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hzeller / rpi-rgb-led-matrix

Controlling up to three chains of 64x64, 32x32, 16x32 or similar RGB LED displays using Raspberry Pi GPIO
GNU General Public License v2.0
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Support for 16x64 displays #96

Closed lanrat closed 8 years ago

lanrat commented 8 years ago

Moving the discussion from pull #88 here.

What is the purpose of double_rows_(rows / 2) in framebuffer.cc (https://github.com/hzeller/rpi-rgb-led-matrix/blob/master/lib/framebuffer.cc#L55)? When changing to double_rows_(rows) my display works perfectly with rows=16 and chain=2. Should this be made into a variable that can be controlled in the API?

lanrat commented 8 years ago

You can view the change I made to work on my display here: https://github.com/lanrat/rpi-rgb-led-matrix/commit/9c11e9937c233da33928e9ee72e9a0ef3e956400

I think that this should be user-configurable and not hard-coded, but I don't understand it well enough to be sure.

hzeller commented 8 years ago

Replacing the rows/2 with rows would work in your case. I need to think about a way to configure that that the documentation is still understandable :)

In general, this is just a special case of only using half a 32 high display (as you already have seen in the pictures of your pull request).

Which means - did you notice that with that display, you have the opportunity to connect up to 6 chains ? Usually, one display gets both R1G1B1 and R2G2B2. Now, you connect the first to the first display, the second to the next display. So each previous single chain can be split in two.

So, if you have a split chain with two 64x16 displays, (first connected to R1G1B1, second to R2G2B2, all the other signals A,B,C,D, Strobe, Clk etc connected to both), you can say rows=32 and chain=2 and essentially get a 64x32 display.

If you go with -P3, you can have up to 64x96 pixels (and of course, each chain can be longer, so you can have multiple of 64 in x-axis direction).

Do you have a close-up picture of the connector on your board ? (similar to https://github.com/hzeller/rpi-rgb-led-matrix/blob/master/img/hub75-other.jpg ). Hopefully, it has some readable description. I'd like to add that case to the documentation.

lanrat commented 8 years ago

Here is a photo of the connector on my display 2015-12-02 19 00 02

I only have 1 display which I bought off ebay with no documentation, so I had no idea how it works, let alone the amount of displays that can be chained. I'm also using a Raspberry Pi B so I have no parallel support.

hzeller commented 8 years ago

Thanks for the picture - it looks like it is pretty different from the 'usual' connector, yet the electric stuff seems to work similarly. Anyway, thanks to each display only 'half' a 32 display, you now have parallel support for two chains :)