Capture without CCP

[boroko]

Is it possible to capture the TMR1 counts without a CCP and still let the counter continue?

The problem: Trying to use a 18 pin chip for space, currently a 18F1330.

I need the Power Control PWM as I need at least 2 different PWMs, three would be better.

The TMR1 is using a prescaler of 1:1 and a preload of 5543 (@8mHz) for a cycle of about 30 mS.

That cycle sends a ultrasonic transmit pulse and starts looking for a return echo.
INT2_INT (eventually CMP2_INT) is used to catch the echo and grab the count from TMR1. I spent the last 6 hours learning that when you load TMR1, you need to load TMR1H first, before TMR1L. I won't tell you how many times I read the datasheet before I realized that one. I have the cycle stable now, but the capture of the elapsed time is still wonked. I can't see where.

I could go to a 18F2331 and get CCP and PCPWM, but that puts me at 28 pin and I really don't have the room.

If anyone sees something that here, I sure would appreciate the advice.
'************************************************* *****************
'* Name : CS-Sonic1330_2f.BAS *
'* Author : Mark A.Rokus *
'* Notice : Copyright (c) 2009 Controlled Surroundings Inc. *
'* : All Rights Reserved *
'* Date : 3/25/2009 *
'* Version : 1.0 *
'* Notes : 18F1330 @ 8mHz, PBP 2.50b, MCS 3.0.0.0
'* Pulse out on PORTB.0 every ~30 mS (TMR1: _Transmit)
'* external circuit echos back pulse on PORTB.2 (INT2)
'* between 3mS and 23mS. After transmit, enable INT2_INT and
'* get count to "EchoTime". Send # out on HSER to debug.
'* This is the core of the code that is failing. Increasing the
'* result count with every echo while the return pulse is steady????
'************************************************* ***************
DEFINE OSC 8
DEFINE HSER_RCSTA 90h
DEFINE HSER_TXSTA 24h
DEFINE HSER_BAUD 9600
DEFINE HSER_CLOERR 1 ' automatic clear overrun error
clear

TRISB = %01000100 ' PWM1,3,5 outputs,RB2=INT, RB0,2,3: DIO
ADCON1 = %00001111 ' Set up ADCON1 no matter what you're doing!!!!!!
T0CON = %10001000 ' On, 16 bit, Prescaler Bypassed (1:1)
T1CON = %10000001 ' 16bit, 1:1 ps, 30 mS INT
CMCON = %00000100 ' CMEN2 to enable the comparator
CVRCON = %10100010 ' REF on, REF voltage @ 1.563
RCON = %00011111 ' NO Priority for interrupts
OSCCON = %11111110 ' INTOSC, 8MHz,

hserout [" 1330-2g",13,10]
'::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::
INCLUDE "DT_INTS-18.bas" ' Base Interrupt System
INCLUDE "ReEnterPBP-18.bas" ' Include if using PBP interrupts
'::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::
' Variable definition
'::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::::::::::::::::
EchoTime Var word
PL1lo con $A7 ' Preload for TMR1 LO byte, Cycle time
PL1hi con $15 ' Preload TMR1 HI byte ,PL =5543/ 1:1

ASM
INT_LIST macro ; IntSource, Label, Type, ResetFlag?
INT_Handler INT2_INT, _GetEcho, PBP, yes ;straight I/P
INT_Handler TMR1_INT, _Transmit, PBP, yes
endm
INT_CREATE ; Creates the interrupt processor
ENDASM
'@ INT_ENABLE INT2_INT
@ INT_ENABLE TMR1_INT ; enable Timer 1 interrupts
'************************************************* **************************
Start:

Mainloop:

hserout [#EchoTime,13,10]
pause 500

goto Mainloop
'*********** Int handlers **************************************************

'---[INT - interrupt handler]-----------------------------------------------
' TMR1 cnt up from start of TX. INT when RX, get counts into EchoTime
GetEcho:
T1CON.0=0 ' Stop TMR1
echoTime.Highbyte=TMR1H ' capture the counts
echoTime.Lowbyte=TMR1L
' echoTime.Highbyte=TMR1H ' capture the counts
T1CON.0=1 ' Restart the TMR1 to finish cycle
@ INT_RETURN

'---[TMR1 - interrupt handler]-------------------------------
' TMR1 = 16 bit, 1:1, 65535 - 5543(preload) ~30 mS cycle
Transmit:
@ INT_DISABLE INT2_INT ; Disable external ints to stop Echo RX
'T1CON = %10000001 ' 16bit, 1:1 ps, 30 mS INT
TMR1H = PL1hi 'Preload HI byte
TMR1L = PL1lo 'Preload LO byte =

asm
BSF PORTB,0
NOP ; need 7 NOPs between changes for 125kHz @ 8mHZ
NOP
NOP
NOP
NOP
NOP
NOP
BCF PORTB,0
NOP
NOP
NOP
NOP
NOP
NOP
NOP
endasm

@ INT_ENABLE INT2_INT
@ INT_RETURN

end

Thanks
Bo

[Acetronics2]

Hi, Boroko

I think in the Microchip datas ( Midrange manual ), there's a chapter on how to use timers as "free running timers"

Example 12-2: Reading a 16-bit Free-Running Timer

Example 12-3: Writing a 16-bit Free Running Timer


Ok ... ASM, but is it really a problem ??? certainly not with Darrel's I.I.

Alain

[Darrel Taylor]

I spent the last 6 hours learning that when you load TMR1, you need to load TMR1H first, before TMR1L.
Yes, with RD16 set, you load the highbyte first, then when you load the lowbyte, both bytes a written to the timer at the same time.

But when reading a timer with RD16, you have to read the lowbyte first. That puts the highbyte in a buffer that can be read in the next instruction.

If you read the highbyte first, you get the value that was left in the buffer the last time you read/wrote the timer, then the lowbyte of the current timer value.

Also, when using RD16, you don't need to stop the timer when reading or writing to the timer.

For something like this where you need Critical timing ... the interrupt handlers should be ASM. Saving/Restoring PBP's system variables to get in/out of a PBP interrupt will throw the results off considerably.

None of the statements in your handlers use any PBP system variables. So you can just change the handers "type" to ASM without actually having to write it in ASM.

hth,

[boroko]

Thanks guys,

Alain, I had not thought to look at the mid-range ref manual. Seeing how they handled it helped to see it better. The longer I'm at the less I'm scared by the asm. I may not be able to write it very well, but it is getting easier to see how it works. I'm not religious about a particular method. I'm interested in results and PBP has given me the best chance to get powerful ones with the least amount of pain.

Darrel, thanks for going over these details. I was having a blind spot pulling them out of the data sheet.

It may seem like a small thing to you guys, but your assistance has helped me (and I'm sure others) get through things that in the past, would have pushed me to give up on out of pure frustration.

Bo

Wohoo! Stable numbers echoing back! Thank you so much.....

[boroko]

None of the statements in your handlers use any PBP system variables. So you can just change the handers "type" to ASM without actually having to write it in ASM.

I guess that means I don't need to include ReEnterPBP-18.bas either. Do I understand that correctly?

Bo

[Darrel Taylor]

Correct!

Including the file will use some additional RAM and program space that isn't needed.

But it won't adversely affect the program if it's there.
<br>