update #3, the chook is silenced or the compact flash works

With a little bit of tweaking, some reverse engineering, wire, vero board and a magnifying glass, the microbee boots from flash.

Here’s how I built the hardware interface. ( note larger versions of all of the pics are available here )

Here is where the interface will connect the the 128k coreboard. Note the three holes near the front right of the 34pin floppy drive socket, next to the ’40’ on the overlay.

Solder the 3 pin header onto the coreboard. You will need to invert the header as you can only solder it from the top of the pcb as the 34pin floppy connector prevents access to the solder side of the pcb.

Remove the plastic spacer from the three pin header. I applied gentle pressure with a pair of needle nose pliers and it just slid off.

The next two pictures were mockups to show what we were doing with the various headers so they aren’t construction pics, rather just showing where things go.

Single row ( 20 pin ) r/a header mounted ( tip, make sure you solder all of the pins, not just a couple to hold it in place while you take pictures. I spent some time trying to work out what was wrong after i forgot to solder all of the pins )

Three pin header fitted to pins 36, 38 & 40 next to existing 34 pin floppy connector. 

This is where I soldered the right angle header, you can just make out the three pins from the straight header at the bottom right of the other header.

fit another piece of 5 way stright header to a piece of 8 hole by 2 hole vero board as shown below. I found the right angle socket made a good holder to prevent finger burn 😉

Note the piece of vero board needs to clear the plastic holder of the right angle header so a test fit is required before soldering things together

this is where the small piece of vero board needs to fit ( this pic still has the plastic header on the straight header which is actually removed prior to this stage. )

This pic shows the header/connectors all together. I used the right angle socket as an alignment guide to hold things in the right place as i soldered the vero board to the 3 straight header pins. Note care need to be taken that you don’t apply to much heat and cause the solder to holding the stright header pins to the pcb to melt.

An overhead shot of the right angle header and 5 pin extension that has been made from the veroboard addon thingy.

Mount another piece of veroboard onto the right angle socket as shown below. You need to take care that there is enough clearance between the veroboard and the floppy controller chip so it is possible to unplug the veroboard. I trimmed the left hand side of the veroboard to only have three rows with no pins. I then used some tinned copper wire soldered onto the unused rows to clamp the ide cable. I think this till change to use some sort of proper cable clamp before I finalise this.

This next part is a bit fiddly. I used some wire wrap wire ( just because I had some ) to connect the three straight pin header to the 5 pin extension header on the veroboard. Once again a bit fiddly as to much heat will unsolder the pins from the coreboard pcb. if you look carefully you’ll see the deliberate wiring mistake where I crossed two wires over. Numbering the pins on the vero board from left to right ( looking as per the pic below ) pin 1 -> pin 4, pin 2 -> pin 5, pin 3 -> pin 6, gnd ( all of the odd numbered floppy connector pins are gnd ) -> pin7 and ( not shown in pic ) +5v ( i used pin 14 of ic27 ) -> pin 8.

I’ve described this wiring only relative to the small piece of veroboard. The wiring table described later has a pin numbering scheme relative to the 25 way socket/plug combination that you’ve just built.

It boots 🙂

Wiring information. The simple CF pinouts are from left to right looking from the rear of the bee. Pin 1 of the simple CF interface aligns with Pin1 of the 128k coreboard X2 connector ( see mbee-8342-4-01 cct diagram ). The IDE pins as standard IDE. There are several gnd pins on the IDE connector, the ones chosen aren’t critical, just evenly spaced accross the connector.

Simple CF PIN Microbee coreboard Pin IDE pin Description
1 1 17 D0
2 3 15 D1
3 5 13 D2
4 7 11 D3
5 9 9 D4
6 11 7 D5
7 13 5 D6
8 15 3 D7
9 17 35 A0
10 19 33 A1
11 21 36 A2
12 23 Nc /port40
13 25 23 /xwr
14 27 25 /rd
15 29 Nc Clk
16 31 Nc /m1
17 33 Nc /iorq
18 35 Nc /halt
19 37 Nc Fside
20 39 1 /jlatch
21 36 Nc /int
22 38 37 (ide-cs0) /port60
23 40 Nc Ieo1
24 Gnd 2,22,40 Gnd
25 +5v 38 (ide-/cs1) +5v

I use a standard floppy power connector to provide +5 and gnd to the CF-IDE adaptor. I picked up +5 and GND from IC52, rear most 5v reg on coreboard. The other reg on the coreboard provides power for the dram.

There is very little height above the coreboard at the rear of the case. I’m waiting for one of the CF-IDE adaptors ( pic below ) and hopefully it will fit once the bracket is removed.

The Software and boot roms are slightly tweaked versions of Kalvis Duckmanton’s CF/IDE bios ub512hdbios_0_53 

Big thanks you the Kalvis, the BeeBoard and Stewart for their work, systems and advise.

 I’m in the process of uploading my mods back into the CVS system Kalvis has so we can keep the system software in a managed system.

I’ll post up again once I’ve done this with any relevant notes/instructions for the software.

I’m also waiting on a couple of other CF cards. So far this has worked ok with a sandisk 32M CF card. A no name 1G card doesn’t appear to work nor does an 8M canon CF card.

update #2 compact flash addon, deathly quiet but no smoke this time

Well,having sorted out the smoke 🙂 I managed to convince one of my original floppy drives to become a ‘was’ floppy drive. it is no more, it’s deceased.

Where the smoke came from. It must have been under some pressure because there was a lot of smoke!

Having recently had a big clean up, throwing out several 3.5″ drives in the process, I eventually unearthed a couple. One of which worked a treat. Just had to refit a connector on the floppy cable to allow for the 34 pin on the drive being upside down and sideways to the previous drive <sigh>. It’s a one third height drive so it’s rattling a bit in the case ( old drive was a half height ). But all is now good again.

My 8 (new) 41256 dram chips arrived so I added them to the core board as per the 512k upgrade instructions by Peter Broughton. I did get caught out a little bit as the floppy drive died in the middle of all of this, my ancient eyes and shaking hand produced a dry joint ( solder ) and the PAL on the coreboard was from a CIAB which didn’t support dual dram banks. I had made a variation on the 512k upgrade way back in the ’80s that compnesated for this but only for a single dram bank up to 256k. So luckily the other coreboard I had was complete with the required PAL.

I’ve also completed the 6.7 MHz speed mod.

I decided to try and use the PJB system along with the IDE/CF bootroms and bios code modified by Kalvis Dukmanton as a base. So I’ve now switched from my original code, bios and boot roms to this.

The bootrom is ok as is for the moment but it, along with the bios, will need a little tweak as my CF mod uses the 8 bit data xfer mode rather than the traditional 16 data mode.

I’m just working through the h/w interface ( physical side of things ) for a CF ( only ) ide adaptor and a few of the s/w things.

Keeping with the simple and cheap as possible theme, i’m using a ide to cf adaptor from ebay, some standard 40 pin ide cable from a PC, some vero board and some single row header.
It should all fit onto a 128k coreboard ( 8342 ).

Bare board where the header will be fitted.

Right angle header, left hand end will have small piece of vero board with extra pins to pick up pins 36, 38 & 40, gnd and maybe +5v that are on the other row next to the 34 pin connector.

Right angle socket under vero board, just visible at left. vero board needs to be this short so that it clears the FDC to allow it to be unplugged. Also need to keep the height down so it clears the top of the case

Where i think ‘ll mount the CF-ide adaptor or ontop of the next connector space to the right, closer to the DIN connector. Give or tack a smidgeon, the CF bracket mounting holes are the same spacing as the x3/x4 15 way sockets for the SCC serial ports. So it should be possible to mount the CF holder on a couple of spacers and have it accessable from the rear of the case.

Not shown are the cabling between the cf-ide adaptor and the vero board. Nor the power cable for the CF. most likely i’ll use a standard floppy power connector and plug into the cf-ide adaptor direct or I’ll add another small regulator.