Post B4GCKl6PqolhSdwkam by sun@shitposter.world
(DIR) More posts by sun@shitposter.world
(DIR) Post #B4GCKl6PqolhSdwkam by sun@shitposter.world
1 likes, 1 repeats
does this diagram make sense? it's supposed to output bitbanged black and white only VGA.I derived it from an ASCII diagram for more or less full color VGA, modified to be just black and white, using less GPIO pins.
(DIR) Post #B4GCtUkEf0tYrc8S4O by vii@dsmc.space
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@sun What happens between GPIO14 and the VGA RGB pins isn’t perfectly clear. I would expect stepping of some sort to split a single pin into three, if not something that results in a really rudimentary fourier transform
(DIR) Post #B4GCtUvE09gZPhHECO by vii@dsmc.space
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@sun goddamnit sorry my fault, I missed the part where you said black-and-white.
(DIR) Post #B4GCtV5rMcBzwgFim8 by sun@shitposter.world
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@vii yeah completely passive conversion to all three channels
(DIR) Post #B4GDm9eklhC7O0dQXI by Soy_Magnus@detroitriotcity.com
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@sun yeah that checks out to me
(DIR) Post #B4GE3aAfRMRKXjsADo by sun@shitposter.world
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@Soy_Magnus thanks, I barely know what I am doing and a unsure about everything.
(DIR) Post #B4GEMn2hoAk5xwJ7fE by Soy_Magnus@detroitriotcity.com
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@sun no worries diagrams suck and are confusing lol
(DIR) Post #B4GFflIYcMDc0oKfK4 by troonigger@clubcyberia.co
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@sun Have you worked out how much current you'll be sinking on those three pins you're driving via GPIO 14?It might be too much for a single GPIO
(DIR) Post #B4GFfldTMawt3g7MvI by sun@shitposter.world
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@troonigger I can reduce the GPIO output impedance by setting the drive strength to 8mA on the pin, then when it's split into three, the voltage is almost exactly what analog VGA expects.
(DIR) Post #B4GFgR5ZF2mdcgZsuG by i@declin.eu
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@sun whenever i have to make up a basic circuit, https://wokwi.com/projects/new/pi-pico really helps, because you can simulate the entire thing quite well and be left with something you could inspect after the fact and versioncould make a whole custom vga display in it https://docs.wokwi.com/chips-api/getting-started
(DIR) Post #B4GG7iFHYsJieV81Jo by tobias@poa.st
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@sunAre you connecting to an old vga monitor?
(DIR) Post #B4GG7iTogpwXNZvcyO by sun@shitposter.world
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@tobias no, I just only needed a black and white picture and wanted to reduce how many gpio pins I was using and reduce build complexity.
(DIR) Post #B4GLOzfmWH4TOcaCDg by troonigger@clubcyberia.co
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@sun it was more whether a single GPIO could source enough current to drive the three VGA pins, they're quite low impedance. Your circuit won't go boom, so it'll be interesting to know if it works. I'm guessing the image will be dark and glitchy.
(DIR) Post #B4GLPFsmFiyPfYmnhI by tobias@poa.st
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@sunok. Look at CGA monochrome mode, which has 2 resolutions.
(DIR) Post #B4GLRGzV6PclgbtR20 by zaitcev@shitposter.world
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@sun The diagram is okay but I cannot imagine the CPU on Pi being able to do much when not banging (during the frame blank essentially). Do modern Pis have several cores?
(DIR) Post #B4GLRHLplNUMnsLGqG by sun@shitposter.world
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@zaitcev yeah two cores and one is only for the video
(DIR) Post #B4GLUnI9Su4ijaIPMu by sun@shitposter.world
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@troonigger yeah i don't really know what i'm doing
(DIR) Post #B4GM0uPQXRuc4i0pd2 by troonigger@clubcyberia.co
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@sun just try it, if it looks like crap then use three pins. half the fun is trying stuff out.