I have a problem that I could use some input on.
When running my code, using a 48Mhz X-tal and no divide (I think this is maximum speed) on my PIC18F4550, some events take to much time to execute.
I am using two interrupts:
RB0INT
RB2INT
And two timers:
TMR0
TMR3
RB2INT is used to detect a change on a 128ppr optical encoder used for volume control.
- When INT occurs it reads the state of two pins to determine direction
- Then it calls one of two Macros that determines if a variable = X or not
- Then it calls a Macro that prints a number on the display
- Then it calls a Macro that bit bangs out a 32-bit long sequence, one bit at the time (8-bits and a Loop 4 times)
Then it returns to main
RB0INT is used to detect a change on a IR receiver.
- When INT occurs it starts TMR0 and switch edge on RB0INT.
- Then it stops the TMR0 at the next INT and reads the value of TMR0, resets TMR0, switch edge on RB0INT and finaly starts TMR0 again.
- It repeats this for all 32-bits of the IR code, keeping count of which bit it is currently processing.
- At every INT it also checks the value it got from TMR0 against a couple of IF arguments to determine if it was a "0" or "1"
- It then either writes a "1" and shifts the byte or just shifts the byte if it is a "0"
- It goes into a Switch when the received bit counter has reached 8,16,24,32 and I store the corresponding byte and reset the original byte
- When the bit counter is 24 I store byte 3 which is the one I am after. and also perform a LSB to MSB and then go to different macros depending on the value of this byte. for example the same macros asI use with RB2INT for volume up and down.
- After 32Bits I reset everything so it is ready to start again with the next IR code that is coming in.
TMR3 is used to scroll one line on a LCD (In my case VFD) I used TMR3 because it was the slowest one at 22Hz
- On TMR overflow the macro goes through a Switch. It does this 5 times, going through all 5 Switches before printing another 16 characters to the display.
Also I am using the USB Slave component, without the service macro. In the main loop I check-RX and respond accordingly.
So, the problem:
When I power on the PIC with everything connected it says "Volume: -96dB" on line 0. When I start playing a song in Spotify on my computer, it sends a string to the PIC via USB slave.
It is then displayed on line 1 on the LCD and starts scrolling exactly like I want it to. So far so good.
When I turn my optical encoder the number value on the display reacts lightning fast and the text is scrolling on line 1 very nicely still.
But when I press the volume up or down button repeatedly, the scrolling text slows down to a crawl and the remote control feels sluggish and sometimes misses a button press.
I had to disable TMR3 directly after RB0INT is triggered and then re-enable TMR3 again when TMR0 flows over at the end of an IR transmission is complete.
That was the only way I could come up with to ensure that every IR code got received.
So what can I do to have a scrolling text that isn't affected by other events (noticeable by the human eye), ensure the IR codes are received without error and keep the responsiveness of the optical encoder?
I have attached my fcf file and I realize that it might be a bit hard to get with all things going on but I have really tried to explain the code with annotations and comments.
Here is what it looks like when the text is scrolling:
http://youtu.be/_5U173JcX2g
What can I do different to speed things up?
One idea I had was to use a separate PIC that takes care of the IR routine and then sends only the one command Byte to the first PIC. But I have never tried using multiple PIC's and don't know what kind of communication I should use. Maybe CAN? something simple but reliable and with few lines
If you spot something I have done wrong please let me know.
Thanks so much for any and all help.
