Which chip do i use?

[Darrel Taylor]

... The plan wasnt to use these as DMX lights but how hard would that be?

Very!

Got paid to do it once.
Came up with 1 18F as the front end receiving the DMX.
And any number of slaves (8 per PIC).
Up to 512 channels total. (lots of slaves, kinky)

Unfortunately, it was for LED's (high powered one's, but still LED's)
It'll be harder for A/C dimmers.

.

[The Master]

DMX is out then! I dont want this to be any harder than it already is.

Ive just been reading some of Matt's threads. I can see a few references to the boxes he made for me. Just to add, those boxes are still working perfect after something like 3 or 4 years. Nice job!

Anyways. I cant seem to find much in those threads about the bits im stuck on. There is 1 thing that can be learned from them tho. Dont rivet triacs to anything! I had to replace one once without getting to the solder side of the PCB.

This thread or more specificly the last post is quite interesting. Can someone tell me if the following is correct.
There is a receive flag. Possibly whatever PBP uses as a boolean value. When serial data arrives at the chip this flag is set to true.

RCREG returns the first byte from the serial buffer and removes it from the buffer. If this causes the buffer to be empty (that was the last byte) then the RX flag is set to false.

I take it this uses the hardware UART thing to add data to a buffer (with no code)

[The Master]

Ive just found another thread with sample code of using UART and interrupts. It looks simple enough so im gonna test it out when i get back home (stupid work, ruining my day :P)

[The Master]

Ive had a go at writing some code. This is just for the serial part. The idea is that if the chip gets chr(255) then it sets the next 16 bytes to the brightness levels (Later to be used to control the triacs).

datapos var byte
newbyte var byte
brightness var byte [15]

trisc=%11111111
spbrg=129
rcsta=%10010000

datapos=16

loop:
if pir1.5=1 then
    newbyte=rcreg
    if newbyte=255 then
        datapos=0
    else
        if datapos!=16 then
            brightness(datapos)=newbyte
            datapos=datapos+1
        endif
    endif
endif
goto loop

I do have a few questions about it though. Can this only be used on a pin labeled RX? For this chip the pin labeled RX is RC7.

An example i have says "RCSTA = %10010000 ' Enable serial port and continuous receive". What are we setting here? Are we telling it which pin is being used or is it just a standard value that means "on"?

Is my code any good or should i scrap it and start again? :P

[The Master]

Ive just tried out Darrel's code again now im on this new chip and it compiled first time without me having to edit anything I used it to monitor the falling edge and i connected 2 diodes up. I did a quick test...

ToggleLED1:
pause 5
high PORTd.7
pause 1
low PORTd.7

And the bulb lights up at half brightness WOO! Im just having a read through "Multiple Software PWM". Then ill have to figure out how to add serial to it but it looks like i can use his code for that too

[The Master]

Ive written some test code using DT's example

INCLUDE "DT_INTS-14.bas"     ; Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ; Include if using PBP interrupts

resolution var byte
x var byte

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler    INT_INT,  _ToggleLED1,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@   INT_ENABLE   INT_INT     ; enable external (INT) interrupts

Main:
    for resolution=0 to 100
        pause 1
    next
    for resolution=100 to 0 step -1
        pause 1
    next
GOTO Main

'---[INT - interrupt handler]---------------------------------------------------
ToggleLED1:
    for x=100 to 1 step -1
        if resolution=x then
            high portd.7
        endif
        pauseus 150
    next
    low portd.7
@ INT_RETURN

It works perfectly except the bulb fades out half way then pauses slightly then fades out completely. It also fades as its coming back in. Does anyone know why that is and how to fix it?

[The Master]

I think ive been looking at this the wrong way round. Ive had the multimeter on one of the boxes Matt made (8 triacs are riveted to the side so i cant see under the PCB). From what i can see the interrupt pin isnt connected at all. I think he has a main loop which just waits for a certain pin to go low (for the zero-crossing) then executes the bit to control how bright everything is. As for the serial input i think that is where the interrupt comes in. Either that or there is no interrupt at all and he checks that in the main loop too. Now its starting to sound simple

For now im gonna use the same chips Matt used and see if i can make his circuit work on a breadboard. Then i can copy the hex code to the new chips. That gives me 8 outputs so ill need 2 chips per circuit but they are cheaper than 1 big one.

1 thing i find weird about his circuit is that MCLR doesnt appear to be connected to anything :S