SD Card

[epaell]

I've been playing with interfacing a micro SD card to the MECB 6809 system (based on the Corsham Tech SD interface https://www.corshamtech.com/product/sd-card-system/ - sadly the original designer passed away and so I've just been trying to find what I can to get it to work). I wanted to simplify the design by using modules that now exist for the Arduino (so it required some changes to the way it worked). I finally had my first boot of FLEX off an SD card:


As you can see, FLEX isn't Y2K compliant so I had to start with an old date to begin with (I believe there is a patch for this).

Unfortunately the interface is a bit of a dog's breakfast:


On the plus side, for the most part it is just wiring to existing modules (an Arduino, an Realtime clock module and an SD card module) and connecting it to the PIA port of the Motorola I/O card ... so while simple, there are just way too many potential cables to come loose (which is where most of my debugging time was spent - particularly as I don't have a dedicated location where I can keep this birds nest safe and each time I move it I seem to lose a connection somewhere).

Apart from the rather ugly wiring, it just required a few minor additions to the ASSIST09 ROM (to provide the interface routines) and writing a small loader routine/driver for FLEX. There is still one nagging issue in that the sectors/track is not passed correctly (I'm still trying to work out how that was done originally) - so at the moment I've hard-coded this just to test whether the hardware itself is working. Otherwise, I'm quite chuffed to have got it to this point.

[Editor]

I've been playing with interfacing a micro SD card to the MECB 6809 system ...

Awesome work! Thanks for sharing your journey. Love the interface. A rats-nest of wires is always a great sign of very active prototyping!

I've been busy with PCB design in my free time lately, but I'm also itching to get back to some coding and prototyping. So at this point, no real progress from me yet on my CF card interface plan.

[epaell]

I "think" I fixed the sector/track issue and am now directly able to boot off a FLEX disk (without any hacks in place) ... and can also boot from the ASSIST09 ROM without loading any additional code (which is a bit more convenient). It's still somewhat hacked as I need to run a particular address (just want to get it running first before taking any further steps).

[bugeyedcreepy]

I "think" I fixed the sector/track issue and am now directly able to boot off a FLEX disk (without any hacks in place) ... and can also boot from the ASSIST09 ROM without loading any additional code (which is a bit more convenient). It's still somewhat hacked as I need to run a particular address (just want to get it running first before taking any further steps).

That's Awesome!! Top job! I'll be following this as well...!

[bugeyedcreepy]

I've been playing with interfacing a micro SD card to the MECB 6809 system ...

I've been busy with PCB design in my free time lately, but I'm also itching to get back to some coding and prototyping. So at this point, no real progress from me yet on my CF card interface plan.

..... bugger.

If I could help out with anything, then by all means let me know - I'm just not sure what I could do - maybe some documentation of sorts to free up your prototyping time for you?

EDIT: or even if you can point me in the right direction on my own designs I discussed with you earlier, perhaps I can work on something to cut down on your own prototyping timeline?

[Editor]

If I could help out with anything, then by all means let me know - I'm just not sure what I could do - maybe some documentation of sorts to free up your prototyping time for you?

EDIT: or even if you can point me in the right direction on my own designs I discussed with you earlier, perhaps I can work on something to cut down on your own prototyping timeline?

As for my plans, a lot of them are still mostly in my head and on informal notes. The usual iterative design process! Which also means my design thoughts keep evolving over time. Unfortunately, I always plan to achieve much more in a day, than I actually get done. But I reassure myself, by reviewing what I did actually achieve each day! Also, when you get “in the Zone” on a project, time really just disappears!

As far as what you can do to help out? My best advice is to always just follow your own personal passion. Just dive into whatever you’re most interested in doing / achieving, and remind yourself that you can do anything!
Perseverance is the key to solving any challenge, and there are several of us here who (I’m sure), are happy to share their experience and try to answer questions along the way (if helpful).

One of my fav mottos is: Life is a learning experience. Try to learn something new every day!

[epaell]

Oh, I just saw your mention of NitrOS9 in another thread (https://github.com/n6il/nitros9) - I also notice that it supports the Corsham version of 6809 (which is basically what my SD card implementation was based on). Unfortunately I just pulled my prototype apart because the wiring was so unwieldy and constantly coming apart each time I tried to use it - otherwise I would've loved to have tried this. If I get to the stage of making a board this'll be the next thing I try.

[epaell]

I watched a 5 minute YouTube video on KiCAD and so learned everything there was to know about making PCBs with it - LOL - so I gave it a whirl to convert my birds nest interface into something that wasn't going to break apart each time I looked at it. It's not as finely crafted as Greg's boards and I mostly cheated and used the auto-routing feature because I didn't have much time to do this. In combination with an RS-232 terminal, I now finally have a stand-alone MECB 6809 system that can be used for writing, saving and running software under the FLEX operating system:



The disk images are held on a 32 GB SD card and there are FLEX utilities to list the disk images and mount them on the fly. It's also possible to eject and insert a different SD card if 32 GB isn't enough (the board automatically mounts the device) It also has a real-time clock which also appears to be working.

There is still something a bit odd with the board in that I can't seem to upload new firmware to it while the shield is attached (this used to be fine with the birds nest version) - so clearly I messed something up in my haste (and it is somewhat annoying because there is a lot of useful debug information that can come through the PC-interface that I can't access with this version). Something to look into when I get a chance.

Here is a not-so-great close-up of the entire system - it's still a bit of a birds nest ... but a slightly more manageable one:

[Editor]

I watched a 5 minute YouTube video on KiCAD and so learned everything there was to know about making PCBs with it - LOL - so I gave it a whirl to convert my birds nest interface into something that wasn't going to break apart each time I looked at it.

That's awesome work. Looks a lot tidier!

I suppose one day, a 3D printed case might be the way to go. I had earlier envisaged creating a nice cube style case for a MECB based system, basically for finishing off a completed system design (as opposed to the ever evolving experimentation system that MECB was primarily designed for).

I think I first had the 3D printed case thought when I was envisaging a CreatiVision re-creation, as one potential "finished" MECB based system. The 100mm square shape of a MECB system would make a tidy cube look, possibly reminisent of a minature NeXTcube. LOL

[epaell]

That's awesome work. Looks a lot tidier!

Thankfully it is all just mostly standard cables now i.e. lots of USB plugs for supplying power, RS-232 DB-9 for communication, PS/2 for keyboard and HDMI for video (on the terminal) and a simple ribbon cable connecting the parallel port to the micro-SD interface. So lots of cables but easy to connect (and less likely to unplug as I move it off the dining table for storage until my next bit of free time for experimenting with fun stuff.

as opposed to the ever evolving experimentation system

Indeed, that is part of my problem, I'm continuously mixing and matching cards - which makes a case a bit of a problem. I was considering something a bit simpler just to make moving everything a bit easier and perhaps just having a base onto which I can mount the main bits and pieces but still have access to the bus for unplugging/plugging. I'm just not well set up for building such things (and I don't have a 3D printer) - perhaps a simple perspex sheet would work ... or I could go old-school and do something out of plywood.