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Forum Index : Microcontroller and PC projects : PicoMite: PicoGAME VGA development
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
Thanks Mick (& Volhout), good to know that there are options. If you have a file system it's quite useful to be able to tell when a file was created/modified. ACK. They arrived this morning just as I was going away for a few days but will measure then when I get back ... I can christen the manual Vernier caliper I got for Christmas, requested as much as an object of elegant beauty rather than having any particular need for it. Good work Mick. I have a question about the analogue PC flightstick option (not the thumbstick). That is intended to plug into B (on the prototype board) but how is it supposed to work, diagrams i've found online show these sticks to generally be 15 pin and wired significantly differently to an old fashioned Atari digital stick which is what the PCB is marked up for. Am I looking at the wrong thing, or just having a funny turn? Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
The analogue sticks don't seem to be quite as standardised as the digital sticks. The official PC Flightstick was, IIRC, on a 15-pin connector which had 4x analogue ports on it (using 555-based circuits) but I remember seeing adapters that split the 15-pin port into 2x 9-pin ports. There were also 9-pin analogue joysticks made for other platforms (the one I have is one of these - I just can't find it at the moment). The circuit of the majority of analogue sticks is, I think, based on the above "paddle" circuit. There is a variable resistor (not a potentiometer like JS1) connected between supply and the analogue input. Originally this was a 5V supply and the resistor was the timing resistor for a 555 monostable. Software reset the monostable then measured the time taken for it to trigger. That gave the paddle position. I'm not doing that. :) I'm putting the resistor between 3V3 and the input, with a pull-down resistor. I can then simply read the analogue input to get the position. The analogue inputs are on pins 5 and 9 of port B and pin 9 of port A. That's why JS1 has to go on Port B - it needs two inputs. I'm toying with the idea of using a single analogue port for a joystick and switching it between x and y axis. That would be done in the joystick box, not on the board, and would use two of the digital pins and a couple of mosfets or something to do the switching. It would allow three analogue joysticks at the same time (two of them on port B). Whether the read time of the ADC would be of importance I don't know. Just a vague idea at the moment. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
Thanks for the idea, Volhout. The level shifter can now use MOSFETs and resistors instead of a module. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| al18 Senior Member  Joined: 06/07/2019 Location: United StatesPosts: 205 |
Mick, Thanks for allowing the use of MOSFETs and resistors - now I can use those extra parts I bought for the PicoMiteVGA! |
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| al18 Senior Member Joined: 06/07/2019 Location: United StatesPosts: 205 |
Mick, I hope you are keeping the footprint for the LM TO-220 regulator and caps on your revised board, because I just found two of my sources have no stock and are quoting 2-7 months lead-time on the MCP1700 3.3V. The only alternate I found was the MCP1701 3.3V, but that only outputs 150 mA - probably not enough. |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
I bought my MCP1700s for peanuts on AliExpress though a Google through the undergrowth now indicates they may be "fakes" - my first if that is the case, is there some sort of initiation ceremony? Can anyone suggest a simple circuit/procedure for testing them? Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
The TO-220 reg feeds the 5V rail, not the 3V3. The keyboard supply is on the output of that reg, so if you put a 3V3 reg in there you'll need a keyboard that will run from 3V3 and link out the level shifting circuit. It's all fiddlable, I suppose. I need to check the current with the controllers on, but at the moment it's less than 100mA while playing music. The MCP1701 would probably just about do. I've just bought a few MCP1700s from my usual source. I'll look for alternatives. You will be able to build the board without that reg anyway, by re-enabling the SMPS. Headphone audio will definitely suffer though. I'm just considering a change. At the moment GP15 switches Port B between Controller and Joystick modes because pin 6 has to be a 3V3 supply for a controller and is the trigger input for a joystick. The current output from pin 6 is limited by a 68R resistor to about 45mA max (in practice it's lower because of other things - about 35mA IIRC). The change I'm considering is to get rid of the LED and use a constant current source of about 35mA to feed the pin at 3V3. There would be no need to switch modes then. Even a tactile switch can handle 35mA safely (they are usually rated to 50mA @ 12V, but as the current increases the life goes down). As I said, I need to check the current needed for a Controller, but if it's less than 35mA this is a possibility. That would probably give a maximum load of about 170mA with two controllers, but it might still be appreciably less. EDIT: Just added solder blob links that can connect the keyboard supply to the input of U1 rather than the output. This will allow U1 to be the main regulator for the 3V3 supply, but the input voltage mustn't exceed 5V so it will have to be a 78xx compatible LDO. EDIT EDIT: The Controllers draw a very low current. A 150mA reg will almost certainly work fine. . Edited 2022-04-20 17:32 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| al18 Senior Member Joined: 06/07/2019 Location: United StatesPosts: 205 |
Ok, thanks for the update. I ordered nearly all the parts yesterday except for the MCP1700 3.3V and the bicolor LED - couldn’t find a 3 mm version. I also didn’t buy the side mounted USB port because it’s setup for 5v output and didn’t think I would need that. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
Don't worry too much about those bits. If you have a 78xx compatible LDO reg you can use that with some fiddling. Making the SMPS work is a bit more fiddly as the 3EN pin is linked to GND on the bottom of the board and you have to dig the link out. Then you can connect VSYS to 5V and get a 3V3 output. It's best to do that mod before you even consider mounting anything on the board. The polarity of the USB-A port is wrong anyway. Make sure you read my notes. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| al18 Senior Member Joined: 06/07/2019 Location: United StatesPosts: 205 |
Ok. Just getting prepared for the next board release… |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
Bumping this since I'm hoping it was missed and somebody can help: Also I'm making progress on the "launch title" I promised Mick. If there is anyone who can help with music then I'd appreciate it: https://youtu.be/Q9_FxvCC3v0 Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
The MCP1700 is rated at 250mA for voltages over 2.5V, but we don't need that much. I'd put one in a breadboard and put 5V on its input with a small capacitor then load the output with two 33R resistors and another in parallel. The output should be at 3V3 as the load will be 200mA. The capacitors should be 1uF ceramic ideally, but 10uF electrolytic should be fine. Removing one of the resistors shouldn't change the voltage by very much at all. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| al18 Senior Member Joined: 06/07/2019 Location: United StatesPosts: 205 |
Tom, Looks like a good start. GLTron is my favorite version of this game, released about 20 years ago. http://www.gltron.org/index.php |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
I've used Circuit Simulator to simulate a joystick that uses a single analogue input with the X and Y axis voltages switched to it using P-channel mosfets. Each gate is connected to one of the GP pins so the board can read one or the other. It seems to work remarkably well, but I can't build it. I've no P-channel mosfets and no-one that handles small quantities seems to have any. :( I can get them from Mouser, Farnell, Digikey etc. but we're back to the stupid handling and postage charges again. :( EDIT: RS to the rescue. Their postage is far more reasonable. They have the white version of the Hammond case in stock too (229-1681). Hopefully I'll be able to test my analogue joystick idea very soon as the mosfets should arrive tomorrow (while I'm out all day, of course). Edited 2022-04-21 20:29 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
Slight changes to the next version today. Port A now has GP26 and GP27 on it, Port B has GP28. This has allowed an interesting change. If no connections are being used on GP26 and GP27 then an optional RTC module (the little one) can be plugged into its own header. You can't then use these pins for analogue or use JS1, but all other functions of both ports are still ok. No hardware configuration on the board is necessary to do this other than set the GP26 and GP27 links on LB1 to UP. GP15 has been wired to Port B as a Fire input. This would allow an analogue paddle controller on each port, each having a paddle knob and a fire/trigger button. The pin 6 3V3/trigger supplies are both current limited to 33mA max. I may be able to reduce this further yet. The pin 7 3V3 supplies aren't (apart from any regulator current limit). Edited 2022-04-22 05:52 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6821 |
Hmmm.... My testing and QA could have been a lot better. lol! Red and Blue are wrong way round. Best way to get round this on the prototype is to put R10 and Rll in so that they cross over. I know it looks messy, but it's a prototype. Either that or hack the PCB (not bad to do, and much neater as it's all on the bottom). This will definitely be fixed on the next version! :) I've put one of the prototype boards into the Hammond case now. It was very fiddly as, of course, you can only mark out on the inside (where iit's shiny and markings don't show up) and drill from the outside. :( Hopefully I'll be able to sort out some proper dimensioned drawings now for cutting out the end plates and side holes. It looks pretty good, I think, especially for a first attempt. Incidentally, the Hammond cases don't come with PCB fixing screws. They are No.4 x 6mm self tapping screws. I used all 8 on the prototype, but on the new version one would be blocked off by the SDcard so I'm not bothering with that one. TBH 4 is almost certainly enough unless you are really rough with the connectors. Edited 2022-04-23 07:05 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4262 |
Tom, What is your intention about the music?. Do you envision to play tones, a tune thay is composed? From a midi file? For Tetris, I recorded a sound from a gameboy in the correct wav format. That was easier. Volhout PicomiteVGA PETSCII ROBOTS |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 4047 |
Hmm, you're failing to recognise how useless I am. I was trying to learn some basic electronics, but people keep creating boot to BASIC machines that I end up playing with instead. I built this circuit, which I think is what you described:  I had to use 47R resistors as I don't have any 33R. The output from the MCP1700 was in the range 3.3V-3.5V and the current about 100 mA which I guess is about right given that resistor network has a resistance of about 30R according to my memory of basic theory. Does this sound OK, the regulator was pretty warm (but not hot), should it have been ? In the quoted text how is the load 200 mA ? A network of 33R resistors as you describe has a resistance of 22R and 3.3 / 22 => 150 mA doesn't it ? Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1611 |
I think what Mick meant to say was to use two 33 ohm resistors in parallel as the load. One will take 100mA and two will take 200mA. Yes it should get warm, I wouldn't leave a 200mA load on it for too long without a heatsink of some sort. Bill Keep safe. Live long and prosper. |
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| Turbo46 Guru Joined: 24/12/2017 Location: AustraliaPosts: 1611 |
You could try three 47 ohm resistors in parallel, that will give you a load resistance of a bit more than 15 ohms. Bill Keep safe. Live long and prosper. |
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