Page 1 of 1

Slow firmware for 8" drive

Posted: Wed Feb 07, 2018 5:53 pm
by thunter0512

this is my first post on this forum. Thanks for this cool tool.

I have successfully imaged an 8" floppy disk using a Mitsubishi M2896-63-02U drive connected via the FDADAP board to the KryoFlux board. My only problem is that the stepper motor is driven too agressively by the firmware. It sounds like the step rate is too high or the step pulses are too short or both. It sounds terrible while calibrating or positioning back to track zero but even for single steps while reading. When stepping the drive sound very different from when it is driven by ImageDisk via a standard PC floppy controller.

I am using the default firmware called "firmware_kf_usb_rosalie.bin" distributed as part of the official, NOT the firmware from the directory "firmware_fast".

About 8 years ago Mr Vince posted an article with the title "Please test: SLOW firmware":
Unfortunately the firmware link in this article is no longer available. As it is very old I suspect it wouldn't be compatible with the current DTC 2.51.

I don't want to destroy my 8" floppy drive by driving the stepper motor outside of its specification. Could I please have a slow version of the firmware or if possible the source to the firmware so that I can fine tune it for my drive (I am an embedded software engineer with 35+ years of experience and would be happy to help with this project).

I would like to suggest to add an optional set of parameters to DTC which are passed down to the firmware:
1) step frequency
2) step pulse length

This may be more elegant than having multiple firmware versions.

You may even want to consider ramping up/down the step frequency to reduce the stress on the stepper mechanism.

Thanks and best regards
Tom Hunter

Re: Slow firmware for 8" drive

Posted: Wed Feb 07, 2018 7:40 pm
by SomeGuy
Nice, that is the same model of drive I have, but I use a home-made passive adapter rather then the FDADAP since this drive model does not need TG43 support.

You can't damage a stepper motor by running it to fast or too slow. At worst it will miss a step and wind up on the wrong track. If you are writing, that can cause data loss, but no physical damage.

Are you sure the step rate is too high?

Most drives actually SOUND worse when using a lower step rate. With a lower step rate, the motor spends more time starting and stopping, which vibrates and reverberates things. Higher step rates are usually much quieter.

I'd have to check the manual, but I suspect this drive might actually be designed for higher step rates. However I'm not aware of any circumstances where a floppy drive step rate can be too slow.

It is a little odd that step rate is not software selectable in the Kryoflux, but since it not meant for random access and defaults to a lower step rate, that should rarely be an issue. (although the drive in that thread apparently needed a REALLY low step rate)

I believe ImageDisk normally selects a much higher step rate. ImageDisk has a command line option SR=1-16 that lets you change the step rate. (Although some BIOSes might override that) You might experiment with that to see how different step rates sound.

Re: Slow firmware for 8" drive

Posted: Thu Feb 08, 2018 4:34 pm
by thunter0512
Thanks SomeGuy,

I got FDADAP because for the price it was just not worth building my own and I was waiting for the KryoFlux board anyway. Plus it had the TG43 support which is useful for my "dumb" CDC drives.

Today I tried again but this time I calibrated using the KryoFlux GUI rather than the DTC command line. Strangely this time the stepper behaved and sounded as expected. Supposedly the GUI is just a wrapper around DTC.

I keep going and image some more disks. If the problem shows up again I will report back in this forum.

Thanks and best regards
Tom Hunter

Re: Slow firmware for 8" drive

Posted: Sat Feb 10, 2018 6:20 pm
by IFW
Just like SomeGuy said, the lower the step rate, the worse the drive sounds while stepping... so it's actually very misleading!
If you can barely hear anything at all or a slightly highly pitched tone, then the head is stepping at a fairly fast rate.
Due to many (5.25'' and 8'' and only some 3.5'') drives not working reliably at a faster step rate the KryoFlux host software package uses the "slow firmware" as default (for quite a while by now), but the "fast version" is still available in the "firmware_fast" directory of the distribution package.

As for user settings for drives: thanks, I put it on the TODO list.