Re: self contained home computer project ideas

[yoda <yo...@r2d2.org>]

Hi James

As much as I love the propeller, I think an XMOS chip will work
better.  There is already code to do SPI and I2C for the XMOS.  We
will have to layer that FAT stuff on top but should be a straight
forward port of the code.  The only concern I have is video, I have
not found any general purpose VGA code yet.   There is some sprite
based code - maybe that can be enhanced.

Anyways I have a developer's kit coming in the mail now for XMOS so
hopefully in a week or so I will be able to better assess its
capabilities.

On Oct 27, 11:23 pm, James Moxham <mox...@internode.on.net> wrote:
> I am thinking that the Z180 could spawn all sorts of new boards,
> includnig the small one you mention.
>
> SD card is something I'm still not clear about - the one I understand is
> the propeller because I know it can do fat16 and fat32. Can the juha
> code do fat32?
>
> Looking at the propeller code, it is quite large, and hence I'm not
> entirely sure how this fits into CP/M memory. And hence into MP/M
> memory. I guess I don't want to put the bank much lower than 0xB000 as
> I've already come up against not having enough memory for a rather large
> sbasic program.
>
> The xmos sounds very good. Is the code for sd card and spi and keyboard
> in pre-written 'objects', like the propeller code?
>
> Every time I look at my circuit I think there are far too many latches!
> I'm looking at eprom again, and I see you are looking at latches. Maybe
> in a week we will swap?!  As a general question, I wonder what is a
> minimum bootloader that avoids an eprom? I once did it with a printer
> port, a 4040 and a buffer that you tristated when it was ready to run,
> plus held reset low. I've toyed with the idea of a couple of HC595s -
> less control pins.
>
> The Z180 has an eprom, but based on the propeller circuits, it may be
> easier to use the eprom just to get enough code to get some data off an
> sd card. Then you can load boot disks etc.
>
> Great to see the Z180 board coming to life so quickly!
>
> Cheers, James
>
> On 27/10/2010 4:22 PM, yoda wrote:
>
>
>
> > Hi James,
>
> > I am thinking the XMOS might be an appropriate super I/O chip.  My
> > only concern, I am not seeing much about good video support yet.  I am
> > pretty sure it can do the video but all I have found so far is all
> > sprite based and not anything like emulating vga text level.   I think
> > a very minimal chip count SBC can be created with the z8s180, ram, and
> > xmos chip.  The xmos can easily do spi for the SD and handle keyboard,
> > mouse as well.  If we restrict DMA to the lower page of memory we can
> > probably create a nice DMA support interface with 8 date, 8 control,
> > that still gives us 20 I/O lines to play with.
>
> > I am traveling at the moment but am going to order a prototyping
> > system from Sparkfun now to start looking at what it will take to make
> > the XMOS a super I/O chip for the SBC. It definitely has some
> > advantages over the propeller operating at 400MHz - we should not have
> > to play with the /WAIT to make the interface work.
>
> > Dave
>
> > On Oct 27, 12:36 am, James Moxham<mox...@internode.on.net>  wrote:
> >> That sounds a plan if you are limited for space.
>
> >> Maybe think about what would be the simplest interface for video.
>
> >> I was pondering this, thinking about the xmos vs the propeller as a
> >> video chip. Say you dedicated such a chip to video and used all of its
> >> internal ram as a screen buffer. Then you only need to send changes to
> >> pixels or text. So the data transfer bus can be slower. Then it doesn't
> >> matter which chip you use.
>
> >> I was thinking of serial. Or maybe a 2 line SPI type of interface, eg
> >> clock and data. The latter would be timing independent.
>
> >> Then you could think about being flexible with the display - it can be
> >> the xmos, or the propeller, or something else.
>
> >> Did you have room for onboard video?
>
> >> Cheers, James
>
> >> On 27/10/2010 10:15 AM, Andrew Lynch wrote:
>
> >>> Hi James!  Thanks!  I've found that the prototype board manufacturer has a
> >>> limitation of 60 square inches not the 100 square inches I was assuming in
> >>> the prototype.  The current design has already filled the board and it still
> >>> does not have the video which is essential to a home computer.
> >>> As the project evolves I've been thinking more about design goals and what
> >>> are priorities.  The computer should give some immediate feedback on power
> >>> up to display video and interact with the keyboard so that is important.  In
> >>> terms of priority, the IO is paramount as there are many CPU choices we can
> >>> use.
> >>> The current design is going to be scaled back significantly to fit in the
> >>> prototype PCB constraints.  My plan is to start over on this and try the SBC
> >>> V2 + SCG + keyboard + timer + SD approach and see if that will fit.  We can
> >>> convert the design to Z8S180 at a later stage.
> >>> Thanks and have a nice day!
> >>> Andrew Lynch
> >>>> -----Original Message-----
> >>>> From: n8...@googlegroups.com [mailto:n8...@googlegroups.com] On Behalf Of
> >>>> James Moxham
> >>>> Sent: Tuesday, October 26, 2010 3:14 AM
> >>>> To: n8...@googlegroups.com
> >>>> Subject: Re: [N8VEM: 8129] Re: self contained home computer project ideas
> >>>> This is so exciting! I see on another post that this chip goes to 33Mhz.
> >>>> That is going to be quite amazing. Will it require different 'glue'
> >>>> chips to HC or HCT?
> >>>> Cheers, James
> >>>> On 26/10/2010 9:57 AM, lynchaj wrote:
> >>>>> Hi Max!  Thanks!  I updated the schematic and added an initial PCB
> >>>>> layout.  The board is incomplete but still enormous.  I started with a
> >>>>> 10"x10" board assuming absolute worst case it could not be that
> >>>>> large.  I still need to add the FDC section, video, and audio and it
> >>>>> is about 60% full.  There are several pins on the CPU that are NC
> >>>>> because I am not sure what to do with them.
> >>>>> Please take a look and send me any notes.  The schematic does not pass
> >>>>> ERC yet with 15 warnings which are mostly disconnected pins.  I
> >>>>> started with two PIOs but changed to 2 PPIs (8255s) to support
> >>>>> printer, keyboard, and mouse ports and the parallel utility port from
> >>>>> the SBC V2.  There is still one PIO for the SD interface with some
> >>>>> spare pins left over.
> >>>>> Thanks and have a nice day!
> >>>>> Andrew Lynch
> >>>>> On Oct 24, 10:09 pm, Max Scane<mjs...@gmail.com>     wrote:
> >>>>>> Hi Andrew,
> >>>>>> That is a really good start.
> >>>>>> the TXS,RXS and CKS are used for the Clocked Serial port which could be
> >>>> used
> >>>>>> for a High Speed serial link.  Trouble is it is only Half Duplex.  I
> >>>> wonder
> >>>>>> if it could be used to drive the SPI on the SD Card?   I would just
> >>>>>> terminate it on headers for now.
> >>>>>> Cheers!
> >>>>>> Max
> >>>>>> On Mon, Oct 25, 2010 at 12:37 PM, lynchaj<lyn...@yahoo.com>     wrote:
> >>>>>>> Hi John!  Thanks!  OK, I think the Z8S180 is the way to go.  I started
> >>>>>>> a schematic just to jot down some ideas.  There are many areas I am
> >>>>>>> not familiar with so I'll need some help from you and Max and whoever
> >>>>>>> else is interested in designing this project.
> >>>>>>> I started with the SBC V2 and made modifications.  I've placed a
> >>>>>>> schematic draft in the new "home computer" folder on the N8VEM wiki
> >>>>>>>http://n8vem-
> >>>> sbc.pbworks.com/w/browse/#view=ViewFolder&param=Home%20C...
> >>>>>>> What I have so far is a Z8S180 CPU and some basic parts.  The
> >>>>>>> schematic part has to be updated since it is a Z180 in DIP format.  I
> >>>>>>> will convert it to the PLCC format and update the pin numbers.  There
> >>>>>>> are many pins I do not know what to do with.  Any suggestions
> >>>>>>> appreciated.
> >>>>>>> There is a 512KB Flash ROM (29F040) and two 512KB SRAMs.  The system
> >>>>>>> defaults after reset to ROM in 0-512 and can be swapped out for a SRAM
> >>>>>>> based on a /ROM_ENABLE configuration latch.  The upper 512KB is always
> >>>>>>> SRAM.
> >>>>>>> I removed the 8255 parallel port chip.  In its place I am using two
> >>>>>>> PIOs.  The first is dedicated to a printer port and the second
> >>>>>>> supports the PS/2 keyboard, mouse, and SD.  There are 4 spare pins
> >>>>>>> still.
> >>>>>>> The 16C550 serial port is gone.  It is replaced with the Z8S180 built
> >>>>>>> in dual serial ports.  The first one is straight forward.  The second
> >>>>>>> is a partial implementation.  Also there is a high speed synchronous
> >>>>>>> clock in, out, and receive.  I have no idea what to do with that.  I
> >>>>>>> definitely need some help with the serial ports.
> >>>>>>> I added the IDE port with the improvements to make sure /DIOR and /
> >>>>>>> DIOW are gated to the chip selects.  That dramatically improves
> >>>>>>> compatibility with drives such as WD, etc.
> >>>>>>> The memory page configuration latches are gone.  There is a major
> >>>>>>> update to the memory decoding logic and I am pretty sure it needs a
> >>>>>>> rework.  There are now four levels of logic to get to a RAM chip
> >>>>>>> select so it will have to be fixed.
> >>>>>>> I am keeping the ECB bus interface logic and buffering/transceivers
> >>>>>>> are basically the same.  Also the status LED is the same.
> >>>>>>> Don't take this schematic too seriously; it mostly me scratching down
> >>>>>>> notes before I forget them.  Once we get the basic logic and
> >>>>>>> infrastructure in place we can add in the video and audio from the
> >>>>>>> SCG.  I am also holding off on the floppy drive controller for the
> >>>>>>> same reason.
> >>>>>>> Thanks and have a nice day!
> >>>>>>> Andrew Lynch
> >>>>>>> On Oct 24, 11:15 am, John Coffman<john...@gmail.com>     wrote:
> >>>>>>>> Of the Z180 chips out there, I would lean toward the Z8S180.  It
> >>>> looks
> >>>>>>> like the most recent mask.  It looks like a nice challenge to make
> >>>> best use
> >>>>>>> of the Z180 memory mapping scheme.
> >>>>>>>> The Z8S180 DMA controller is very similar to the 80186/8 DMA
> >>>> controller;
> >>>>>>> so I think we are getting to know the plusses and minuses of the
> >>>> WD37C65
> >>>>>>> chip.  If I were doing a [floppy] DiskI/O board v2, I would use the
> >>>> chip,
> >>>>>>> but with an 8237, the DMA controller to which it is a better match.
> >>>> One
> >>>>>>> item that cannot be tested on the SBC-188 is whether the chip can be
> >>>> used
> >>>>>>> with external floppy motor control, like the DiskI/O board, and
> >>>> thereby
> >>>>>>> avoid the pitfalls of a non-8237 DMA controller.
> >>>>>>>> --John
> >>>>>>>> On 10/23/2010 05:49 PM, Andrew Lynch wrote:
> >>>>>>> --
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