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Chuck(G)
May 24th, 2010, 09:43 AM
This is just something that I'm tossing out for comments.

After going through the forum listings and looking at the trouble that people have trying to get a bootable SCSI disk going, I wonder if it might be of interest to anyone to start an 8-bit SCSI controller project?

It could be done fairly economically by using a modern microcontroller instead of one of the legacy SCSI interface chips. ASPI support for other devices might even be a possibility.

The design would probably be not more than 5 or 6 ICs, tops.

Thoughts? Or is SCSI too much of a dead horse?

mbbrutman
May 24th, 2010, 10:04 AM
I am definitely interested in SCSI interfacing - SCSI has been reliable for me across many different machines. However, doing the equivalent of a new SCSI chipset from scratch seems daunting. Are you thinking about patterning the microcontroller code after an existing chipset?

On a related topic, I've also seen your posts about the old NCR chipset on classiccmp - I'd like to get the application notes.

Unknown_K
May 24th, 2010, 10:07 AM
8 bit SCSI would be more useful to me then the IDE card (which I did buy), but would probably be more work to design.

Chuck(G)
May 24th, 2010, 10:19 AM
The electrical part of SCSI is pretty simple; most of the work is in the programming. Electrically, I don't think SCSI is any more complicated than IDE.

Minerva10210
May 24th, 2010, 11:36 AM
What kinds of drives would one hope to support with this card? I take it LDV drives with backplanes would be taking it too far? :D :P

I am a bit in the dark with older SCSI tech, so to me it does not make too much sense, what benefit would the SCSI have over the XTIDE project? Especially looking at drive sizes (storage size...) SCSI and IDE both have comparable storage?

Enlighten my ignorant side please ;)

Old Thrashbarg
May 24th, 2010, 02:34 PM
Given that there are already a few (fairly) commonly available 8-bit SCSI controllers out there, I don't know if it's really worth the effort to completely reinvent the wheel. The thing with the XTIDE project, is that it brings functionality that didn't previously exist, or was extremely rare: AT IDE on an XT bus. The SCSI guys, me included, already have some semi-workable options... the IDE guys didn't.

It would, however, be nice to have a working BIOS to use with the most common SCSI cards, to fix some of the niggling little bugs. For example, on my T130B, I'd really like not to have to swap the CPU for a V30 to get it to work reliably (especially on my particular machine, since the EMS card won't work with a V30), and also to get support for larger drives. Having a good BIOS floating around would also allow the use of the cards that didn't come with a BIOS installed (the majority of 'em?)... just burn the new one to chip and plug it in. Just a thought...

Chuck(G)
May 24th, 2010, 02:36 PM
I was thinking single-ended SCSI-I type of interfacing. If you want to do something else, you can buy a converter. :)

There are SCSI peripherals (e.g. tape drives) that simply have no comparable IDE version. There is also a standard API (ASPI) for drivers. It also was the case in the old days (don't know about now) that SCSI drives were generally built better (and cost more) than MFM/IDE drives.

My other thought on this was if there was the SPI lines from the uC uncommitted, an SD card interface could be added to take care of your hard disk needs. It seems such a waste to put just an SD card interface on an ISA card--so one might as well add something useful like SCSI.

k2x4b524[
May 24th, 2010, 03:55 PM
I would buy one of these cards, or the bios, if this one came to fruition, my TMC-850-MEX doesn't like ANY of my drives..

Mike Chambers
May 24th, 2010, 04:10 PM
ack.. SCSI. my arch nemesis.

Chuck(G)
May 24th, 2010, 04:11 PM
Given that there are already a few (fairly) commonly available 8-bit SCSI controllers out there, I don't know if it's really worth the effort to completely reinvent the wheel. The thing with the XTIDE project, is that it brings functionality that didn't previously exist, or was extremely rare: AT IDE on an XT bus. The SCSI guys, me included, already have some semi-workable options... the IDE guys didn't.

In the range of bootable 8 bit controllers that I've seen, there's the Seagate ST01 (slow and very quirky), Trantor T128 and T130 (also quirky) and the Future Domain TMC-850 (not the most available one). The DTC 3250 and a hanful of others could boo t, but I haven't seen one offered for a very long time.

Unknown_K
May 24th, 2010, 05:29 PM
The 8 bit SCSI are hard to find and expensive if you do find one. I was lucky enough to get a TMC-850 without a BIOS chip, soldered in a BIOS and support chip to get a bootable card. Normally they are $50+ which is more expensive then the XT IDE card.

Old Thrashbarg
May 24th, 2010, 06:15 PM
My T130B was $15, and I bought it a couple weeks after I passed on one for $25, both found on eBay within the last year, and I've run across a couple since then, too.

Yeah, they're not super common, the TMC-850 being one of the less common models, but there's also not a whole lot of people looking for them. Probably even fewer now that the XTIDE project is going.

Chuck(G)
May 24th, 2010, 06:40 PM
Well, the thought was to make an SD-card interface adapter for the 8 bit ISA bus, but that leaves a bunch of extra processing power doing nothing. USB host interface (UHCI) is a nightmare if you expect it to be absolutely general (i.e. be able to plug hubs, keyboards, scanners, hard disks, etc. into it). While you might succeed in making a host just to support a USB flash drive, I'd much rather have the SD card.

We've already got IDE, so that leaves SCSI.

Just looking for some ideas...

Old Thrashbarg
May 24th, 2010, 07:12 PM
Yeah, the SD card interface would be kinda cool, although I'm not really sure what practical advantage it would give over a compact flash card running on IDE. Is there a particular reasoning behind it, which I'm overlooking?

wmmullaney
May 24th, 2010, 07:42 PM
It would just be a fun summer project ;)

Would you be able to support floppy and and cd burning drives as well?

Chuck(G)
May 24th, 2010, 07:58 PM
Floppy, as in Teac FD-235HS? Those are pretty uncommon (I have one). I don't see why not, given the right drivers (ay, there's the rub!) I'll probably go as far as an ASPI driver and boot ROM for hard drives and leave everything else to the user's imagination ;).

Did anyone ever make CD-ROM burning software for a PC XT?

(P.S. If you'd like to see something ridiculous, check out the price on this FD235HS drive (http://www.partstore.com/Part/Teac/TEAC/FD235HS1211.aspx?s=froogle&CID=froogle). Supposedly, they're still available from Teac.)

NobodyIsHere
May 25th, 2010, 03:12 AM
Hi! Well, if you want SD on ISA bus that would be essentially an ISA version of the N8VEM PropIO board. An ISA board with a Propeller uC on it and a uSD socket. It *appears* to be a pretty simple conversion although it would require programming on the PC *and* Propeller sides.

Anyway, if the 8 bit SCSI ISA board ever gets traction I'm game for a PCB. Right now is not a good time but eventually when things calm down a bit.

Thanks and have a nice day!

Andrew Lynch

Raven
May 25th, 2010, 05:14 AM
I have no use for a SCSI controller (unless it supported the full suite of external SCSI stuff), but the SD card interface... Might I make the comment that it would be best if the SD card was mounted with a slot through the rear of the bracket, so that it can be externally changed out like a card reader. Basically I'd use it like a card reader with reboots between swaps.

NobodyIsHere
May 25th, 2010, 06:06 AM
Hi! Keeping consistent with Chuck's idea, the Propeller uC has 32 possible GPIO pins. The uSD interface requires 4 IIRC and SCSI-1 requires 18, I think. The rest of the pins on the connector are grounds and power. The Propeller is a 3.3V device which is not a problem but the GPIO pins would require level conversion and/or pass through a bus transceiver/buffer to the SCSI interface.

There two main kinds of SCSI interface connectors I think would be most useful; the 50 internal dual row header for ribbon cables and the 25 pin external DB-25. Assuming the Propeller needs 2 GPIO pins for a EEPROM there are still 30 GPIO pins remaining with uSD needing 4 and the SCSI needing 18.

Where things get tough is the bus interface for the Propeller required several (13?) pins itself such as D0-8, /CS, /RD, /WAIT, A0 & A1. I think a Propeller ISA to SCSI solution is at least possible although wedging in a uSD interface may require either a second Propeller, switching logic, or using a different uC with more GPIO pins.

I am sure there are ARM, PIC, or other uC solutions that would work. Probably something in PLCC or DIP that keeps relatively easy hobbyist buildability without resorting to SMT packages.

Just my $0.02. Thanks and have a nice day!

Andrew Lynch

Raven
May 25th, 2010, 07:47 AM
All of my external SCSI devices use Centronix 50, I don't have a single DB25 device myself (other than SCSI ZIP drives). Perhaps a poll is in order about this one - or offer an adapter or both connector options if it's a simple wiring matter?

Chuck(G)
May 25th, 2010, 09:29 AM
Hi Andrew,

I was thinking about a 68-pin QFP for the uC--it's not hard to solder the coarse pitch devices and it means fewer holes to drill. I don't know if any of the 8051-family controllers are available in 68 or 84-pin PLCC, but that might be another option and they're almost certainly fast enough. RAM isn't an issue, as most early SCSI controllers had very little (256 bytes or less).

Raven,

The 50-pin Amphenol "blue ribbon" connectors are a nightmare for ISA cards. The connector body is very wide in comparison with the width of the bracket, so horizontal positioning above the PCB is a real issue--and then there is the problem of the bail clips getting stuck in the case slot (it happened a lot). I'd much rather use either the standard 50-conductor SCSI HD connector or a DB-25 (Apple and others used this quite often; it's more than adequate for SCSI-I, is cheap, widely available and very robust.

lutiana
May 25th, 2010, 10:14 AM
Well, the thought was to make an SD-card interface adapter for the 8 bit ISA bus, but that leaves a bunch of extra processing power doing nothing. USB host interface (UHCI) is a nightmare if you expect it to be absolutely general (i.e. be able to plug hubs, keyboards, scanners, hard disks, etc. into it). While you might succeed in making a host just to support a USB flash drive, I'd much rather have the SD card.

We've already got IDE, so that leaves SCSI.

Just looking for some ideas...

I also don't have much use for SCSI, but the idea of a ISA USB Mass Storage card for an XT (or any DOS) machine is intriguing, and strikes me as very useful and convenient.

So why not an ISA card with a USB port for mass storage support only (not general USB). This would open up quite a few options for storage including external hard drives, USB thumb drives, card readers etc; anything that is in the USB Mass Storage device class really. They would all be easily removed and plugged into another (modern) machine.

You could also build in some sort of floppy disk emulation for memory cards as well, that would make it even more useful.

EDIT:

According to Wikipedia, the USB Mass Storage Device class (http://en.wikipedia.org/wiki/USB_mass-storage_device_class) includes:


external magnetic hard drives (http://en.wikipedia.org/wiki/Hard_drive)
external optical drives, including CD (http://en.wikipedia.org/wiki/CD) and DVD (http://en.wikipedia.org/wiki/DVD) reader and writer drives
portable flash memory (http://en.wikipedia.org/wiki/Flash_memory) devices (http://en.wikipedia.org/wiki/USB_flash_drive)
adapters bridging between standard flash memory cards (http://en.wikipedia.org/wiki/Memory_card) and a USB connection
digital cameras (http://en.wikipedia.org/wiki/Digital_camera)
various digital audio players (http://en.wikipedia.org/wiki/Digital_audio_player) & portable media players (http://en.wikipedia.org/wiki/Portable_media_player)
Card readers (http://en.wikipedia.org/wiki/Card_reader)

That is a very nice list of usable and cheaply available storage for your XT or even AT DOS machines :D

NobodyIsHere
May 25th, 2010, 10:19 AM
Hi Chuck,

I count 30-31 minimum GPIO pins for a uC solution. Sure a 64 QFP would work but probably a 40 pin PIC or AVR plus some TTL glue logic for a SCSI-1 only option.

I agree with you on the connector assessment. Definitely the 50 pin dual row header for internal SCSI drives and DB-25 for external. Much easier to work with and I am fairly sure the footprints exist in the EDA libraries. I suspect the big 50 external connector would require a tricky custom footprint.

Still the hard part, as with any project, is the PM and SW development. I suspect if we needed hardware we could whip up a hardware prototype in week or two by basically marrying up an AVR/PIC (QFP or DIP) to the XT-IDE board frame work and scooping out the IDE guts. Send off to a prototype fab house and presto you've got boards. Hardware -> easy, PM and SW -> much harder.

Thanks and have a nice day!

Andrew Lynch

Chuck(G)
May 25th, 2010, 02:40 PM
Hi Andrew,

A 40 pin DIP might be possible, but I'll have to check that one out. But there are other alternatives that give a bit more breathing room. The Atmel AT89C51ED2, for example, can be had in a 68 pin PLCC, so you get through-hole and 48 I/Os--and it's 5V and up to 60MHz clock. DigiKey lists it for $11 Q1. So that may be an option.

Lutiana,

Writing the USB stack for all of the various storage devices is a little more than I want to bite off. And sure as tomorrow, someone will want support for floppy drives and 2TB hard drives too...

If you really want USB support for flash drives, you're best bet is the Vinculum VDRIVE2 (http://vinculum.com/documents/datasheets/DS_VDRIVE2.pdf) All you need is a level-shifter, such as a MAX232 to get to RS232 signal levels. About $25 in single quantities. I don't know what the extent of the device support past USB flash is, however.

lutiana
May 25th, 2010, 03:01 PM
Writing the USB stack for all of the various storage devices is a little more than I want to bite off. And sure as tomorrow, someone will want support for floppy drives and 2TB hard drives too...


Ahh, well I was making the suggestion from the stand point of one who has no idea what would be involved with its construction.

FWIW I was more envisioning something with a BIOS that handles all the IO to the storage medium and simply shows up as a drive letter in the OS (no driver needed). The beauty of a home brew thing like this is you can specify the limitations, and if someone else wants something that goes beyond it, they can modify it themselves. I would have suggested limiting it to just a few type of mass storage devices and sizes to keep it simple, but expandable if needed.

Chuck(G)
May 25th, 2010, 04:31 PM
FWIW I was more envisioning something with a BIOS that handles all the IO to the storage medium and simply shows up as a drive letter in the OS (no driver needed). The beauty of a home brew thing like this is you can specify the limitations, and if someone else wants something that goes beyond it, they can modify it themselves. I would have suggested limiting it to just a few type of mass storage devices and sizes to keep it simple, but expandable if needed.

Then the Vinculum DRIVE2 is definitely what you want--it handles the filesystem (FATx) management; you just shoot it commands and data.

As far as "modifying it for themselvs", that seems not to be the rule here. I released the code for the AT-XT keyboard converter; but no one wants to tackle the questionably-useful XT-AT variant, even though the board's done and most of what you need (e.g. how to send data out a PS/2 keyboard port) is already coded. Everyone seems to be waiting for me to do the work, even though I have no use for such a gizmo (I like my PS/2 model Ms, thank you).

NobodyIsHere
May 26th, 2010, 02:31 AM
Hi Andrew,

A 40 pin DIP might be possible, but I'll have to check that one out. But there are other alternatives that give a bit more breathing room. The Atmel AT89C51ED2, for example, can be had in a 68 pin PLCC, so you get through-hole and 48 I/Os--and it's 5V and up to 60MHz clock. DigiKey lists it for $11 Q1. So that may be an option.



Hi Chuck! Definitely, that sounds like a winner! Plenty of GPIO, fast, cheap, and through-hole construction. Very nice indeed.

In my mind, I picture this design to be a card much like the XT-IDE. Keep the BIOS circuit, bus transceiver/buffers, and IO decoder basically intact. The uC drives the SCSI interface with OC inverters (74LS06) driving the outputs and inverters (74LS14) on the inputs. Feed the IO decode /CS, D0-8, /IORD, A0-1, to the uC to tie it to the ISA bus with a couple of buffers in between (74LS244s).

Is that what you are thinking? It certainly sounds possible to me. Again, the hard part is the PM and SW especially on the uC side. We have some code for the Propeller to make it act like an IO device on the Z80 bus. That might be semi-helpful but given the differences with the AT89C51 it is probably closer to total rework.

Unless I am missing something, I am estimating ~16 GPIO left over. Since the AT89C51 has its own internal Flash there wouldn't be any need for uC external memory. However, you'd probably want some form of in circuit reprogramming for updates.

If this is consistent with your ideas, I can make a schematic as a starting point so we can discuss further. It'll have to wait a few days until we get some S-100 SMB prototype and the S-100 IDE board issues fixed though.

Just my $0.02. Thanks and have a nice day!

Andrew Lynch

aitotat
May 26th, 2010, 08:05 AM
I have no need for SCSI controller but a multi purpose card with programmable micro controller would be really nice.

Here are some ideas how the micro controller could be used:

Midi controller. It is really hard to find a MPU-401 controller with intelligent mode support. I haven't done any research but i think the hardware interface is simple so the intelligent mode features could be done in software.
DMA controller. Memory to memory transfers or maybe it could transfer data between XTIDE and memory. It should speed up transfer rates since using two 8-bit ports is slow with CPU (the micro controller would need to be faster than the CPU).
EMS card or maybe as a disk cache so smartdrive would not be needed.


I think the (SCSI) card should be designed as a 16-bit ISA card that would also work on a 8-bit slot. Anyway, please use at least 16 kiB EEPROM. Or two or more (some optional) 8 kiB EEPROMs.

8 kiB is too small for XTIDE since i have lots of ideas that just won't fit there:

HD floppy support
RTC support for XTs so no software would be needed
Support for different keyboard layouts (would save memory since keyb.com would no longer be needed)
Build-in EEPROM flasher
Simple hard disk utilities (diagnostics, partition, etc)

Chuck(G)
May 26th, 2010, 08:38 AM
There are other ways to speed up data transfer from the XTIDE, but they would require a redesign; you'd probably want to take that up with Hargle. As far as MIDI, consider that you can take a plain old IBM serial card with current-loop interface and change the crystal to get the same thing. Before MIDI cards became widely available for the PC XT, this was a common dodge.

Andrew, I'm not even to the back-of-the-envelope stage, but I think there's definitely something to work with here.

dorkbert
May 26th, 2010, 08:59 AM
Don't mean to rain on your parade, but SCSI is tough. Your output buffer need to be able to drive a 5 MHz bus through a maximum of 6 meter long cable (which are typically unshielded ribbon cables) to meet spec for SCSI 1, 3 meters for fast SCSI. Don't get me wrong, it can be done. I just don't think it's as simple as you're thinking of.

Raven
May 26th, 2010, 09:22 AM
I also don't have much use for SCSI, but the idea of a ISA USB Mass Storage card for an XT (or any DOS) machine is intriguing, and strikes me as very useful and convenient.

So why not an ISA card with a USB port for mass storage support only (not general USB). This would open up quite a few options for storage including external hard drives, USB thumb drives, card readers etc; anything that is in the USB Mass Storage device class really. They would all be easily removed and plugged into another (modern) machine.

You could also build in some sort of floppy disk emulation for memory cards as well, that would make it even more useful.

EDIT:

According to Wikipedia, the USB Mass Storage Device class (http://en.wikipedia.org/wiki/USB_mass-storage_device_class) includes:


external magnetic hard drives (http://en.wikipedia.org/wiki/Hard_drive)
external optical drives, including CD (http://en.wikipedia.org/wiki/CD) and DVD (http://en.wikipedia.org/wiki/DVD) reader and writer drives
portable flash memory (http://en.wikipedia.org/wiki/Flash_memory) devices (http://en.wikipedia.org/wiki/USB_flash_drive)
adapters bridging between standard flash memory cards (http://en.wikipedia.org/wiki/Memory_card) and a USB connection
digital cameras (http://en.wikipedia.org/wiki/Digital_camera)
various digital audio players (http://en.wikipedia.org/wiki/Digital_audio_player) & portable media players (http://en.wikipedia.org/wiki/Portable_media_player)
Card readers (http://en.wikipedia.org/wiki/Card_reader)

That is a very nice list of usable and cheaply available storage for your XT or even AT DOS machines :D

I am so on board with this idea.. While we're throwing out ideas, let's make it have an internal USB port and an external USB port(s) and make it bootable, so you can replace the HDD with a USB device like a jump drive internally. :D

Chuck(G)
May 26th, 2010, 09:54 AM
Don't mean to rain on your parade, but SCSI is tough. Your output buffer need to be able to drive a 5 MHz bus through a maximum of 6 meter long cable (which are typically unshielded ribbon cables) to meet spec for SCSI 1, 3 meters for fast SCSI. Don't get me wrong, it can be done. I just don't think it's as simple as you're thinking of.

Transceivers are typically 7438-type sinking 48 ma. But it's been done with less. Consider the ST01 or T130B--no external drivers at all, just the on-chip open-drain ones on the 53C400 or its TI clone. Hell, the ST01 doesn't even have terminators on-board. No more or less difficult than doing a lot of other protocols, including MFM.

Here's a sample of something similar done with AVR micros (http://micha.freeshell.org/ramdisk/index.php)

For my reference, I'm using the NCR "5380 SCSI Interface Chip Design Manual". The 5380 was a SCSI-1 stalwart chip used in many designs.

Tupin
May 26th, 2010, 10:24 AM
I have a few SCSI drives, but a USB ISA card would be cool...

Chuck(G)
May 26th, 2010, 12:19 PM
You don't need me for a USB card. Just buy a vinculum DRIVE2 module, and hook it to an RS-232-to-TTL level converter. (http://www.piclist.com/techref/io/serial/ttl-rs232.htm). Just pass ASCII commands over your serial port.

Raven
May 26th, 2010, 12:26 PM
You don't need me for a USB card. Just buy a vinculum DRIVE2 module, and hook it to an RS-232-to-TTL level converter. (http://www.piclist.com/techref/io/serial/ttl-rs232.htm). Just pass ASCII commands over your serial port.

This implies we're all really good with ASM or C and DOS driver programming. :P

Chuck(G)
May 26th, 2010, 12:45 PM
This implies we're all really good with ASM or C and DOS driver programming. :P

You can talk to a com port in BASIC--no drivers required if all that you want to do is read and write a flash drive. Read the firmware guide (http://www.vinculum.com/documents/fwspecs/UM_VinculumFirmware_V205.pdf). It's a no-brainer.

Raven
May 26th, 2010, 05:46 PM
Oh I see - I had assumed that it was a "dumb" device, not having interfacing logic, which would make things much harder. That would allow you to write a program to push and pull files to/from a flash drive, but it wouldn't allow it to show up as a natural drive letter in DOS - or am I wrong?

Chuck(G)
May 26th, 2010, 09:26 PM
Oh I see - I had assumed that it was a "dumb" device, not having interfacing logic, which would make things much harder. That would allow you to write a program to push and pull files to/from a flash drive, but it wouldn't allow it to show up as a natural drive letter in DOS - or am I wrong?

As long as you didn't need to boot from it, you could always implement it as a network redirector in DOS. Musch easier than a device driver.

lutiana
May 26th, 2010, 09:31 PM
As long as you didn't need to boot from it, you could always implement it as a network redirector in DOS. Musch easier than a device driver.

Ahh, well my USB Storage idea was to have a completely bootable DOS volume on a USB mass storage device, which is easy to swap out. But the more I think about the more I think it may not be all that great, or at least worth the trouble to make it.

NobodyIsHere
May 27th, 2010, 02:51 AM
Hi! USB on an ISA card is possible. As Chuck said, the Vinculum parts would work on a card like the XT-IDE as would a lesser capable but still USB 1.1 AVR USB

http://www.obdev.at/products/vusb/index.html

However, the tough part remains the PM and SW effort needed to make something happen. I think the hardware is the easy part. With my backlog of other projects there is no way I am taking on the SW for this so we'll need some motivated talent. We'd also need a hardware prototype to get started developing the software. The downside of the Vinculum is the parts are not cheap!

The design could be implemented in many ways. Either write specific uC code to access the device by an IO port directly or by some interface logic. The Vinculum supports SPI "out of the box" so it might be easier to use 8 bit IO input and an output ports to control the device. Possibly use an 8255 to do the same thing. Just as starting point, I'd consider something like this just because I like 8255s although simplified further.

http://engr.nmsu.edu/~etti/4_1/4_1s.html

I used something akin to this method to control the DS1307 RTC on the N8VEM SBC. It is an IO decoder with 74LS574 8 bit latch for output and a 74LS125 for input IIRC. The circuitry is pretty simple. I'll be glad to help with the PCB if the project gets rolling. It isn't going to happen by itself though so feel free to jump in.

Thanks and have a nice day!

Andrew Lynch

PS, for prototypes there are many ways to go. IMO, the two most practical methods are wire wrap using the Jameco ISA prototype board or just going straight to a prototype PCB using a "barebones" or "33each" prototype PCB. Given the time constraints the prototype PCBs are most appealing to me. Getting a batch of "33each" PCBs costs about $150 and saves a lot of time especially for relatively low risk prototypes. There would be enough boards for 4 SW developers and me (HW verify). With shipping that'd be about $40 per unit plus parts costs.

Chuck(G)
May 27th, 2010, 07:32 AM
Hi Andrew,

The V-USB projects are all device-side, not host-side. Host-side is quite a bit more complicated and all AVR implementations that I've seen of host mode use an AVR-USB chip and a pile of software. For example, here's an app note from Atmel. (http://www.atmel.com/dyn/resources/prod_documents/doc8229.pdf)

Maxim also makes a host controller chip (http://www.maxim-ic.com/app-notes/index.mvp/id/3782) that some have used.

The PIC 24F series also can handle host mode and Microchip has a code example with a pen drive interface.

There are a couple of ARM7 USB host implementations as well as many ARM9 hosts. But everything that I've just discussed is SMT and involves more code than I want to think about.

NobodyIsHere
May 27th, 2010, 07:55 AM
Hi Chuck! A whole bunch of complicated software required and SMT certainly makes it less appealling.

However as you said earlier Vinculum offers a couple of host mode capable DIP packages that would work with the ISA prototype concept. My main reason to avoid SMT for projects like this is many hobbyists are eliminated by using non-DIP construction. Part of my intent for advocating home brew computer is for hobbyists to get involved and build the board themselves! By using SMT in effect, you or me or whomever turns into a board assembly house soldering on the parts for everybody. I don't have time or patience for it so thats a non-starter.

I'll work on the schematics, PCB layout, prototype boards, and manufactured PCBs but not kit assembly or board assembly. I think home brew computer hobbyists have to use the soldering iron (or equivalent) or they are missing something essential.

Thanks and have a nice day!

Andrew Lynch

Chuck(G)
May 27th, 2010, 09:05 AM
Hi Andrew, I think the Vinculum VDIP1 (http://www.farnell.com/datasheets/63955.pdf) would be perfect for a hobbyist application in that it fits in a 24 pin DIP socket. The only barrier that I can see is its relatively high price (about $25 from Newark). But this is outside of what I'm willing to do for a simple ISA project.

lutiana
May 27th, 2010, 06:25 PM
Hi! USB on an ISA card is possible. As Chuck said, the Vinculum parts would work on a card like the XT-IDE as would a lesser capable but still USB 1.1 AVR USB

Yep, thats why I said its probably not worth it to make a whole ISA card to do it. The SCSI idea would be a whole lot more useful. It would be nice to put one of my external JAZ drives onto my XT.

NobodyIsHere
May 28th, 2010, 02:31 AM
Hi! Either the Vinculum VDIP USB ISA project or the SCSI ISA project seem fine to me. From my perspective they seem about the same complexity and effort. I'm willing to help out with a schematic, PCB layout, prototype boards, and manufactured PCBs if/when either or both projects take off.

Actually, I am considering an ISA prototyping board based on the designs posted earlier. They look really handy for projects like this. Basically an 8 bit ISA card with basic buffers, bus transceivers, simple IO decoders, an 8255, and an external port would be tremendously helpful in all sorts of projects.

Thanks and have a nice day!

Andrew Lynch

sombunall
May 28th, 2010, 03:30 PM
So if somebody wanted to use the Vinculum VDIP for a MFM to USB project they would have to add 128K of SRAM to capture a single track (83K) and also a timer with capture mode? I mean, it would be better for both projects to try to use the same chip if possible?

Chuck(G)
May 28th, 2010, 04:00 PM
So if somebody wanted to use the Vinculum VDIP for a MFM to USB project they would have to add 128K of SRAM to capture a single track (83K) and also a timer with capture mode? I mean, it would be better for both projects to try to use the same chip if possible?

I'm not following you. An MFM controller (or IDE, or pen drive) would be a device-side (i.e. slave) controller. The Vinculum is a host-side (i.e. master) controller. A very different kettle of fish, methinks.

gerrydoire
May 28th, 2010, 04:13 PM
ack.. SCSI. my arch nemesis.

Slay the SCSI monster!!!

digger
May 29th, 2010, 02:43 AM
Although redesigning an 8-bit ISA SCSI controller would undoubtedly be an interesting and educational project, I would be more interested in the development of an improved version of the XTIDE card with optional DMA and hot-swap/eject support. Reading the XTIDE wiki, it would indeed seem that such features are already planned for revision 2 of the PCB design. Awesome. :) Not only will we not have to start from scratch since we already have a first revision XTIDE design that we can now improve on, the IDE interface is still the most interesting interface to concentrate on, since cheap (< $10 ) IDE converters can already/still be found for CompactFlash, SD, and SATA.

And besides, there are already some 8-bit ISA SCSI controllers out there. The real problem is the lack of proper (ASPI) drivers for them. That is also the case for the Rancho RT1000 card that I really wanted to use with an internal ZIP drive or CDROM player, but couldn't get to work, because the ASPI drivers didn't run on the V30 XT I tried it on. :( So as someone else already proposed here, it would make more sense to develop open source BIOSes and ASPI drivers for the existing models, than to reinvent the wheel outright.

Chuck(G)
May 29th, 2010, 08:35 AM
And besides, there are already some 8-bit ISA SCSI controllers out there. The real problem is the lack of proper (ASPI) drivers for them. That is also the case for the Rancho RT1000 card that I really wanted to use with an internal ZIP drive or CDROM player, but couldn't get to work, because the ASPI drivers didn't run on the V30 XT I tried it on. :( So as someone else already proposed here, it would make more sense to develop open source BIOSes and ASPI drivers for the existing models, than to reinvent the wheel outright.

I'm sure you have complete internal documentation for those legacy SCSI cards. You do, don't you? So you can get cracking on an ASPI driver.

8-bit SCSI cards that actually boot larger (8 GB+) hard drives are very uncommon. Do you know of any cheap ones?

digger
May 29th, 2010, 11:25 PM
I'm sure you have complete internal documentation for those legacy SCSI cards. You do, don't you? So you can get cracking on an ASPI driver.

You mean the Rancho RT1000 I mentioned? I couldn't find any downloads for that card recently (whether drivers or hardware documentation). At least some years ago, I could still download legacy DOS drivers somewhere. Now, I can't find those anywhere anymore. I did save the drivers I had downloaded back then on a floppy, but it got partially corrupted, so some of the files may have been damaged. :( If anybody can help me with either software or documentation, I would much appreciate it. Perhaps someone knows about a generic ASPI driver that works with most 8-bit SCSI BIOSes out there? That could perhaps also work...?

Oh well... I've but my hope in the XTIDE project now. :)

Chuck(G)
May 30th, 2010, 07:03 AM
If anybody can help me with either software or documentation, I would much appreciate it. Perhaps someone knows about a generic ASPI driver that works with most 8-bit SCSI BIOSes out there? That could perhaps also work...?

Oh well... I've but my hope in the XTIDE project now. :)

Good luck with Rancho. They sampled us a parallel-to-floppy adapter years ago. They refused to provide any sort of technical documentation, even though there was the prospect of substantial sales if we could get it to work in our application. I still have the adapter and their drivers, but nothing else.

And good luck with getting your DDS or DLT tape drives or your scanner going with the XTIDE.

digger
May 30th, 2010, 01:01 PM
And good luck with getting your DDS or DLT tape drives or your scanner going with the XTIDE.

I get your point, but fortunately, that is not going to be an issue for the vintage computer I plan on equipping with an XTIDE card. ;) ...Although it would be an interesting project to get ATAPI tape streamers working with the XTIDE controller, once CD-ROM has been made to work.