Very useful program!.... But often we have to produce several channels of pulsed signals with some relative delay. Is this option implemented in the program ? How could we use it?

Sorry, this program will only produce PWM with all channels having the same phase. I'm sure it can be done, but just not with this program.

I am using Multi_SPWM on a 16F628 running at 20MHz at a PWM freq of 50Hz, and it it works perfectly as expected - great!. But I also need the PIC to process some serial data at 115200bps (eventually I intend have the processor set 8 channels of PWM output based on serial data sent to the device), so I am playing around with the following code segment, to teach myself how to use the USART and have the code respond to recieved serial data:

------------------------------------------------

' Simple program to handle USART interrupt using PIC16F628A @20MHZ
' ===============================================================
'
' This program allows the user to activate or deactivate
' a LED connected on PORTB.1 pin by sending command from a PC
' terminal software using 9600,n,8,1 setting
'
' User command:
' =============
' 1. If character "1" is received => enable the LED
' 2. if character "2" is received => disable the LED
'
@ DEVICE PIC16F628a, HS_OSC
' System Clock Options
@ DEVICE pic16F628a, WDT_ON
' Watchdog Timer
@ DEVICE pic16F628a, PWRT_ON
' Power-On Timer
@ DEVICE pic16F628a, MCLR_ON
' Master Clear Options
@ DEVICE pic16F628a, BOD_ON
' Brown-Out Detect
@ DEVICE pic16F628a, LVP_OFF
' Low-Voltage Programming
@ DEVICE pic16F628a, CPD_OFF
' Data Memory Code Protect
' Set to CPD_OFF for Development Copy
' Set to CPD_ON for Release Copy
@ DEVICE pic16F628a, PROTECT_OFF
' Program Code Protection
' Set to PROTECT_OFF for Development Copy
' Set to PROTECT_ON for Release Copy

DEFINE OSC 20 ' running at 20 MHZ
CMCON=7
TRISB=%00000010 ' PortB.1 => USART RX pin set to input
' all other pin set to output

' USART setting
' =============
' Since we will not use HSERIN/HSEROUT, we must
' write directly to internal PIC register
TXSTA=$24 ' enable transmit and SPBRGH=1
RCSTA=$90 ' Enable USART and continuous receive
SPBRG=10 ' BAUD RATE = 115200 BAUD

' Interrupt definition
' ====================
PIE1.5 =1 ' enable USART receive interrupt
INTCON.6 =1 ' enable peripheral interrupt

' Alias definition
' ================
RCIF var PIR1.5 ' receiver interrupt
UserLED var PORTB.4 ' the LED that user want to control

' Variable definition
' ===================
DataIn var byte ' use to store RCREG content
Discard var byte ' use to erase RCREG register

' Hardware/software initialisation
' ================================
PORTB=0 ' clear PORTB
on interrupt goto USARTInterrupt

Start:
'main program loop
goto start


disable interrupt
USARTInterrupt:
' Here's the interrupt routine to control the status of the user LED
'
RCSTA=0 ' Disable serial port AND
' clear possible error (FERR,OERR)
datain=RCREG ' Get data
while RCif ' wait untill the RCREG is empty
discard=RCREG ' by reading it and store result in a
wend ' don't care variable

select case datain ' What to do with that data???
case "1" ' User selection = 1
userled=1 ' => Enable the LED
case "2" ' User selection =2
userled=0 ' => disable the LED
end select
RCSTA=$90 ' Re-enable the serial PORT AND
resume ' get out of here
enable interrupt


------------------------------------------------

Now, this code also behaves perfectly - the led responds whenever the correct serial data is recevied. My problem is that I cannot seem to combine this code with Multi_SPWM. I assume this is to be because of some sort of interrupt conflict between the two code segments. Can anyone please help of point me in the right direction?

Kind regards,
Ralph Parkhurst,
Melbourne,Australia.
radio_ralph@norwood.org.au

Hi Ralph,

The Multi-SPWM programs interrupts are done in Assembly Language.

There's no way to combine Basic Language (A.K.A. ON INTERRUPT GOTO) type interrupts, with ASM interrupts.

You could write the USART routines in ASM and be able to add them in to the INT_CODE section.

But then, that assumes you are familiar Assembly Language.

Sorry, I'm not much help.
Darrel Taylor

Hello Darrel, this program you have wriiten works great except, I have been working with it for 2 days now and I can not figure out how to change the DutyCycle within the progam as to change the position of the servos. I wanted to do this by way of a serin command but I have had no luck in doing this. Can you help?

Thanks
Twisted