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Forum Index : Microcontroller and PC projects : What I/O boards do users want?
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donmck Guru  Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
My friend and business associate Richard (http://emx.net.au) will be working on I/O boards for the Maximite Computer. He is on this forum also. What we have to decide is what users want most in the way of I/O boards, and produce them. All comments welcome. Cheers Don... https://www.dontronics.com |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
Don, I currently use a number of small boards that "mostly" suit my needs. They have 8 TTL in, 8 TTL out, 3 analog in, 1 humidity in and 8 temperature in (DS18B20). The main reason I use this particular board is its *ethernet* connectivity. It also has around 4000 lines of programmable "logic" - not basic or C, but something like a hybrid of assembler, ladder and C. Its biggest failing (to me) is the inability for boards to communicate between each other in a co-operative control network, and no display (not even a 4x20 LCD). I'm working with the developer for that to overcome some of its limitations. The maximite (which I don't have yet) would appear to have a lot of those issues overcome already - but it doesn't have ethernet. In no particular order, I'd love to see: * support for 2x16/2x20/4x20 type "character displays" (I know, it has VGA, but for a dedicated controller the size/power of a VGA is unjustifiable) * Ethernet support (Would need to do DHCP client, some rudimentary sort of http support to allow a remote computer to read things and ideally write back to it) * Support at least 10-bit A/D input (ideally 12 or 14 bit) * Support DS18B20 sensors *in a bus* not just one-per-IO-pin Physical interface via smallish screw terminals always seems to be more convenient than the IDC headers many boards have. I'd like to see A/D inputs in the 0-5V range (or ideally, with a simple resistor change to make it 0-10 etc). A cheap amplifier to give 0-50 or 0-75mV would be a great option too (read current directly from shunts). I guess most of us are running low voltage outputs, but increasingly 240V AC rated (and isolated) would be great. Current could be quite low, say 1A. That should help keep the relay and connector costs and sizes down. I'd like to see at least 4 outputs like that. (Small SSR might be an option) Might even be practical to make a "universal" board that you (and/or the user) could populate with the bits they need, as they need them. Those the sort of suggestions you're looking for? Oh, yeah, and I'd like the fully populated, all-options included board to cost about $3.50 :) |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Hi Ross, Yes they are the sort of suggestions we are looking for, and the fully populated at $3.50, well is that USD or AUD you need it at? 
You pretty much covered the full spectrum of I/O, so I'll try and cover a bit of it. Cheap LCD will be a must, I think Geoff has mentioned this is the past, or has it covered, but it is trivial for this beast. Ethernet, again, I think if you have a look through the archives, Geoff has this on his to do list, but it will be a few months, as he is in Darwin, and doing a round Australia camping holiday, and will be returning to Perth in September. So it may be September before you see any big movement with the Maximite firmware. He is doing small updates on the road, and only has USB Modem comms from a notebook, so he can't always be on line. I have noted all your other comments and suggestions, and will make sure Richard reads through them, as he will be the one designing the I/O. BTW I have never seen a Maximite, so I haven't used one. Richard contacted me last Saturday, and asked me to re-read my Silicon Chip articles. So my involvement is a week old. I read through all SC articles when Leo printed them, but the penny didn't drop, that this is an $8 chip doing all of this work, and the way Geoff has knitted the project together, really puts the icing on the cake. He really is a happy little Maximiter! Cheers Don... https://www.dontronics.com |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
From a wind/solar control point of view, we need some sort of PWM output. In its current form the Maximite can not provide that, but I think Geoff is working on I2C data output. We could use I2C to talk to a PicAxe chips like a 08M, and it can do the PMW output for us. I2C will open up a whole range of goodies, like dallas clock chips, and the PicAxe range of chips. And maybe a I2C to ethernet controller. But for me, a PMW output board, with I2C communication. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
From a wind/solar control point of view, I would rather see an I/O board for your readers have a priority Glenn, as you have been good enough to sponsor the Maximite group. However, as you have suggested, Geoff should be able to come up with serial I/O routines later this year. Sure it could be bit banged, maybe even with Basic on a 32 bit PIC running at 80meg, but I feel the wise solution at this stage is to wait patiently for Geoff to do his thing, and we will have all the serial I/O we need. Cheers Don... https://www.dontronics.com |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah I can wait, I know Geoff will have a lot on his plate. Input wise we are well catered for, ( serial data been the exception ), I've been playing around the with frequency and period inputs, and the analogue inputs are very fast, I've had it taking over 1000 AD readings per second. I think the 12 or 14 bit AD resolution Ross mentioned above is allready built in. It is possible to make a slow PWM output in software, say at 100Hz, with the existing firmware. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
I would think so Glenn. The speed capabilities of MM-Basic would be the only restriction, and I am not familiar with what can be done just yet. In the TRS-80 days, when Basic got too slow, we called in line assembly language routines in the middle of Basic lines of code. You had to "POKE" the machine code into memory initially with Basic, but it did work. I don't know if Geoff has provided for, or looked at ML calls to date. I always remember Basic bogging down at times, it would tie itself in a loop. To do a quick test for this, we would put an off tuned radio (noise only) near the motherboard, and you could tell when Basic bogged down into crazy loops while it cleaned up arrays and memory behind itself. This is when you needed to leave Basic, and get a driver going with Assembly code. But then we had an 8 bit Z80A micro running at 1.79Mhz with 4 to 12K Rom, and 4 to 16K ram. Cheers Don... https://www.dontronics.com |
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| rhamer Senior Member  Joined: 06/06/2011 Location: AustraliaPosts: 174 |
Hi Chaps, Just in case you were not aware I have already produced an expansion board for the Maximite, that solves the problem of interfacing into the IDC connector. It also has the RS232 level shifting hardware for the much anticipated Serial Comms when it arrives. My view on such external add on boards is that where possible only implement the hardware, and leave the software to the Maximite. Creating a separate board with it's own micro narrows the flexibility of the overall package. I agree that having such protocols I2C is a good idea. Regards Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
Couldn't agree more Rohan. Using a Picaxe to produce PWM for the features that Glenn was talking about, is one way of going about it short term, but long term, it is all about getting the max out of the Maximite. Cheers Don... https://www.dontronics.com |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
The other thing that I think is important is not to loose sight of what the Maximite was designed to be. There are already hundreds of single board microcontrollers with every conceivable form of I/O on the market. The thing that makes the Maximite different is the simplicity of the Basic language, especially for beginners. Now I am not one to shy away from adding features, but I kind of think Ethernet is the other side of the line, not because I don't like it, but because if I want to start working at that level then MMbasic is not the language to do it. There doesn’t seem to be a point in turning the maximite into something that already exists many times over. If MMbasic is too slow or whatever, then graduate to PIC assembler or C or whatever works for you. I guess I think the sort of functionality the Maximite should be aimed at is the equivalent level to Stamp Basic (Parallax gear for those that may not know it) which includes everything spoken about here except Ethernet. The BS2 version is a very capable language, and with the addition of the Maximite's keyboard, VGA and SDcard, it should be the icing on the cake. Of course as Geoff has elected to make the source code open, people are free to do as they wish, but for me, I wouldn't like to see it try and be all things to all people. Regards Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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jebz Regular Member  Joined: 13/06/2011 Location: AustraliaPosts: 79 |
I've looked at the "Maximite Expander" and it's a shame so many of the interfaces are jumpered out of service when you choose analogue, input or output for the port pin. I think if the port from the Maximite had tracks and holes on the bottom of the PCB and the expander had tracks on the top with a grid of non-plated through holes these could enable connections like a pin patch. A number of holes wouldn't be required because some of the functions aren't available on all of the pins. This would enable interface board linking as each board would only link in the devices to the lines that are required. I'd like to see variable gain analogue inputs. Ground independent for current measurement would be good. Digital opto coupled inputs with an isolated dc supply for the external interface side. Relay outputs 2A with isolation from the coil to contact zones. With the pin patch design these interfaces could be made as a fruit salad board containing a few of each. While other boards had say 8 inputs or 8 outputs. . |
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| donmck Guru Joined: 09/06/2011 Location: AustraliaPosts: 1313 |
The fruit salad pin patch design. _________________________________ What signals to use for what I/O is the age old problem, and different users will have different needs. Would you prefer a sting of non plated through holes that you soldered a wire into, or go for an extra .1" of board length, and have a dual row male header, and match signals to I/O with test or shorting shunts or links? Same as hard drive selector links, lots of different names. These are cheap and can be reconfigured pretty quickly if needed. Cheers Don... https://www.dontronics.com |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
The reason this board is a kit and not an assembled product was to allow you to do exactly what you are saying. The fact that the Expander can handle 10 channels each with the ability to handle all the maximite's signal capabilities, does not limit you to having to fully populate the board. Any of the 10 channels can be any function by chosing what components to place. With your suggestion you can only ever have as many inputs or outputs or analogue as you design on the board. The Expander effectively has 30 I/O options, 10 digital in, 10 Digital out and 10 Analog in in any combination, and only limited by the fact that there is only 10 available chanels from the Maximite on the board. And if you want all 20 then add another board and everything doubles. Regards Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
With respect, I disagree. LOTS of people (I'd dare say an increasing proportion of people and applications) will want to collect and share their data. And doing that over RS232 or USB is an increasingly cumbersome and expensive way to do it. Most people now have ethernet for their adsl modems, and wireless access points etc. Its a good, universal standard, ideal for moving reasonably large amounts of data in very short time with relatively high data integrity and very low overheads for checksums etc. Not that it's my call of course! I don't have a maximite (yet). No ethernet is (for me) a deal-breaker. (I just purchased 6 ethernet-enabled boards that are "kinda similar" to the maximite but without kb or vga (but with lots of other things I need more - onewire support etc) |
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| rhamer Senior Member Joined: 06/06/2011 Location: AustraliaPosts: 174 |
So we agree, you need ethernet, 1Wire etc, and have chosen a product that suits your needs. Why then would you want to turn the Maximite into something you can already buy? Altronics have sold well over 500 of these units, and they have created considerable interest. But why, when much more capable boards have been around for years? My view from talking to people who have purchased one is because they are simple (the Maximite, not the people) and they can programatically turn stuff on and off without having to learn a language like assembler or C. Adding ethernet is adding something that these folk don't understand and don't want to learn. If they did they would buy the same product you have. Also the RS232 cable length can be overcome in several ways including RS485 or serial to ethernet converters. Regards Rohan Rohan Hamer HAMFIELD Software & Hardware Solutions Makers of the Maximite Expander. http://www.hamfield.com.au |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah sorry Ross but I tend to agree with Rohan. While I myself would find a ethernet enabled Maximite useful, I think we need to remember what the Maximite is: A small computer that runs BASIC and has 20 I/O pins. Yes there are other PIC32 based controllers out there that are cheaper and/or more powerful, but the Maximite isn't trying to compete with them. I like the Maximite because all its needs is a screen, a keyboard, and uses a language I'm familiar with. I can switch it on and write a program, without any other hardware or software. For a place like this web site, its a perfect little universal computer that could be used for a range of projects, for beginner and old hands alike. You can use the one Maximite computer for several projects, just plug in a different I/O board, swap the SD card, and its a whole different machine. I think if Geoff can get serial comms working, especially I2C, then it wont be long before you can find an add on board that will do anything you want. Like I've said, the only thing I would really like to see is PWM out, but I can use a 08M chip to do that via I2C. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| RossW Guru Joined: 25/02/2006 Location: AustraliaPosts: 495 |
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