Three questions about CASE logic
SteveWoodrough
Posts: 190
The last few days Ive been experimenting with CASE logic, and learned a few lessons.
Three questions:
1) How do I describe a CASE where both Ina[pinA] and Ina[pinB] are high? AND / OR do not seem to work. As I RTFM it looks like I need to add conditions together as variable names to determine the logic table. Is there a way to simply compare or add the input addresses?
2) Completely by accident I got the code below to work. I was playing with the CASE logic and decided to start a cog based on certain input pin being pressed. Using the traditional method to stop a cog would give really bizarre results. Rarely the code would work, mostly it would fail, and sometimes the program running in Cog 0 would be shut down if I stopped a cog with:
I had to use:
Any ideas on why that is the case? (pardon the pun)
What exactly (in English) is this code below saying? Ive read why it should be done, but I have never really understood exactly what is being said.
3)
Here is the meat of the experiment in its successful form:
Thank You! Steve
Three questions:
1) How do I describe a CASE where both Ina[pinA] and Ina[pinB] are high? AND / OR do not seem to work. As I RTFM it looks like I need to add conditions together as variable names to determine the logic table. Is there a way to simply compare or add the input addresses?
2) Completely by accident I got the code below to work. I was playing with the CASE logic and decided to start a cog based on certain input pin being pressed. Using the traditional method to stop a cog would give really bizarre results. Rarely the code would work, mostly it would fail, and sometimes the program running in Cog 0 would be shut down if I stopped a cog with:
PUB StopBlink '
if BlinkCog
cogstop(BlinkCog~ -1) 'Stop previously launched cog
I had to use:
PUB StopBlink '
if BlinkCog
cogstop(BlinkCog) 'Stop previously launched cog
Any ideas on why that is the case? (pardon the pun)
What exactly (in English) is this code below saying? Ive read why it should be done, but I have never really understood exactly what is being said.
3)
if BlinkCog
cogstop(BlinkCog~ -1)
Here is the meat of the experiment in its successful form:
CON
_clkmode = xtal1 + pll16x 'Standard clock mode * crystal frequency = 80 MHz
_xinfreq = 5_000_000
VAR
long BlinkStack[100]
byte BlinkCog
long X
OBJ
PUB Main
LEDCase(10,24)
Pub LEDCase(pinA,pinB)
dira[16..23]~~
repeat
waitcnt(clkfreq/5+cnt) 'I set the scan rate so that it's fast, but not
'faster than the blink rate of the LED
Case Ina[pinA]
1 : Outa[23]~~ 'If the input is HIGH, then the LED is HIGH
0 : Outa[23]~ 'If the input is LOW, then the LED is LOW
Case Ina[pinB]
1 : 'If INA Pin B is HIGH
X:= 0 'Reset X to zero, X is used to determine a single instance of the
'CASE given below.
Outa[16]~~ 'If the input is HIGH, then the LED is HIGH
StopBlink
0 : 'If INA Pin B is LOW
X:=X++ 'Post increment X
if X:=1 'On the first cycle, start a cog
StartBlink(20) 'Blink LED
Outa[16]~ 'Set the output to the LED low.
Pub Blink(pin)
dira[pin]~~
repeat
waitcnt (clkfreq/17 + cnt)
! outa[pin]
PUB StartBlink(pin) 'Starts Cruise Control
StopBlink 'Prevent multiple starts
BlinkCog := cognew(Blink(pin), @BlinkStack) 'Launch method in separate COG
PUB StopBlink '
if BlinkCog
cogstop(BlinkCog)'~ -1) 'Stop previously launched cog
Thank You! Steve
Comments
Case ina[ pina..Pinb ] %11 : dosomethingI haven't tested this.
If the pins are not consecutive, you could construct a variable first
Pinvar := ina[ pina ] << 1
pinvar := ina[ pina ] + ina[ pinb ]
Case pinvar
I am sure there is a better way though with less code, this shows a concept in long form.
Regards,
Steve
Case Ina[pinA] 1 : Outa[23]~~ 'If the input is HIGH, then the LED is HIGH 0 : Outa[23]~ 'If the input is LOW, then the LED is LOWI believe a more elegant approach is just one line:
BTW... I'd also suggest using a named constant in place of '23' -- magic numbers in code like this are not terribly meaningful when it comes to function. Better you do something like this:
Points taken, thank you. My main reason for doing this exercise is to develop a better understanding of the CASE logic structure.
What really puzzles me is the way I had to stop the cogs. I could not use the typical:
PUB StopBlink ' if BlinkCog cogstop(BlinkCog~ -1) 'Stop previously launched cogThe only way the program would work was using the cog stop method below.
PUB StopBlink ' if BlinkCog cogstop(BlinkCog) 'Stop previously launched cogWhy would the traditional cog stopping method not work?
Regards,
Steve
Regards,
Steve