Arduino Nut

Sorted by Squirrels.

Wednesday, 8 April 2020


I was asked if I made a cart that would enable development on the M5. I didn't but then some time passed and I did.

It's a fairly simple re-work of the Multi-II cart with data and some control lines broken out. And it's red. I've been paste-curious for a while now and I finally caved and ordered a stencil along with the PCBs. I've had a stencil before from the OSH people, hence the board retainers, but it didn't work out for me. This is from JLC and I have to say I'm very impressed with it. I've loved JLC for a long time now and despite trying other houses I keep going back.

I don't have an oven but I do have a very basic hot air rework station. Even at this introductory level  the process is simple and quick. I use a low temperature paste from the bay of E. The board can be pasted up, populated and cooked to perfection with a few waves of the hot-air-wand in a smattering of minutes.

But does it work?

Oh yes.

Here it is connected to an SD-X. A useful little board if I do say so myself. I should build some more really. It's very crudely integrated at the moment but the plan is to refine the interface.

This is the very first time my game BiggOil downloaded to the M5 using the board.

Right now the M5DEV decodes I/O requests into a simple read strobe and the SD-X listens out for it. When it sees the read request it puts a byte on the data bus. Repeat 8192 times. The SD-X is easily fast enough to service the IO requests and the result is an 8KB ROM image loading in under a second. 600mS to be exact-ish. It can go faster, I'm being a little conservative right now.

The plan is to either make a dedicated board to interface with M5DEV or keep it SD-X based. The former idea could be cheaper but more work, and the latter would give more options. I intend to add WiFi via serial using an ESP series chip. This could provide a basic user interface. The work cycle would be compile, boot the m5 into a helper ROM, upload code to sd-x, download code to m5. A round-trip of a few tens of seconds I reckon.

Oh yes and the M5DEV is also a fully-functioning first-class M5Multi-II!

Friday, 24 May 2019

Just in case...

Lots of cart owners have asked about shells. Up 'till this point there haven't really been any other options other than cannibalising an existing M5 game cart. This isn't really an option due to the rarity of these beasties. This is why I didn't really cater for casing a cart in the first iterations of the board design, opting for something pleasing to the eye.

Now I have a 3D printer that is all changing. Another M5 fan has published a design for a shell that holds a 'standard' PCB and I have used this as the basis for my own modification

The first attempt is promising. I have re-designed the cart PCB to include some detents that will, with an appropriately designed shell, hold it securely in place.

With a slight alteration to the case stand-offs the previous (pre-May 2019) PCBs can be held, and secured with a tiny blob of hot glue.

I will probably make these shells for those who want one but aren't able to print their own. I will also be publishing the .STL files as a remix of the original design - see the link at the top of the post.

For more information use the contact form at the foot of the page!

Saturday, 22 September 2018

Make your own M5 pad from scratch

Here's how the M5 pad is wired. Eagle files linked below.

Here's a zip with the eagle files in.

Ma5ter pad conversion

So that's what a master system pad looks like inside. For what I'll be doing with it today it's absolutely perfect. I'll be re-wiring this for use with a Sord M5.

The M5 joypad circuit needs a distinct common connection for directions and buttons. Having the separate button and pad PCBs is a gift.

So desoldering ensues.

There still needs to be some track cutting, the buttons should have no common connection. I'll need to interrupt the common and re-route it to one of the solder pads stage left.

Scratch 'n' Snipp. I've noticed at this point that the bottom left pads are conjoined. I'll have to see to that.

OK. Pads separated, jumper wire in place and the required diodes fitted. Ready for wiring now, we are ... almost. The fire buttons are connected to UP and RIGHT connections. The pads work by having 2 wires as selectors. By asserting one after the other either the pad or the buttons can be checked. The diodes prevent the buttons from interfering when it's time to read the pad.

OK. NOW it's time for wiring.


Now there was some devilish detail that I somewhat conveniently glossed over in the previous interstitial texts. Like the fact that the copper-exposing-scratching for the jumper wire was done in a very particular place. The surround of the little rubber contacts was carefully avoided. Did you wonder why the line was drawn on the PCB earlier? You did? Give yourself 5 extra points for observation. Very good.

The button PCB sits on a little rectangular plinth inside the case, so the additional wire needed to be placed so it doesn't foul.

With all that done the replacement cable is soldered.

The pad case has an internal cable restraint, very nice. Just make sure enough outer sleeve is cut from the cable so that the serpentine capture of the cable can sit snugly in the allotted cavity.

Very nice.

Wednesday, 11 July 2018

SD-X on MSX. Introducing MSdX!

All-in-One, Plug-n-Play

No bells, whistles, frills or frippery. MSX-1 all the way.

So far it provides an emulated drive A. Standard .dsk files are mounted using a DOS COM file or BASIC extension. Plans are afoot to hack in order to allow transparent access to the filesystem on the micro sd card.


Tuesday, 7 March 2017

Introducing SD-X

It was always my plan - SD for everything. And today we're one step closer. With a single interface board for ... well, everything. All you need to get sd-card powered fun from your favourite Z80 based 8-bitter is an inexpensive adapter board. And suitable code to access the card, naturally.

This is the first production board - ready for one lucky Tatung Einstein owner. We're still a way off full production but with this unit we're one step closer.

Currently X = Tatung Einstein + Tandy TRS80 Model 1. Next up..?

Tuesday, 28 February 2017

M5-Multi-II production pictures

Better late than never - unless you're talking about rescue from a perilous life threatening situation I suppose. Here are a couple of pictures from the first production run, alas nearly all sold out - which is the late bit.

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