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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
Actually, I'm not doing anything so far, just in future, I want to make a small RGB display, 192 X 12 pixels, using these LEDs. My experience with 64x8 LED displays, based on 4 x MAX7219 was not so good, because this "serial" method of needing to update everything at each time, required complete re-send of data to display, which was quite lagging, and won't allow to do some cool animation or smooth scrolling.
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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
18F46K40 can run at least 4 of these 16x32 [512led] modules, possibly 6
@25 fps(as a back ground task)
two colour
full 24bit rgb on esp8266
Last edited by richard; - 22nd January 2022 at 10:11.
Warning I'm not a teacher
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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
It is not about what can run what, it is about efficiency.
As another solution, I think, led decoders like HT16K33+discrete RGB LED or similar can be used.
With APA102C, 1 shiftout statement updates color of 1 pixel (3 leds )
In case of HT16K33, 3 shiftout statement will update color of 8 pixels (24 leds), so resulting speed will be 8/3=2.6 times higher.
So I'm seeking for solution in that way.
Of course, there are specialized RGB display modules and controllers, but their issue is, that they either have gigantic brightness, or their pixel distance is very sparse. And I want to make compact display for indoor use - discrete RGB leds are available in 0805 package, and APA102C/WS2812 are available in 1206 package.
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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
apa102 16million colours, 32 level global power controlWith APA102C, 1 shiftout statement updates color of 1 pixel (3 leds )
In case of HT16K33, 3 shiftout statement will update color of 8 pixels (24 leds), so resulting speed will be 8/3=2.6 times higher.
HT16K33 8 colours no power control
dmd panels come in p2.5 p3 etc to p10 the number is the pixel grid spacing in mm
dmd panels are just shift registers multiplexed in 4 row pair strings there is no controller as such
if you want the complexity of colour and power level control on a per pixel basis you need to store and transfer
the info to represent it, there is no simple
Warning I'm not a teacher
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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
ht16k33 was just an example, note the "or similar" in my post - I don't exactly remember which holtek chip has individual brightness control, but there are some, they're installed in these commercial color rgb panels.
Yes, 2.5mm spacing, that is hugein 2.5 x 2.5 mm area, where you will have 4 RGB pixels, with SMT leds, you can have 3x3 or even 4x4 RGB pixels.
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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
Since the LEDs effectively ARE shift registers daisychained together there is no way to update a single LED, you doneed to refresh the complete string. But if you design a 192x12 display you could, for example have 12 separate strings of 192 leds so that you could update the display row by row - if that helps.
You'll need a PIC with lots of RAM though, 192x12x3=6912 bytes to hold the display data.
And, since you talk about efficiency, forget SHIFTOUT and start using the MSSP module or the SPI module on the newer PICs instead.
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Re: How you directly access serially chained devices, like LEDS, shift registers, etc
192x12x3=6912 bits == 864 bytes
Warning I'm not a teacher
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