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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 1st Oct 2021, 5:54 pm   #521
Slothie
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Default Re: Ortonview PCB

Quote:
Originally Posted by SiriusHardware View Post
I'm wondering if Slothie has been able to make progress with getting the code to run in an 887, the device the code was originally meant to run in. If so we could use the extra pin freed up to provide a blanking control signal spanning the UART initialisation phase only when the screen half being rendered is in normal (not inverse) mode.
In short, yes but no.

I have made progress, in that I have determined that there are a couple of registers needing clearing before the Ortonview will do anything, but now it seems very unstable. It seems to run sometimes then not at others. If you tap the board, especially in the vicinity of the crystal, it works for a short while except the vertical sync seems to be all over the place. This is with the Ortonview not connected to the MK14.
I think there might be more work required to get the configuration fuses working properly, perhaps the oscillator is not starting properly. Its been a long while since I've played seriously with PICs and its taking time to get up to speed with all the intricacies of them.

I do recall that at one point Karen decided to move functions from one port to another, I don't recall why but that also might be an issue.

I have had a week or so off from the project due to other things but I'll get down to testing it again this weekend, I think I need to check the config settings bit by bit.

If anyone wants to look at where I am at the moment its at https://bitbucket.org/IanKRolfe/orto...src/PIC16F887/

(Note: The HEX file in the repository is not the HEX file generated from the latest source, MPLAB squirrels that away somewhere else. I believe the HEX file in the repository is the "vanilla" pic 877 #692 version, so ignore that.
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Old 1st Oct 2021, 7:11 pm   #522
Mark1960
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Default Re: Ortonview PCB

I’ve been thinking about the issue with the 877A in graphics mode and re-reading the original thread. If I understand correctly the first working code did not have the issue, but then after Karen improved the time available to the 8060 the graphics mode showed the issue. I don’t have any 877A or 887 yet, they are still on my shopping list, but if I read the thread correctly the issue is the shifting of the display by one character pixel left and right in alternate frames. I’m thinking this might have been introduced by an optimisation of the timing of sync signals that Karen might have made, considering she was always quite particular to achieving perfection. Anyway I’m wondering if the graphics mode issue is caused by an odd number of cycles between frames causing an issue with sync of the tx clock in graphics mode with the 877A. I’m assuming here that the 877 resets the prescaler on init of the clocked serial and the 877A does not. I would suggest either adding or removing a single instruction cycle from the vertical synch to see what effect that has, it should still be acceptable synch timing for a tv.
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Old 1st Oct 2021, 7:19 pm   #523
Mark1960
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Default Re: Ortonview PCB

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Originally Posted by Slothie View Post
I do recall that at one point Karen decided to move functions from one port to another, I don't recall why but that also might be an issue.
This was when she made the change from using 887 to 877. Was it for ttl compatibility of the 877 inputs on the mk14 data bus?
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Old 1st Oct 2021, 8:41 pm   #524
SiriusHardware
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Default Re: Ortonview PCB

Yes, I think there was a particular 877 port she wanted to use for the databus hence a very late change to the assignment of ports. It coincided with her decision to use the 877 instead of the 887, so, worst case scenario, there may be reason to change it back to the original wiring but still take into account that one of the page select pins also has to operate in a dual mode.

Another possibility is to (reluctantly) change to the PLCC packaged version of the 877 / 877A because that gets you a couple of extra port pins - but they can only realistically be used on a PCB, trying to hand-build without a PCB or at least a pin breakout board would be tedious in the extreme.

I do have some '44 pin PIC Demo' PCBs of the type which originally came with the Pickit 3 - we bought a number of those at work but we only really needed the programmers so the boards were up for grabs so I grabbed them. They typically came with PIC16F877 (QFP) versions fitted although they will accept QFP versions of the PIC16F877A, PIC16F887, PIC18F452 etc - but they are fine pitch devices which have to be soldered, of course.
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Old 1st Oct 2021, 9:15 pm   #525
SiriusHardware
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Default Re: Ortonview PCB

Regarding the apparent sensitivity around the crystal area when using the 887, I'm sure the crystal 'type' in the configuration setup needs to be 'HS' rather than 'XT' and I recall when first messing about with the 887 that I had to disable the Low Voltage Programming option (LVPDIS in the 'C' source I posted earlier) because otherwise signals and states applied to the programming pins may try to put the chip into program mode. Of course disabling Low Voltage Programming is not helpful if you only have a low-voltage programmer rather than a PicKit2/3, ICD2 or ICD3 etc.

Last edited by SiriusHardware; 1st Oct 2021 at 9:22 pm.
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Old 2nd Oct 2021, 10:02 pm   #526
Slothie
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Default Re: Ortonview PCB

Quote:
Originally Posted by SiriusHardware View Post
Regarding the apparent sensitivity around the crystal area when using the 887, I'm sure the crystal 'type' in the configuration setup needs to be 'HS' rather than 'XT' and I recall when first messing about with the 887 that I had to disable the Low Voltage Programming option (LVPDIS in the 'C' source I posted earlier) because otherwise signals and states applied to the programming pins may try to put the chip into program mode. Of course disabling Low Voltage Programming is not helpful if you only have a low-voltage programmer rather than a PicKit2/3, ICD2 or ICD3 etc.
That might have something to do with it, I set the LVP fuse because I had put a programming header on the board, although the reset pin is not being used in Karens design so LVP should still work. I could disable it because I "splashed out" on a cheap PICKIT 3 clone that nonetheless seems to work fine
.
I did set the crystal type to HS (or at least, I set them intending that to happen, its always possible I got it wrong, I used the configuration editor on MPLAB and set the config values in the source to match. I should probably use the defined symbols to build up the config values "properly".
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Old 23rd Oct 2021, 10:11 am   #527
Phil__G
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Default Re: Ortonview PCB

Quote:
Originally Posted by SiriusHardware View Post
Regarding the apparent sensitivity around the crystal area when using the 887, I'm sure the crystal 'type' in the configuration setup needs to be 'HS' rather than 'XT'
thats right, HS for a 16Mhz crystal. I always set the config word in the source rather than specifying it when programming, one less thing for me to forget...
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Old 23rd Oct 2021, 10:28 am   #528
Slothie
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Default Re: Ortonview PCB

Quote:
Originally Posted by Phil__G View Post
Quote:
Originally Posted by SiriusHardware View Post
Regarding the apparent sensitivity around the crystal area when using the 887, I'm sure the crystal 'type' in the configuration setup needs to be 'HS' rather than 'XT'
thats right, HS for a 16Mhz crystal. I always set the config word in the source rather than specifying it when programming, one less thing for me to forget...
Yes, I've been playing with it and managed to get it stable by configuring it thus:
Code:
CFG1	EQU _DEBUG_OFF & _LVP_OFF & _FCMEN_OFF & _IESO_OFF & _BOREN_OFF & _CPD_OFF & _CP_OFF & _MCLRE_ON & _PWRTE_OFF & _WDTE_OFF & _FOSC_HS
CFG2	EQU _BOR40V & _WRT_OFF

	__CONFIG _CONFIG1,	CFG1
	__CONFIG _CONFIG2,	CFG2
And initialise the peripherals:
Code:
	ORG	0
	;+changes for '887
	CLRF	ADCON0		;Not sure these    3 strictly necessary after reset...
	CLRF	CM1CON0
	CLRF	CM2CON0
	CLRF	ANSEL		;Disable analogue ports
	CLRF	ANSELH
	;-changes for '887
	MOVLW	B'00010000'	; NRDS pullup others free
And when not connected to the MK14 this is stable, but does not appear to be accessing the "expansion" memory properly, and touching the data lines does not cause random characters as it does with the 877. I need to hook it up to my logic analyser and see if the various signals are OK, its possible there are other things that need initialising.
When I've checked this out and the signals seem plausible I will try connecting it up to the MK14 again.
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