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Member postings for IanT

Here is a list of all the postings IanT has made in our forums. Click on a thread name to jump to the thread.

Thread: Retro Computing (on Steroids)
18/12/2020 16:53:57
Posted by Roger Hart on 17/12/2020 12:17:35:

Anyone know how the CMM2 produces VGA. Is it some kind of fast loop does it use dma? Just curious, not really sure if I want to spend too much time on a VGA gadget, but I have a vga screen that has been kicking round the shop for too long.

Hi Roger,

The VGA graphics are generated by the underlying hardware but much of the 'programable' functionality is built into the BASIC engine. The CMM2 is built around a single 'Waveshare' MCU chip, which uses a Cortex-M7 32-bit RISC CPU core, running at 480Mhz and producing 1027 DMIPS. The MCU also has a double-precision FPU and Chrom-ART graphic accelerator. So just about every 'hard' feature of the CMM2 is on the MCU chip with just a few external components to enable connections to the real world.

Waveshare - Core 743i

MM Basic is closely coupled to this hardware platform, meaning that it has direct access to the 'metal' and whilst firmware upgrades have been happening pretty regularly, the MCU provides a well defined (e.g. fixed) hardware reference to base these upgrades upon. The VGA graphics are a good example, with a combination of very fast hardware combined with firmware designed to get the best out of it.

In many ways I think that's why the "Retro" guys like the CMM2 so much - it's like the 80's consoles (such as C64, Atari and Amiga etc) which were specific (e.g. stable) hardware platforms that could be explored and further 'tweeked'. There are disadvantages to devices like the RPi where both the OS and underlying hardware are constantly evolving - for some, they also present a constantly moving target...

Not really my thing but the retro-gamers are re-coding old 80's games (in Basic) and getting 30 frames per minute performance (it was originally half that). They've also recently introduced 3D graphics commands into the CMM2's Basic which are based on advanced MATH functions that I (frankly) don't understand but which apparently have all sorts of other useful applications.

The key thing is that MMB is implemented to get the best from it's platform - be that a tiny 28 pin MicroMite or the CMM2. There's nothing in-between to suck performance away. Many might see that as a major disadvantage but clearly some do not - and that is who this little box of tricks is for.

With regards VGA/HDMI - there are a lot of adapters around ranging from a fiver upwards. CMM2 owners seem to like the GANA boxes which are a bit more (about £12 on Amazon). I've got several older VGA monitors that still work very well and in fact I use an HDMI to VGA converter to connect my Pi 3B to one.



Edited By IanT on 18/12/2020 16:56:35

15/12/2020 21:26:15
Posted by Frances IoM on 15/12/2020 18:16:56:
dave think about palindromes of octal number the set is 0,1,2,3,4,5,6,7 to add 4 to 2 move the index from 2(assuming set starts from index 0) then move 4 positions, adding 6 to 2 will wrap around in set thus triggering a carry
thus the structures needed are (n,array of digits[index set 0..n-1) - adding 2 of these structures needs n to be equal (if not a copy into a larger array is needed) - the carry array is always on size n+1 and may have 1 in several positions this if carry set not all zero first extend the addition to size n+1 + add carry and repeat whilst carry set not all 0.

surprise 'Octal' Frances? I used to know that a long time ago - but all I can remember now is '7402' (Halt instruction on a PDP8)


15/12/2020 14:53:34
Posted by Michael Gilligan on 15/12/2020 13:36:03:

Almost incredibly:

I have just stumbled across my paper copy of FORTHWRITE issue 55, datedAugust 1990

This was published by FIGUK ... the FORTH Interest Group(UK)

No idea if they ever made it to the Internet.


I don't know about 'Forthwrite' Michael - but the US version (Forth Dimensions) certainly was archived. I haven't managed to find the site I originally downloaded my copies from (it was some time ago now) which was sorted by volume. There are some FD editions available at the site below - although they seem somewhat randomly ordered.

Forth Dimensions



15/12/2020 13:03:35

'Starting Forth' by Leo Brodie - the classic intro book for learning Forth. Can be found here as a PDF or online version. The illustrations really help to understand stack manipulation in an amusing way.

Starting Forth - Leo Brodie



15/12/2020 11:54:32

SoD - having said I wasn't a Computer Science bod - you went ahead and set what I suspect would be an exercise for first year Computer Science Grads - who presumably have been introduced to "SoDs Algorithm" or some such as part of their course !

Your problem is clearly not a simple as it might first appear but by 'Trial and Error' I did manage to get a "Bucket" approach working (no bounds checking or anything) but clearly this wouldn't scale for the problem you described. This programme took me about 30-40 minutes (the next day) over coffee and whilst it might not impress a programmer - I was quite pleased getting this far from scratch. A T&E approach is very simple (and fast) to do with MMB - so it suits a programming 'dummy' (like myself) who is trying to work things out as they go along.

' Numeric Palidrome 091220/1
DIM N%, L1%, M1%, H1%
INPUT "Input seed number"; N%
L1% = N% MOD 10
M1% = ((N% MOD 100) - L1%)/10
H1% = ((N% - L1% - (M1%*10)) MOD 1000)/100
PRINT L1%, M1%, H1%

I now have newer programmes that use more iterative processes and that I will (eventually) get to work - but it's very much my Christmas Crossword Puzzle - so I have a go at it when I have a quite moment and feel in the mood (which as Christmas gets nearer is harder to do).



PS Should have illustrated Forth with classic example code (for a washing machine) " Rinse Wash Drain Dry "

Edited By IanT on 15/12/2020 11:58:32

15/12/2020 11:25:36

We seem to have a lot of common background SoD laugh

All this talk of Nascom, Zeap and now Forth. It took me forever to type Fig-Forth into my Nascom system and to then find all my typos and get it working - but it was really the only way to get my graphics card (based on a TI chip) running in a usable way.

I've managed not to mention Forth here (thus far) but for control/embedded uses, I would suggest that folk look at MeCrisp & MeCrisp-Stellaris by Matthias Koch. I have it running on STM "Blue Pill" boards which may have been replaced by newer products these days but could be had for about £3 - very reasonable for a complete RTR STM32 board.

MeCrisp Forth

Forth is a threaded (stack-based) language and RPN is one of the side effects of using a stack to perform everything. I think the simplest (& maybe best way) to describe Forth - is that it is extremely useful to write other 'application-specific' languages with. So if you need a robot-control language, a plain-language to G-code parser, a telescope user interface - Forth will let you write a programme that uses application appropriate wording/commands - e.g. "Left Arm 22 mm Up" or " Traverse Head To Home" or "Track X Y Z Co-Ord From Set Time" where each 'word' (Left, Arm, Head, Set) can be thought of as a sub-routine that is executed.

I won't bother to further explain it here (like BASIC most programmers seem to hate Forth btw!) but if you would like to know more about MeCrisp (Forth) then have a browse here...

MeCrisp (unofficial) Doumentation



Thread: Parting-off Tools for Small Lathe
14/12/2020 11:50:00
Posted by James Alford on 14/12/2020 07:59:42:

What type of parting-off tool do people recommend for use on a small lathe: I have a Flexispeed? I have a one of those holders which take a flat blade from RDG, but the fixing for the blade is not very good. It tips the blade over at angle and does not grip the blade very well, allowing it to slide in the holder, rather than cutting the metal.

I have tried grinding my own from HSS, but not with any real success.



Hi James,

You seem to have already identified several problems with your parting tool holder/blade - so you need to fix these before you go any further. If the blade is not vertical it will most likely foul. If it is not firmly held, then it will not cut correctly. This seems to me to be a straightforward mechanical problem.

So do you have the correct blade for the holder (silly question perhaps - but is it in upside down?) and/or can you slightly modify the clamp to grip the tool better? If you cannot fix these problems, then either try fitting a new blade (perhaps check with RDG what the right blade is first) or get a new holder. Once you have sorted the obvious problems, then we can talk about how best to use it.



Thread: Sentinel DG8 Steam Lorry Drawings
13/12/2020 21:30:28

Adam, a few years back I needed an accurate source of drawings for a Sentinel 100HP 4wVBT.

We (the G3 Society) wanted to build an affordable 'entry level' scale model of it. Eventually, we contacted the Sentinel Drivers Club and they kindly provided (photos of) the original GAs, sufficient that I was able to produce good CAD files from them.

I'd suggest that you contact the Club and ask if they can help you too?

Sentinel Drivers Club



g3 agm 2015 031.jpg

Thread: co-axial indicators
11/12/2020 22:41:11

One of these has been on my TUIT list for a very long time....not sure it's ever going to make it though...




Thread: Lidl Portable Bandsaw
10/12/2020 23:58:05
Posted by Martin of Wick on 10/12/2020 21:40:25:

This brand of tool (Milwaukee clone) was originally designed for freehand use. The addition of the stand and vice was clearly an add on afterthought to extend the utility of the device- compromised by poor saw geometry and poorly designed mount location.

Yes, good point Martin - that's the reason, same as a chain saw now I think about it.


10/12/2020 21:23:53
Posted by KEITH BEAUMONT on 10/12/2020 20:41:04:

I also found it curious that the cutting forces are loading the movable jaw and not the front fixed one. Do all metal bandsaws run this way.? When purchasing alternative blades,the direction of the teeth is not specified, so I assume they all do.



Well on my INCA (wood) bandsaw I initially thought the replacement blades I'd purchased were "wrong-hand" Keith - however the light finally dawned and gripping the blade in both hands - I turned it inside out - and now the teeth point in the right (or is it left?) direction   



PS So it's the direction the motor turns in that's important...


Edited By IanT on 10/12/2020 21:25:46

10/12/2020 19:34:49
Posted by MC Black on 10/12/2020 16:59:20:

On a previous visit to this thread, somebody mentioned reversing the jaws of the clamp - so that the jaws were nearer the cutting blade.

I've re-read the whole thread (twice) and cannot find that posting.

This is probably because I'm old and senile - but can anybody point me at that posting, please?


Probably Clive's comments about there being too much overhang between the vice and the blade MC.

You cannot "just" reverse the vice - it won't fit. I extended my clamping 'plates' over to the blade side (see first page) such that there was very little gap between them and the cutting blade - and the support is much improved. However, the blade doesn't pull the work into the fixed jaw but away from it - so it runs the wrong way to my mind. However, you cannot (simply) turn the vice around. Maybe that's what you were thinking of.



Edited By IanT on 10/12/2020 19:35:43

Thread: HELP in constructing 5 inch gauge points
08/12/2020 21:20:20
Posted by Brian H on 08/12/2020 15:20:33:

I would have thought that the garden railway people should have an answer.


Well, I do have a method for G3 turnouts but perhaps the EIM article will be more appropriate for David's needs.

Anyway - I use paper templates generated by a programme called Templot2 - that I purchased many years ago. I will admit I never got to grips with using it to design the whole track - but selecting turnout types and radii is a very simple job and can be used to generate overlapping PDFs for print-out. Once you've got a template to work to - it's pretty straight forward to lay sleepers and rail on top.



Thread: Retro Computing (on Steroids)
08/12/2020 16:45:47

As usual it's about context Dave. Everyone who visits this Forum is different - they have different skills, interests, available time and funds.

In the past year or two, I've dived into 3D Printing, learned a little Open SCAD, spent time working on Solid Edge 3D CAD, finished a few workshop projects and (even) progressed some of my Gauge '3' locos (and finally built a rolling road too). I have an old house (in a large garden) that also needs a lot of my attention. So my "context" is that I'm of an age where I've started to think a lot more carefully about what new things I begin and even if I can keep up with everything I've already started.

It would be nice to have the time to explore new tech and I have been tempted. If my Grandson continues with his interest in 'Robots', then I might dive into Python and ROS and help him (although the 'Black Boxes' he'd be talking to will have a 'Mite' inside them). But clearly something else would have to give.

I have tried other 'tech' and discovered that within my 'context' - e.g. an ageing brain, no professional 'coding' background and many other demands on my time - the Micromite has been a very good solution for my particular needs.

As Kiwi commented "It makes the physical and intellectual interfaces easier than anything else I've come across." In other words, you don't need to be a Computer Scientist to use them and that's the key thing for me.



Thread: Pennsylvania A3 Switcher
08/12/2020 15:00:50

Lovely work JAS - Congratulations!

Phil - Kozo designs don't use any castings at all - everything is machined from the solid or fabricated - including the wheels. He even describes how to make a pressure gauge if you are so inclined....

Unlike the Pennsy, most of his designs are for N/G logging engines (by Shay, Climax & Heisler). For these, he describes how to modify commercial gears but does also show how to machine your own skew gears if you want a more prototypical gearing arrangement on your engine.

As John says his books really are in a class of their own - with everything there - (fold out) dimensioned drawings, isometric illustrations, inventory lists and very detailed step-by-step build instructions.




Edited By IanT on 08/12/2020 15:06:32

08/12/2020 11:06:48

Kozo's books are a wonderful blend of Engineering and Art Mark - I have all of them.

Whilst in practice I will never actually build any of his engines, I have learned a great deal from studying his methods. I'm sure you will find working through his very clear instructions enjoyable and rewarding. I like your tools and your "attitude" (in making them first) is very 'Kozo' - I'm sure he would approve.



PS For anyone interested in Kozo's books - second-hand versions often appear at silly prices but the books are still in print.

Kozo A3 Pennsy


Thread: Retro Computing (on Steroids)
07/12/2020 21:33:34

For anyone who would like to 'sample' MicroMite Basic (MMB) there is a version for PCs (I run it on my Win 10 laptop). It doesn't have many of the features that other versions of MMB have, such as all the communication, display and external I/O options - but it does support Serial Comms and the PC's disk filing system. So I can read and save .cvs files for instance (usable by Excel) and also open COM ports.

" This interpreter runs in a DOS box under the Windows operating system and will work with Windows versions from Windows XT through to Windows 10. It does not need installation, you just copy the executable to a convenient location on your computer and run it from there. "

MMB for PCs

If you find MMB isn't for you, you can just delete the .exe file and it will be gone - it's that simple. It won't change anything on your PC.

Here's a Change Wheel programme (that I spotted in MEW 277) you can use to try MMB with. Just Cut & Paste it into a Notepad-type document (not Word! - I use Notepad++) and save it with a .bas file extension. You can then load it into MMB.

' Change Wheel Calculation
' by Mike Aireton - from MEW 277 Feb 2019
Input "Input required TPI ", W
Input "Input deviation ", Z
X = W + Z
Y = W - Z
For A = 20 To 75 Step 5
For B = 20 To 75 Step 5
For C = 20 To 75 Step 5
For D = 20 To 75 Step 5
If A = B Then GoTo SKIP
If A = C Then GoTo SKIP
If A = D Then GoTo SKIP
If B = C Then GoTo SKIP
If B = D Then GoTo SKIP
If C = D Then GoTo SKIP
' Assumes 8 TPI Leadscrew
If A*B*8/C/D < X And A*B*8/C/D > Y Then Print C;" "; D; " "; B;" ";A*B*8/C/D
Next D
Next C
Next B
Next A
Print "DONE!"

Mike said it ran on his PC/Basic in about 15 seconds - but it runs on mine in 2-3 seconds. Fast enough.



07/12/2020 12:52:52
Posted by Bazyle on 07/12/2020 12:07:03:

Yep, UK101, cheaper than a Nascom 2. I had a wordprocessor on it that was just 2k bytes. What does Word need nowadays?

Happy days awaiting awaiting the latest edition of Practical Computing (and if I was feeling a bit flush 'Byte' )

The UK101 was very similar to the Ohio Scientific, both being 6502 based but I finally (after much agonising) decided a proper 'bus' was a good very idea and selected the Nascom 2 (Z80 based) . I think it was about £300 with the PSU and came as a large PCB and a bag of components. Several days (and many dry-joints) later, my wife couldn't understand why I was so happy with the red LED flashing on and off.

Wife " What's it doing?" - Me "It's flashing the light on and off every second "

Wife " Yes - but what's it doing?" - Me "I've programmed it to turn that light on and off every second "

Wife "Is that all it does? " [short pause] " And what did you say it cost? "




06/12/2020 13:30:12

I think many here may remember their first steps in "Home Computing" back in the late 70's and early 80's.

An inexpensive SBC (single board computer) that booted immediately into interpreted BASIC could (with much laborious typing-in) deliver what at the time, seemed to be quite good games graphics. But if you needed real speed - then an assembler was always required.

In 2011 Geoff Graham introduced his first monochrome 'Maximite' SBC, which was based on the PIC32 chip. This was quickly followed by the 'Colour' Maximite and then many versions of the MicroMite (for embedded control) - ranging from simple 28 pin DIL versions, scaling up to very fast Neucleo STM boards. All of these use a version of MicroMite BASIC (MMB) matched to the available hardware features but sharing a common language base .

Earlier this year, the latest Colour MaxiMite (CMM2) was launched and attracted a great deal of interest. Some very gifted people have helped to develop and test the CMM2, which is ARM Cortex based. Since then, MMB for the CMM2 has been rapidly improved. Most recently a 3D 'engine' has been included into the MMB interpreter. To be clear, no external libraries are required - this is now a built-in feature of CMM2 BASIC.

I know very little about graphics programming but I think the results are pretty remarkable. The following demos are both written in (interpreted) MM BASIC.

CMM2 - 16-bit colour, 1335 vertices, 2452 faces

(the full programme is listed by Peter Mather in his comments below the video.

CMM2 - Rotating Ball with Ambient Lighting

All of this is (of course) way beyond my programming abilities and I haven't purchased a CMM2 myself (although I've been tempted). I'm just using my 'Mites' for embedded control purposes. But I'm really impressed with how quickly this latest 'Maximite' SBC has been developed by just a few (very talented) enthusiasts.



Thread: Lidl Portable Bandsaw
06/12/2020 09:54:30
Posted by Ady1 on 06/12/2020 08:46:32:

A chap here has a simple system for helping the blade cut properly

I will probably try using a bungee cord

Some interesting points Ady and worth trying I think.

I guess he's a bachelor too. I showed my wife this video and she has revised her view of my 'inside' workshop - It seems I'm much tidier than she had always imagined! wink



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