Blinkenwall.com: Unterschied zwischen den Versionen
Anlumo (Diskussion | Beiträge) Keine Bearbeitungszusammenfassung |
Anlumo (Diskussion | Beiträge) |
||
| Zeile 120: | Zeile 120: | ||
This is where the real challenge comes in. These panels do not have a controller built in, your have to PWM the rows and columns yourself. The connection is called HUB75, although this is not an official standard per se. There are plenty of explanations available on the web, and it's not very complicated. However, if you want to have more than the primary colors, you can't use an Arduino for it, since it's not fast enough (colors have to be centrally PWMed). You have to send a steady ~7MHz signal, which usually can only be produced by FPGAs. | This is where the real challenge comes in. These panels do not have a controller built in, your have to PWM the rows and columns yourself. The connection is called HUB75, although this is not an official standard per se. There are plenty of explanations available on the web, and it's not very complicated. However, if you want to have more than the primary colors, you can't use an Arduino for it, since it's not fast enough (colors have to be centrally PWMed). You have to send a steady ~7MHz signal, which usually can only be produced by FPGAs. | ||
Panels can be chained, but this reduces the color fidelity (because the input signal is limited to about 7MHz, no matter how many panels are connected. Reduced bandwidth per panel means fewer colors). Also note that these panels need gamma correction, because the perception of LEDs is far from linear. Thus, you need a color depth of about 10bits to get 8bits of real colors. There are a few tricks to alleviate this, for example you can reduce the frame rate to allow more colors, or you can do temporal interpolation. It's a bit of black magic. | |||
Thus, the easiest solution is to connect to each panel individually. | |||
Luckily, this is not the first project to come across this issue. Thus, there are controllers available for this, like [http://www.aliexpress.com/item/New-Arrival-LINSN-RV901-RV908-Full-Color-RGB-LED-Display-Screen-Receiving-Card-Crazy-Price-LED/738813836.html this one] (featuring a Spartan 6 FPGA, surprise surprise). However, documentation is rather sparse, so right now we don't know how you can control them. [[Benutzer:anlumo|anlumo]] is working on a custom Zynq 7020-based solution for controlling these panels, but that project is in the planning stages right now. | |||
It's assumed that the input signal to the controller is HDMI, so any SBC could be used for this, even the existing Raspberry Pi. This would even allow to use the built-in graphics acceleration capabilities, like OpenGL ES or OpenVG. | |||
== Various Links == | == Various Links == | ||