Raspberry Pi Mini to 1200 Clockport Advice - Page 2

bwldrbst · 28 July 2018, 02:12

I've been working on a similar idea but focused more on the software side. There's some discussion and links to github repos here.

The software allows for multiple streams of data with asynchronous reads and writes over the connection to the Raspberry Pi.

I have a feeling it won't perform well enough for a display but you never know... I'm mainly concerned with input devices, storage and networking.

For now I'm just using the serial port (because it's easy) but it's written in a modular way to support any sort of physical connection people can come up with.

Cheers,

Andrew

betajaen · 28 July 2018, 06:15

Great minds think alike!

Thanks for the link, I shall read over your posts and have a peek at your code.

I'm just going to aim for graphics for now, other stuff like USB/Wifi/storage/co-processor much later (if possible).

zerohp · 28 July 2018, 16:04

Have you considered timing at all? I'm not convinced the GPIO on a Raspberry Pi can be made fast enough to use the clockport. It's not a matter of performance, but whether it works at all.

nogginthenog · 28 July 2018, 19:56

I saw on Stedy's page that the clockport only has 32 x 8-bit addresses.
http://www.ianstedman.co.uk/Amiga/am...lock_port.html

The PI runs a multitasking operating system which not work.

An Arduino (or other microcontroller) would be better. You could wire the 2 chip select pins on the clock port to 2 interrupt pins on the Arduino. and read/write the data bus.

Stedy · 29 July 2018, 00:37

Hi,

I've attached an old design showing a simple circuit to interface to the Clockport. Connecting a Rasberry Pi to the clockport, even with level shifters will not work.

When interfacing to the MC68020 bus, you must de-assert within 1 clock cycle on a read. Translating that to the Raspberry Pi GPIO, when the Amiga CPU reads from the Raspberry Pi, the GPIO port is set as an output and drive the data bus. If you do not stop driving within 70ns of RTC_CS or SPARE_CS going high, you risk corrupting the next RAM access, that access my have your next instructions/code and will be corrupted by your Raspberry PI. Can you change the 8 data pins from output to input in 70ns?

The Clockport is not fast. A single byte access takes 1us. So the maximum, theoretical data rate is 1/1us or 1MHz which equates to 1 Mbyte/sec. You'll never achieve this due to the Amiga doing other things. Allow 50% at best, this give a bandwidth of 500 KByte/sec. Nowhere near enough for graphics as 320x256 x 16 colours @ 50Hz would need 8 Mbyte/sec.

If you add the correct logic, you can connect the Raspberry Pi to the Amiga.

betajaen · 29 July 2018, 06:54

Hi Stedy,

Thank you for your input, but it looks less and less promising then.

I wouldn't be using the Linux operating system though. Just a simple copy-paste assembly bootloader, which runs a C based program that acts as the driver interface, does the graphics, etc. No Operating System required.

But from the very beginning, I've wondered if it's possible, then if it is practical.

rare_j · 29 July 2018, 10:24

Is doing something with the trapdoor slot viable?

idrougge · 29 July 2018, 12:08

Not in any practical way since it is usually filled up with an accelerator already. Unless you want to go the full tower route, and why would you do that for a budget solution?

rare_j · 29 July 2018, 13:57

Well that's true but if there was some way to utilise the 1/2 gb of ram, or wifi connection, or sd card storage it would be fun for those with a stock machine.
Stedy has given a detailed view on the challenges of using the clockport, which made for interesting reading.
I wonder if anyone has any similar insight into using the cpu slot as an interface.

betajaen · 29 July 2018, 16:04

I think using the accelerator slot isn't really a solution.

I chose the clock port, because I was hoping anyone could just buy a cable, and a raspberry pi anyway. Download an image to put on a SD card, and it would just go. No production of PCBs, no soldering, etc.

I wonder though if the Cybergraphics/Picasso libraries are more efficient than just sending the contents of the graphics buffer. It must have vector drawing functions, and uploading bitmaps/sprites, then placing them on the screen as needed. The 'card'/driver program for the Amiga 2000 indicates this - just sending commands.

idrougge · 29 July 2018, 19:13

The very fact that you need an exotic A1200 CPU connector makes the Raspberry connection once more into a false start since you're throwing a lot of money towards using something which was meant to be a budget solution.

The CGX/P96 API does of course support high-level operations, but you're still using the card over the slowest bus known to the Amiga.

betajaen · 29 July 2018, 19:54

Oh well. Sadly, this doesn't seem possible.

It was worth a chat about. Thank you to everyone for your help, and insight.

kolla · 30 July 2018, 15:26

Hey, there are other uses for a pi there, like fast serial interface to the Linux on the pi...
* bridge to ethernet
* bridge to wifi
* bridge to USB

Look here:
http://eab.abime.net/showthread.php?t=92931

EDIT: boy, did I mess up URL-editing

nidge · 06 August 2018, 11:38

Interseting discussion, a pity the Pi idea could not be done

29 July 2018, 00:37	#25
Stedy Registered User Join Date: Jan 2008 Location: United Kingdom Age: 46 Posts: 733	Hi, I've attached an old design showing a simple circuit to interface to the Clockport. Connecting a Rasberry Pi to the clockport, even with level shifters will not work. When interfacing to the MC68020 bus, you must de-assert within 1 clock cycle on a read. Translating that to the Raspberry Pi GPIO, when the Amiga CPU reads from the Raspberry Pi, the GPIO port is set as an output and drive the data bus. If you do not stop driving within 70ns of RTC_CS or SPARE_CS going high, you risk corrupting the next RAM access, that access my have your next instructions/code and will be corrupted by your Raspberry PI. Can you change the 8 data pins from output to input in 70ns? The Clockport is not fast. A single byte access takes 1us. So the maximum, theoretical data rate is 1/1us or 1MHz which equates to 1 Mbyte/sec. You'll never achieve this due to the Amiga doing other things. Allow 50% at best, this give a bandwidth of 500 KByte/sec. Nowhere near enough for graphics as 320x256 x 16 colours @ 50Hz would need 8 Mbyte/sec. If you add the correct logic, you can connect the Raspberry Pi to the Amiga. Attached Thumbnails

30 July 2018, 15:26	#33
kolla Banned Join Date: Nov 2007 Location: Trondheim, Norway Posts: 1,893	Hey, there are other uses for a pi there, like fast serial interface to the Linux on the pi... * bridge to ethernet * bridge to wifi * bridge to USB Look here: http://eab.abime.net/showthread.php?t=92931 EDIT: boy, did I mess up URL-editing Last edited by kolla; 30 July 2018 at 15:33.

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28 July 2018, 02:12	#21
bwldrbst Registered User Join Date: Nov 2015 Location: Perth, Australia Posts: 73	I've been working on a similar idea but focused more on the software side. There's some discussion and links to github repos here. The software allows for multiple streams of data with asynchronous reads and writes over the connection to the Raspberry Pi. I have a feeling it won't perform well enough for a display but you never know... I'm mainly concerned with input devices, storage and networking. For now I'm just using the serial port (because it's easy) but it's written in a modular way to support any sort of physical connection people can come up with. Cheers, Andrew

28 July 2018, 06:15	#22
betajaen Registered User Join Date: Apr 2018 Location: Wales, UK Age: 41 Posts: 102	Great minds think alike! Thanks for the link, I shall read over your posts and have a peek at your code. I'm just going to aim for graphics for now, other stuff like USB/Wifi/storage/co-processor much later (if possible).

28 July 2018, 16:04	#23
zerohp Registered User Join Date: Dec 2017 Location: Champaign, IL / USA Posts: 7	Have you considered timing at all? I'm not convinced the GPIO on a Raspberry Pi can be made fast enough to use the clockport. It's not a matter of performance, but whether it works at all.

28 July 2018, 19:56	#24
nogginthenog Amigan Join Date: Feb 2012 Location: London Posts: 1,309	I saw on Stedy's page that the clockport only has 32 x 8-bit addresses. http://www.ianstedman.co.uk/Amiga/am...lock_port.html The PI runs a multitasking operating system which not work. An Arduino (or other microcontroller) would be better. You could wire the 2 chip select pins on the clock port to 2 interrupt pins on the Arduino. and read/write the data bus.

29 July 2018, 06:54	#26
betajaen Registered User Join Date: Apr 2018 Location: Wales, UK Age: 41 Posts: 102	Hi Stedy, Thank you for your input, but it looks less and less promising then. I wouldn't be using the Linux operating system though. Just a simple copy-paste assembly bootloader, which runs a C based program that acts as the driver interface, does the graphics, etc. No Operating System required. But from the very beginning, I've wondered if it's possible, then if it is practical.

29 July 2018, 10:24	#27
rare_j Zone Friend Join Date: Apr 2005 Location: London Posts: 1,176	Is doing something with the trapdoor slot viable?

29 July 2018, 12:08	#28
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,332	Not in any practical way since it is usually filled up with an accelerator already. Unless you want to go the full tower route, and why would you do that for a budget solution?

29 July 2018, 13:57	#29
rare_j Zone Friend Join Date: Apr 2005 Location: London Posts: 1,176	Well that's true but if there was some way to utilise the 1/2 gb of ram, or wifi connection, or sd card storage it would be fun for those with a stock machine. Stedy has given a detailed view on the challenges of using the clockport, which made for interesting reading. I wonder if anyone has any similar insight into using the cpu slot as an interface.

29 July 2018, 16:04	#30
betajaen Registered User Join Date: Apr 2018 Location: Wales, UK Age: 41 Posts: 102	I think using the accelerator slot isn't really a solution. I chose the clock port, because I was hoping anyone could just buy a cable, and a raspberry pi anyway. Download an image to put on a SD card, and it would just go. No production of PCBs, no soldering, etc. I wonder though if the Cybergraphics/Picasso libraries are more efficient than just sending the contents of the graphics buffer. It must have vector drawing functions, and uploading bitmaps/sprites, then placing them on the screen as needed. The 'card'/driver program for the Amiga 2000 indicates this - just sending commands.

29 July 2018, 19:13	#31
idrougge Registered User Join Date: Sep 2007 Location: Stockholm Posts: 4,332	The very fact that you need an exotic A1200 CPU connector makes the Raspberry connection once more into a false start since you're throwing a lot of money towards using something which was meant to be a budget solution. The CGX/P96 API does of course support high-level operations, but you're still using the card over the slowest bus known to the Amiga.

29 July 2018, 19:54	#32
betajaen Registered User Join Date: Apr 2018 Location: Wales, UK Age: 41 Posts: 102	Oh well. Sadly, this doesn't seem possible. It was worth a chat about. Thank you to everyone for your help, and insight.

06 August 2018, 11:38	#34
nidge Registered User Join Date: Apr 2018 Location: UK Posts: 2	Interseting discussion, a pity the Pi idea could not be done

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