Drobe Launchpad | Fit a USB combo-media drive to your RiscPC

Fit a USB combo-media drive to your RiscPC

Published on 13th Jun 2004, 23:00:09, source is drobe.co.uk
By Ian Jeffray

Hardware How-to

As RISC OS users delve further and further into the realms of digital cameras and other uses of compact storage media, Ian Jeffray shows us how he combined a combo-media drive and the STD UniPod. Disclaimer: This article assumes you're competent with electrical based practical work and any modifications carried out on your kit is done entirely at your own risk.

Driving further
I finally got my hands on STD's UniPod at the Wakefield show in May. UniPod provides a wealth of features on a single podule: USB, twin IDE, 10/100baseT ethernet are the primary functions. Interestingly, the USB function is provided on a four-pin header on the board, as well as two standard USB sockets on the rear of the podule.

This gave me an idea - attach an internally-mounted smartmedia to the podule, rather than continue with the external reader I had been using, just to be a bit tidier.

I've been using an insanely handy tiny 6-in-1 USB CM/MD/SM/MMC/MS reader by PQI, and had got this working with STD's 'MassFS' generic USB storage filing system with no particular fuss (Pop 0483:1307=LRTC in !MassFS.OtherDevs) so I had some confidence (whether justified or not) that getting another card reader working would be no big deal, so just picked one that looked nice. I chose the FA402M drive from Mitsumi for 15UKP from scan.co.uk. This drive is a combo floppy drive and multiple card reader in a device no bigger than a standard floppy drive - quite neat, and I was even able to pick the colour of the front bezel to match my machine's case.

The drive connects to the RiscPC via three cables; standard floppy power connector, floppy drive cable, and a USB cable for the reader.

The USB connector is keyed to match the header on a PC motherboard, but the key lug can easily be removed by a sharp knife..

..and it then connects straight to the USB connector on the UniPod..

USB connector on the internal Unipod header

..being careful to ensure the four pins match the four wires on the plug (there's an unused hole at one end) Power the machine up and, from the command line, *usbdevices shows that it's working correctly:
Device number 2 (36901c0c) on isp0 Device conforms to USB specification version 1.10 Vendor (0x55aa) : Product (0xb012) : 8-in-2 Device release : 2.00 Serial number : BB8230BB57

MassFS then needs to be told about the device; take the vendor and product codes from the *usbdevices output and pop them in the "OtherDevs" file inside MassFS. You've got to derive or guess the capabilities of the device and what flags must be provided to MassFS to make it work well with that device. A bit of fiddling around and a few reboots and it seems that the FA402M drive works well with the following settings in the "OtherDevs" file: 55aa:b012=LRTCQ All then works nicely and I was able to read the pictures for this article directly from the SmartMedia card in the drive:

Next, getting the floppy drive working. That's a bit more fun. RiscPCs use specially modified floppy drives, as the floppy drive connector is not fully PC standard. Fortunately, this is easy to work around. RiscPCs expect the floppy drive to be configured as Drive 'A'. PC floppy drive are, for various good reasons, set as Drive 'B' and these days can't even be changed to be Drive A. More annoyingly than that, the configuration of the RiscPC drive connector activates the "Motor B" and "Select Drive A" lines to run the drive which is just, well, odd. To fix this, we can simply modify the floppy drive cable, rather than messing with the drive.

You can modify the standard RiscPC floppy cable or, as I did, destroy a PC floppy drive cable, giving the option of going back to a standard RiscPC floppy drive later.

First, slice off the twisted part of the cable - this is NOT the twist we want as it's only for changing full drive B's to A's.

Throw away the bit with the twist. Unhook one end of the cable and separate conductors 10 through 12 (3 wires in all). Twist these wires around, and clamp the cable back together. Remember to count from the red edge of the wire as conductor 1.

This end of the cable connects to the motherboard, turning the RiscPC's interface into (almost) a standard "Drive B" PC interface. You can use this cable to connect a standard PC floppy drive, of course, not just the FA402M.

Now we can just replace the RiscPC's floppy with the new FA402M drive, and the job's done.

After thoughts
Remaining niggles with this project are that MassFS must be reloaded or manually run from !Boot for the drive icons to appear - the USB subsytem currently seems to be unable to cope with permanently
connected MassFS devices.

Please note that I've had no response from STD about this project, so you connect to the internal USB header at your own risk - I've had no official documentation regarding its use. Note also that the MassFS settings were derived by me by pure experimentation, and I give no guarantee that it won't corrupt your data or lock up the machine. (Although it's been fine reading and writing SmartMedia for me).

Links
STD UniPod website

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