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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: 3863 |
Another question, is there a reason it is powered from a barrel jack and not a USB-A (or B) ? Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| al18 Senior Member  Joined: 06/07/2019 Location: United StatesPosts: 175 |
Looks great! I agree D1 should be a Schottky rectifier diode such as 1N5819 |
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| al18 Senior Member Joined: 06/07/2019 Location: United StatesPosts: 175 |
Is JS1 a connection for a DS3231 RTC? I didn't see it shown on your schematic. |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5768 |
The funny joystick thing is a module for those who prefer not to use a case (or don't mind cutting a suitable hole - or whatever). It's completely optional and doesn't affect the rest of the design. The little barrel jack is a good one, in my estimation. Leads that connect it to USB-A plugs are easy to get an let you plug it into just about any USB supply. These are designed as power supply connectors, unlike USB-A and USB-B. As this device is intended to allow connection to higher voltages than USB (if U1 is fitted) I thought it would be a good idea to use it in this case as I don't fancy the idea of putting 12V or 24V on USB stuff. Something will go wrong somewhere! Note that I didn't use the more common size that is often used for 12V - I don't want tears. JS1 is the joystick module. It plugs into that connector if you use a version with male pins on the back. There is no RTC on this board as there are no pins allocated to I2C. D1 can be whatever you like in this case. :) Supply in is at 5V and regulated down to 3V3 for the PicoMite and most other stuff. The keyboard gets the full 5V, but that's unlikely to be too fussy. I happen to have a lot of 1N400x diodes and the difference of 0.2V doesn't worry me in the least (it depends on current draw anyway). USB leads are *far* worse for volt drop. 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: 175 |
Ok, thanks for incorporating the 5 pin header for JS1 connector - makes sense. The round circle next to JS1 threw me off - looked like an outline for a CR2032 battery common on RTC. The DC power jack is a good idea - hopefully the jack footprint will fit the 2.1 mm x 5.5 mm DC jacks I just bought a quantity of (used on Peter's PicoMiteVGA board). |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5768 |
I happen to have a few of the smaller size because that's what I included in my design for the VGA mini version of the PicoMite VGA. :) No idea if the footprint is anything like the same. I doubt it. I doubt if you can fit the bigger connector in that position at all - it's very tight on the front and back panels. 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: 5768 |
Latest: DB9F connectors now officially known as Port A and Port B. Changed port connectors to some from RS. Changed multiturn pot to 6mm preset + resistor - easier to get, I think. Added safety resistor & capacitor for pin 6 of port B (same as port A). Added space for an incoming supply electrolytic prior to U1. Renumbered the capacitors so that it makes more sense. Corrected circuit of power section to match PCB. Solder blob link added so that Port B can be fixed in PC mode. Tidied a few traces up. ADC inputs can now have pull-up, pull-down or no resistors. Links added. Am concerned about the LED - not many will fit in that space! I think the BOM is almost ready now. It's part of a brief instruction sheet. 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: 175 |
The joystick connectors need to be DB9M. FYI joysticks have a DB9F connector at the end of the cable. I would prefer to see headers and a shunt jumper to select PC mode on Port B Will a normal T-1 (3 mm) Bicolor LED fit in the space between the joystick connector? I wouldn't worry about using a right angle LED. |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3863 |
Hi Mick, The NES controllers also have DB9F connectors - without the metal "shields". When you talk about "PC mode" is this the same as "Atari mode" ? 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: 5768 |
Finger trouble in posting - it's designed round DB9M. :) I deliberately kept away from a jumper. If the board is cased it's a pain to keep opening & closing the box for different games. The software approach also allows the possibility of games that will work with either controller. In theory a 3mm LED will fit. There's not a lot of space to play with as I don't think I can move the connectors further apart. I've not got a box or the connectors so I can't be absolutely certain. A flat LED will fit as they are only just over 2mm thick. I have just a few bicolour ones but I'm not sure how easy they are to get now. EDIT: Yes, Tom. I changed it to PC mode as I know the resistance range on those analogue sticks is 0-100k. I'm no certain about Atari sticks, apart from the switch ones, now I'm told that the paddles are 1M. There should be a gap of 3.5mm between the DB9 connectors. Edited 2022-03-24 07:47 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: 175 |
The low cost analog joysticks that I was thinking of have a 10k pot for each axis and a switch when pressed. A typical example is at the surplus electronics store www.allelectronics.com p/n ST-1079 for $1.75 each |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5768 |
That's the one that fits in the JS1 position. :) You can find them easily enough on ebay too. I've not found any with the connector on the back, unfortunately, but they could be connected by leaving off the female connector and direct wiring to the PCB or using duponts on short pieces of wire. EDIT: Modified the LED circuit. It now gives a nice clean switch between red and green - no horrible colour mixing needed. . Edited 2022-03-24 21:47 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: 3585 |
Nothing wrong with a red flat LED and a green flat LED.... Remember that DB9F and DB9M have a different pinout (pin numbers are mirrored). Edited 2022-03-24 22:02 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5768 |
True. A 3mm LED *should* fit though. A bit of sandpaper on the sides would fix it anyway. :) EDIT: Now that's a good point... I'm not sure if I've got them right... . . Time passes... . . Looks like they are ok. I peeped into the ports of a Specrum 128 to see the numbers. :) . Edited 2022-03-24 23:59 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: 5768 |
.... Even more time passes.... Construction pack: PicoGameNES11.zip EDIT: I should have included these pictures in the construction pack really... ebay components.zip . . Edited 2022-03-25 17:12 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3863 |
Thanks Mick, In theory five of them (in glorious red) are on their way on the Slow Boat from China - so I've got a few weeks to work on MMB4L before the distraction begins in earnest. Hope you've left enough room to work on these boards for the inevitable bodge wires and a dead bug or two  .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: 5768 |
Who knows? They are prototypes. :) You can always leave JS1 off - you could almost dead bug a Z80 there... I half considered putting a small sea of holes under the joystick but decided that it simply wasn't worth rerouting everything as the space would have been pretty small. I also wanted to leave it clear just in case there is a future supply issue with the microSD boards - I think I might be able to *just about* squeeze a standard SD card holder in there (losing at least one joystick fixing point, which I'd rather not do). It was only after adding the joystick that I realized how useful it could be, positioned at the LHS of a compact keyboard and used for menu navigation etc. You have to bear in mind that this is still a normal PicoMite VGA and Port A (COM1 TX/RX and an EN pin) could be feeding a RS485 network (albeit via something to translate the 3V3). It can still be a "serious" control computer, especially when powered from a 12V or 24V industrial system. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| thwill Guru Joined: 16/09/2019 Location: United KingdomPosts: 3863 |
I know, but since I proposed this version I'm feeling kind of obliged to be an early adopter. Maybe if I create/port some content then there will be some interest. Fortunately(?) I never put together its big brother (Peter's PCB) so I still have the VGA connectors in my inbox, just have to start rustling up the other components. Not really my remit, I'm not here to be "serious". Best wishes, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 3585 |
Looks good Mick. Only thing I do not understand is the hardwiring of pin 37 to38. Now you are forced to use the linear regulator. You probably use it to get cleaner audio. But replacing C5 and C6 with a silicon diode (same circuit as you do for VGA red and blue), and replacing R6 and R2 with 15n capacitors would also do the job of getting clean audio. Another option would be to use the 2 free channels in the level shifter. These could also give the same functionality, and even increase the audio level. You only would have needed to make sure the voltage at the HV pin was "clean". Regards, Volhout P.S. I am not sure about "serious control computer". Not many IO pins to be serious about. Edited 2022-03-25 20:14 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 5768 |
The current load is so low that it's well within the rating of a cheap linear reg and I *know* it will remove all SMPS noise. There is very little external load in this case - it's not an experimenters board where people are likely to connect loads of LEDs etc. The low level circuit is incidental in my case. I want to drive fairly sensitive 32R headphones. The resistor in series with the headphones limits the headphone current. Because the diaphgragms are then relatively slow to react you get a filter that removes most of the PWM noise. When you consider that, it doesn't really matter what I do with the low level output. I decided to use one that's been tested - I'll probably never use it. :) (Remember that you are looking for a linear sine wave output, ideally. Non-linear diodes and level shifters are not the best idea when what you really want is a low pass filter. :) ) Edit: You have COM1 and a couple of pins on PORT A. That can handle RS485. How many IO do you want? :) Edited 2022-03-25 20:36 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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