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Discussing the Open Source FPGA Amiga Project
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 Post subject: PIC18F26K20
PostPosted: Wed Apr 18, 2012 4:47 pm 
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Joined: Wed Jan 06, 2010 7:47 pm
Posts: 25
Hi all,

if anyone is interested, I am in the process of putting a PIC18F46K20 on my Minimig. It is pin-compatible with the 252 but has a lot more code space and RAM. To use it, I ported the PIC firmware to MCC18 and it compiles with the free lite version and fits on the chip without any optimisation enabled but I have not tested it yet (as my chips are due to arrive tomorrow morning). The chip can run at 64MHz with its internal oscillator and PLL, so it should be possible to apply the Fast SPI hack and run the SD card at 16MHz (the peripheral runs at a max of Fosc/4, so 24MHz is not possible).

If all goes well, it should also be possible to back port some of the other nice features of the ARM controller without spending anything (the chip costs £2.50).


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 Post subject: Re: PIC18F26K20
PostPosted: Thu Apr 19, 2012 10:31 am 
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Joined: Mon Dec 01, 2008 6:41 pm
Posts: 166
@Zardoz
This sounds like a very cost effective way of speeding up IO access and allowing additional features to be made available without requiring the ARM addon board on the standard v1.1 Minimig.

Am I right in thinking that if the PIC new faster PIC was supplied preprogrammed by and Amiga dealer it would just be a case of swapping out the old slower PIC and fitting the new one with any soldering being required?

Would it also be upgradable with a serial cable like the existing PIC with out the need for and soldering or removing the PIC reflashing it an external writer?

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2MB Minimig with PIC
4MB Minimig with ARM Addon board


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 Post subject: Re: PIC18F26K20
PostPosted: Thu Apr 19, 2012 11:46 am 
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Joined: Wed Jan 06, 2010 7:47 pm
Posts: 25
@dwyloc

It should be a straight drop-in replacement, all the Minimigs I've seen have the PIC seated in a socket. The same bootloader we use on the 18F252 should work on the 18F46K20, so users should still be able to upgrade over serial. For the faster SPI transfers, you will still need to do the little solder bridge mod that you do with the ARM controller.


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 Post subject: Re: PIC18F26K20
PostPosted: Thu Apr 19, 2012 2:24 pm 
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Joined: Mon Dec 01, 2008 6:41 pm
Posts: 166
Zardoz wrote:
@dwyloc
It should be a straight drop-in replacement, all the Minimigs I've seen have the PIC seated in a socket. The same bootloader we use on the 18F252 should work on the 18F46K20, so users should still be able to upgrade over serial. For the faster SPI transfers, you will still need to do the little solder bridge mod that you do with the ARM controller.

Sounds good, as I would need want to get my Minimig that is still using its PIC upgraded to 4MB anyway I am sure Amigakit could do the SPI mod at the same time for me and yes the PIC chip on both my Minimigs is/was socketed (one was upgraded to have the ARM addon board).

I will look forward to hearing about your progress with the new PIC chip and upgrading my first 2MB Minimig then your new PIC firmware is ready for end user.

Swapping out the PIC chips is no harder than doing a traditional kickstart upgrade on a classic Amiga so I am sure most users should be up to the job if they take things slowly and carefully, I found upgrading to the ARM addon easier than fitting many classic Amiga hardware addons :-)

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2MB Minimig with PIC
4MB Minimig with ARM Addon board


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 Post subject: Re: PIC18F26K20
PostPosted: Thu Apr 26, 2012 4:14 pm 
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Joined: Wed Jan 06, 2010 7:47 pm
Posts: 25
Hey hop,

I thought it's time for a bit of a progress report. I haven't had the time to do much on this apart from the initial port, the basic firmware already works on the PIC18F26K20 but it still has to be compiled with Hitech C. My MCC18 port is breaking the filesystem. Ideally, I'd want it to work properly with MCC18 but Hitech C will do for now. It programs the FPGA ***fast*** but I have some SD timing issues, so the kickstart image gets corrupted and the Amiga crashes on boot.

I'll let you guys know how it goes when I get a bit more time to poke around.


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 Post subject: Re: PIC18F26K20
PostPosted: Wed May 16, 2012 6:06 pm 
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Joined: Wed Apr 11, 2012 8:16 am
Posts: 15
Sounds very interisting to me as i am also to closefisted to spend so much money for the arm board.
I am curious if it will work.


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 Post subject: Re: PIC18F26K20
PostPosted: Fri May 18, 2012 12:44 pm 
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Joined: Fri Apr 24, 2009 10:20 am
Posts: 5
@Zardoz

I hope you can work on it soon. It would be nice to see faster Minimigs. 8-)


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 Post subject: Re: PIC18F26K20
PostPosted: Fri Aug 23, 2013 8:52 am 
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Joined: Mon Dec 07, 2009 3:53 pm
Posts: 26
Hi,
Is there any further progress on this pic replacement ?
Can the SD card read error be due to the SLEW RATE of the Pic18F26K20 ?
Pls try setting the SLRCON to 0x00.
Very interested to use 64Mhz internal Osc and 16Mhz SPI on the unexpanded minimig.


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 Post subject: Re: PIC18F26K20
PostPosted: Thu Aug 29, 2013 12:03 pm 
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Joined: Mon Dec 01, 2008 6:41 pm
Posts: 166
Sadly it would seem this PIC update plan as stalled/failed as Zardoz has not logged in here since August 2012 going by his profile :-(

As it would be nice to have an updated PIC port that fixes the CIA timing errors that cause the odd problem with PIC firmware that are not seen with the ARM addon boards.

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2MB Minimig with PIC
4MB Minimig with ARM Addon board


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