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Forum Index : Microcontroller and PC projects : PicoMiteVGA: Stand-alone Keyboard Form-factor
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| lizby Guru  Joined: 17/05/2016 Location: United StatesPosts: 3019 |
Maxi/MicroMite variations: MaxiMite, Colour MaxiMite (CMM/CMM1), MX150 MicroMite (MM1), MX170 MicroMite (MM2), MX470 MicroMite Plus (MM+), PIC32MZ MicroMite eXtreme (MMX), MMBasic for DOS, Pi-cromite (pi-based, no longer supported, may work for non-gpio uses), Armmite H7, Armmite L4, Armmite F4, Colour Maximite 2 (CMM2), Picomite, MMB4L (Linux--currently in Alpha), PicoMiteVGA, MMBasic for Windows (MMB4W)--currently in Beta, WebMite. If you want VGA, PicoMiteVGA is what's current. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3672 |
CMM2 is vastly more powerful. Unsurprisingly costs more too. It can drive serial. John |
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Hawk Senior Member  Joined: 15/07/2021 Location: AustraliaPosts: 141 |
Yep, that's why I'm here, the PicoMite VGA offers just about everything that I'm looking for in a Boot-to-BASIC platform, including an active community. I'm just trying to work out how to develop stuff, both hardware and software, within the current in hardware framework. |
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| Hawk Senior Member Joined: 15/07/2021 Location: AustraliaPosts: 141 |
OK so I finally finished my Silicon Chip kit build. It was super easy, right up to the point where they left the 2N7000s out of the kit. At first I wondered why the keyboard wasn't working. I worried that my power supply wasn't big enough. Then I noticed the empty holes! Luckily I had some on hand from another project. Anyway, here it is all setup and operational.  No sound (of course) and I haven't configured the SD card yet. Time to learn how this baby works! One of the first things that I did notice is that the fonts are different sizes in Mode 2. The test printed from the program is one size, but the text typed in at the command prompt is a larger size. That was unexpected. |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 1805 |
Mode 1 is 640 x 480 and Mode 2 is effectively 320 x 240 so the console font is double size. Console font size can be adjusted. OPTION LCDPANEL CONSOLE [font [, fc [,bc]]] Configures the VGA display The arguments are optional but if supplied must be numbers for use as the console output. , 'font' is the default font, 'fc' is the default foreground colour, 'bc' is the default background colour. The default (after first flashing the firmware) is: OPTION LCDPANEL CONSOLE 1, RGB(white), RGB(black) Edited 2023-04-25 18:42 by phil99 |
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| Hawk Senior Member Joined: 15/07/2021 Location: AustraliaPosts: 141 |
Thanks Phil, I knew it could be changed, I just didn't expect the font from the output of the program to be different from the console font. It certainly wasn't for Mode 1. These are the nuances that I will get to know. I'm very excited to be programming on the actual hardware, and look forward to seeing what I can create. The final build I wish to make will have stereo audio, RTC, controllers and hopefully serial port with hardware flow control. Fonts are probably the least of my worries. ;^) Cheers. Edited 2023-04-26 12:08 by Hawk |
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| Hawk Senior Member Joined: 15/07/2021 Location: AustraliaPosts: 141 |
Following up from an earlier comment by @Mixel90 about reliable availablity of PS/2 keyboards to justify designing a stand-alone form-factor around, I contacted Perixx regarding the future of their PERIBOARD-409 keyboards. I'm happy to say that it sounds like they will be available for some time into the future. If they stop selling the PS/2 version, the USB version will work with a PS/2 adaptor, indicating that it supports both protocols. See their response below. This means that any stand-alone design that is based around this keyboard will be able to be replicated by other people. My plan is to wire the keyboard internally, preferably to a keyed header connector of some description. Progress is still being made on mounting the whole keyboard into the top of the 3D printed case so that it is secure. There are some stand-alone computer designs out there for the MiSTer which have the keyboard just resting in the case. That is not the type of design I'm aiming for here. Hawk |
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| Hawk Senior Member Joined: 15/07/2021 Location: AustraliaPosts: 141 |
OK, so I've just found @matherp's original thread regarding creating a PicoMiteVGA that fits inside a keyboard. Thinking about a new Pico PCB design for integrating into a keyboard Not surprisingly, many of his original design requirements were similar to my own. In addition to matherp's original list, I would add a power switch, as I am already sick of plugging and unplugging the microUSB connector into the Pico, and I would include on-board audio as well as an external 3.5mm stereo jack to output audio to a monitor or other device. I'm happy with a microSD card (although difficult to solder...maybe use a standard Aliexpress module) but would use an extension to remotely mount an SD socket on the right side of the case. I am planning to 3D print the case top and bottom, so I am not limited to what I can fit in the original keyboard case. As mentioned in a previous post, I would also like to fit small stereo laptop speakers, however I have yet to source the rubber mounting grommets that are used to reduce the vibration in the case. As much as possible, I would like through hole mounted components that would allow a beginner/average enthusiest to be able to construct it. There may be choices where an Aliexpress module could be replaced by SMD components on the board at the builders wish. I've seen this done on other designs, specially for level shifters. Anyway, sorry if my thread regurgitated previous topics. Hawk. Edited 2023-05-04 14:10 by Hawk |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5749 |
I like to keep my options open. TBH I'm not incredibly happy about using ebay / AliExpress modules unless my PCB will also accept something else - possibly a SMD microSD socket from a "proper" manufacturer. It's a bit more of a fiddle for me, but it means that my PCB design isn't at the whim of some small company in China. I used a bit of overkill on the PicoGAME, which can have two different level shifters (or none) and any of three different SD card systems. :) Don't feel too bad about the normal standard size SD card socket and SMD audio jacks that have been used on several projects here. They are relatively easy to get and are easy to solder. You might get away with using silicone tubing instead of grommets. Cut the hole bigger than the speaker by the thickness of the tube then slit the tube down its length and push it onto the inside edge of the hole to form a grommet. Silicone tube is fairly soft. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Hawk Senior Member Joined: 15/07/2021 Location: AustraliaPosts: 141 |
Thanks for your opinion. I understand that if you’re use to working as a hardware designer in a commercial environment, you would be used to avoiding sole source suppliers. The advantage here is that the sorts of modules that I’m referring to are supplied by numerous Chinese electronics suppliers, they all copy each other. It allows SMDs to be used in a through hole module that is easier for hobbyists to solder. It also avoids having to source lots of individual components. I would consider modules for RTC, Level shifters, possibly audio amplifier, and external SD card slot. I’m not sure about the microSD socket yet. I know that I can get microSD to SD extender ribbon cables, but I’m not sure about SD to SD extenders. I have a preference for SD cards, as they are easier to insert and remove and also label. They are ample small enough for this sort of design, and if people prefer microSD, they can always use an adaptor. SD to microSD adaptors are not as easy to come by. I love your idea of using the silicon tube as a vibration mounting grommet. I am looking at possible speakers to use, but I need to decide what power output a computer mounted speaker should need. I’m guessing no more than 3W. They can be bought in small plastic enclosures with wires attached, ready to mount. I just need to decide on a model and order some so that I can design the case top to fit them. That will probably also dictate what header to put on the PCB to connect the speakers. I am more than happy to accept your ideas about this design. While some of the components will be obvious, like the VGA output and I/O interface, others have many options, like the power switch and reset switch. I have a preference to an external power input rather than connecting directly to the Pico, and I would want to disable the Pico’s 3V3 regulator and have an external one to improve audio quality. I need to put all my ideas and notes into a document that I can share so others can see my vision. Mostly they’re in this thread, but sometimes a picture can say a lot. Hawk. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5749 |
Be careful if using microSD card modules. Try to get one that doesn't incorporate a regulator or resistors - there are less around than you may think. Generally if it's specified as being "for Arduino" then look very closely! Some of the modules with regulators work, other's don't and some are marginal. Those with pullup resistors actually have the wrong value but they seem to work. Those with series resistors rarely work. The full size SDcard socket that I've used ( DM1AA-SF-PEJ(72) ) is very easy to solder. Disabling the switching supply and using a 3V3 linear regulator is dead easy. Just connect 3V3_EN to GND and feed the regulator into 3V3. In the average living room, with even low efficiency speakers, you don't need more than 1W per channel. It's plenty loud enough for games or most desktop music. If you want a headphone socket then your choice of amplifier is very limited unless you do some fiddling. Which reminds me, I have some audio chips to play with... I have mixed feelings about building speakers in. It's neat, but it limits your options such a lot. There are far better cheap desktop speakers than you can build into a keyboard. Maybe, with a line output jack and a switch to disconnect the internal speakers. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Hawk Senior Member Joined: 15/07/2021 Location: AustraliaPosts: 141 |
A quick search shows me that SD to SD extension modules are available, so the option for the full sized socket is a good one. The SD card could be mounted on the left side of the PCB (and thus the case) but I'm right-handed and find inserting it on the right side of the case easier. The left side of the case could have a volume control fitted. The preference is for this to be a low profile horizontal variable resistor. It could be mounted on the main PCB or a sub module. Yeah, I've read that this is not difficult. The question would be what voltage to input to the computer? Would you fit a 5V regulator, or rely on the quality of the USB-C plug pack? Or would you input a higher voltage and regulate it down to 5V (and 3,3)? Do you have any pointers to the sort of desktop speakers you had in mind? I was considering something as small as these: 2W 8ohm LCD/Monitor Speakers, I think in general, speakers sound better when they are not driven near their limit. Hawk |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5749 |
I'd run it from 5V, personally. Less room for error. I personally favour powering my boards via a 3.5/1.35mm barrel jack. They are easy to work with, easy to get leads for, robust and intended for 5V power. They also can't get confused with the bigger sizes usually used for 9V and 12V. You still need access to the USB connector on the Pico as well though. No ideas about internal speakers at all. TBH I don't even use the ones on my tellys unless I really have to because, to my ear, they all sound c**p! :) At the end of the day you can't get anything below about 150Hz-200Hz out of a tiny speaker cone no matter what you do. Physics won't allow it unless the cone is sealed to your ear to form a pressure driver. If you use built-in speakers then your amplifiers will be running from 5V (unless you use a higher voltage input, in which case you will probably need a heatsink on the regulator). At 5V all the little amplifier chips are bridge types and are not considered suitable for driving headphones. (I have experiments to do on this). Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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