How you directly access serially chained devices, like LEDS, shift registers, etc?

[richard]

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

[CuriousOne]

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.

[richard]

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.

apa102 16million colours, 32 level global power control
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

[CuriousOne]

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 huge in 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.

[HenrikOlsson]

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.

[richard]

192x12x3=6912 bits == 864 bytes

[CuriousOne]

Each color value is 8 bit, so it is 6912 bytes, not bits But that's ok, I'll use external EEPROM as display buffer.
MSSP would be great, but no PBP support as far as I know - need to use ASM....