2] 'proceed through counter and copy encoded1 to s
Next counter
goto loop
End
serout PORTB.3, t2400, [s] 'serial out to pin 3, a non-inverting 2400 bps, to s

'Tracking code
If (s.2==0) & (s.3==0) Then 'If the code matches 00 then it is in the tracking mode

If (s.0==B0) & (s.1==B1) Then 'If the address matches then
s.2=1 'Change the third bit to 1
action = s.2 'action becomes 1
alert = 0 'alert becomes 0
serout PORTB.1, t2400, [s] 'Send the changed word back, serial out to pin 1, a non-inverting 2400 bps, to s
Else
s.2=0 'Since the addresses does not match do not change anything
action = s.2 'action becomes 0
alert = 0 'alert becomes 0
serout PORTB.1, t2400, [s] 'Send the changed word back, serial out to pin 1, a non-inverting 2400 bps, to s
Endif
Endif

'Tracking and Finding code
If (s.2==0) & (s.3==1) Then 'If the code matches 01 then it is in the tracking and finding mode

If (s.0==B0) & (s.1==B1) Then 'If the address matches then
s.2=1 'Change the third bit to 1
action=s.2 'action becomes 1
alert=1 'alert becomes 1
serout PORTB.1, t2400, [s] 'Send the changed word back, serial out to pin 1, a non-inverting 2400 bps, to s
High 2
Else
s.2=0 'Since the address does not match do not change anything
action=s.2 ;action becomes 0 and alert is also 0
alert=0
serout PORTB.1, t2400, [s] 'Send te changed word back, serial out to pin 1, a non-inverting 2400 bps, to s
Endif
Endif

[skimask]

[QUOTE=oneohthree;35632]Here is my revised code:

That code is entirely TOO complicated for the job you are trying to get done...
Hang tight for a bit...

[skimask]

'Transmitter Code
Include "Modedefs.bas"
v var byte : counter var byte : encoded var byte : v = %1101
main:
For counter = 0 to 3
If v.0[counter]=0 Then
encoded.0[counter*2]=0
Else
encoded.0[counter*2]=1 : encoded.0[counter*2+1]=0
EndIf
Next counter : serout PORTB.0, t2400, [ $55 , $55 , $55 , $aa , encoded ]
goto main



'Receiver Code
Include "Modedefs.bas"
s var byte : B0 var byte : B1 var byte : counter var byte : cnt55 var byte
encoded1 var byte : action var byte : alert var byte : B0=1 : B1=1

main:
cnt55 = 0

waitfor55:
serin PORTB.0, t2400, encoded1

if encoded1 = $55 then
cnt55 = cnt55 + 1 'got $55, inc cnt55 by 1
if cnt55 = 3 then goto waitforaa 'if we got 3 in a row check for $aa
else
goto main 'if not $55, reset counter at main and restart
endif
goto waitfor55

waitforaa:
serin PORTB.0, t2400, encoded1
if encoded1 <> $aa then goto main 'restart, didn't get right leader

serin PORTB.0, t2400, encoded1 : serout PORTB.3, t2400, [encoded1]

For counter=0 to 3:s.0[counter]=encoded1.0[counter*2]:Next counter
serout PORTB.3, t2400, [s]

'Tracking code
If (s.2==0) & (s.3==0) Then
If (s.0==B0) & (s.1==B1) Then
s.2=1:action = s.2:alert = 0:serout PORTB.1, t2400, [s]
Else
s.2=0:action = s.2:alert = 0:serout PORTB.1, t2400, [s]
Endif
Endif

'Tracking and Finding code
If (s.2==0) & (s.3==1) Then
If (s.0==B0) & (s.1==B1) Then 'If the address matches then
s.2=1:action=s.2:alert=1:serout PORTB.1, t2400, [s]:High 2
Else
s.2=0:action=s.2:alert=0:serout PORTB.1, t2400, [s]
Endif
Endif

Your logic for getting the leader bytes and stuff was messed up, so I rewrote it a bit.

But I still think this is entirely too convoluted.
What exactly are you trying to do? Because this seems a bit goofy to me, all this bit manipulation and such. Even though it's a short program, it just seems to me like you'll get yourself stuck in future trying to figure out what you were trying to do in the first place.