keithWelp, this is finals week, so don’t expect anything new to show up until after April 28th, 2005.
But, this doesn’t mean I’ve forgotten about this project! I am very much interested in moving this forward.
I’m not really sure what my next step is, but I have to start approaching this using the “scientific method”, and start to isolate my issues. So far, the testing and everything is haphazard, and I find myself testing stuff that I’ve done before because I’ve partially forgot what the results of earlier tests were. This is bad, wastes time, etc.
Part of my problems is that the signal has multiple lengths, sometimes it’s a perfect 4us, 6us, or 8us grouping, and sometimes it’s 5.56us or 7.63us. You get the picture. The code has to be able to handle these different situations the same. Also, I think I’m in my ISR simply way too long. I’m missing edges, and this is where I’m screwing up.
If anyone is interested, I’ve included my SX/B code below. You can also find it here for downloading.
IRC_CAL IRC_SLOW
FREQ 50000000
' -------------------------------------------------------------------------
' Variables
' -------------------------------------------------------------------------
inputpin var RB.0 'data from drive
outputbyte var RC 'data to pc
byteready var RB.2 'notify pc byte is ready
pcack var RB.3 'pc saying it got the byte
storevalue var bit 'bit to store in the shift reg
samplepin var bit 'actual value of pin at interrupt
numstoredbits var byte '# of stored bits in shift reg
storedata var byte 'actual stored data
seenedge var bit 'seen an edge or are we idly?
pending var byte 'swapped with wkpnd_b, RTCC or edge?
validhigh var byte 'how many high bits have we seen in a row
inputready var bit 'used for isr to tell main value is ready
'to be stored
currpos var byte 'current STORE position in FIFO
xferpos var byte 'current XFER position in FIFO
myarray var byte(16) 'FIFO storage
' -------------------------------------------------------------------------
INTERRUPT
' -------------------------------------------------------------------------
ISR_Start:
'RTCC = 0
RB.1 = 1 'for debugging
samplepin = inputpin 'grab the pin
pending = 0
wkpnd_b = pending 'is this an edge or a rollover
if pending.0 = 1 then processedge
if seenedge = 0 then goback 'are we idle?
if samplepin = 0 then goback 'we shouldn't be at an edge here
inc validhigh
if validhigh > 3 then goidle 'more than 3 highs? go idle
storevalue = 0
inputready = 1 'tell main the value is ready to be stored
goto goback
goidle:
seenedge = 0 'erase the edge we saw before
validhigh = 0 'reset and start over
goto goback
processedge:
seenedge = 1 'we've now seen an edge!
validhigh = 0 'this should already be zero
storevalue = 1 'store a 1 for an edge
inputready = 1 'tell main its ready
RTCC=0
goback:
wkpnd_b = 0
RB.1 = 0 'for debugging
returnint 88
PROGRAM start_point
' Program Code
' -------------------------------------------------------------------------
start_point:
'setup port b
TRIS_B=%11111001 'direction bits rb.0 input, rb.1 & rb.2 output
ST_B = %11111110 'schmitt trigger for our drive input
WKPND_B = 0 'clear pending interrupts
WKED_B = %11111111 'set falling edge trigger
WKEN_B = %11111110 'enable drive input interrupts
PLP_B = %11111110 'enable pullups
'setup port c
TRIS_C=0 'enable port c for output
PLP_C = %00000000
numstoredbits = 0
byteready = 0
seenedge = 0
pending = 0
validhigh = 0
inputready = 0
currpos = 15
xferpos = 15
' turn on interrupts
OPTION = $88
repeat:
if byteready = 1 then skipthis 'we are already xferring something
if currpos = xferpos then skipcheck 'we have nothing to send and everything has been ack'd
outputbyte = myarray(xferpos)
byteready = 1 'put the byte on the port and tell PC
goto skipcheck 'we don't need to check an ack this soon after we raised it
skipthis:
if pcack = 0 then skipcheck
byteready = 0
if xferpos > 0 then skipassign
xferpos = 16
skipassign:
dec xferpos
skipcheck:
if inputready = 0 then repeat
inputready = 0
if numstoredbits > 0 then notzerobits
storedata = storevalue
numstoredbits = 1
goto repeat
notzerobits:
storedata = storedata < < 1 ' shift left to make room for next bit
if storevalue = 1 then storeaone
storedata = storedata | 0 ' store a zero
goto nextstep
storeaone:
storedata = storedata | 1 'store a one
nextstep:
inc numstoredbits
if numstoredbits < 8 then repeat
'else output data to FIFO, eventually to the PC
myarray(currpos) = storedata
if currpos > 0 then skipcurrreset
currpos = 16
skipcurrreset:
dec currpos
numstoredbits = 0
storedata = 0
goto repeat
Stick with me and feel free to comment. I need the help!
Add comment