7" Diagonal - 1280x800 IPS Display - HDMI Timings for Raspberry Pi

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daviddever
 
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7" Diagonal - 1280x800 IPS Display - HDMI Timings for Raspberry Pi

Post by daviddever »

I recently acquired a 7" Diagonal - 1280x800 IPS Display from Adafruit, which looks great–I am quite pleased with its display quality and functionality. That said, it seems that custom timings are required to properly drive the display (pixel-accurate) at the native panel resolution via the HDMI input.

As I'd planned on using this display with both the RPi model B and a BeagleBoneBlack, I figured it'd be worth testing using the modes listed within the RPi FAQ. However, the display itself it not natively supported (e.g., pixel-for-pixel) using either DMT or CEA modes.

So–having already tried it with a VGA input on the Mac, I used SwitchResX (http://www.madrau.com/indexSRX4.html), along with the HSD070PWW1-B datasheet (http://www.adafruit.com/datasheets/HSD070PWW1-B00.pdf), to determine the necessary HDMI timings listed below (using the DMT group).

Horizontal Blanking Time = front porch + sync pulse + back porch = 160
1 Line Scanning Time = Horizontal Blanking Time + Horizontal Display Time = 1440
Vertical Blanking Time = front porch + sync pulse + back porch = 23
Frame Period = Vertical Blanking Time + Vertical Display Time = 823

gives the following lines to be used for the RPi config.txt

hdmi_group=2
hdmi_mode=87
hdmi_timings=1280 0 48 32 80 800 0 3 6 14 0 0 0 60 0 71000000 5

In real-world language, this corresponds to:

Horizontal active area, in pixels: 1280 [Horizontal Display Time, from datasheet]
Horizontal sync polarity: 0 [no inversion required]
Horizontal front porch: 48
Horizontal sync pulse: 32
Horizontal back porch: 80
Vertical active area, in pixels: 800 [Vertical Display Time, from datasheet]
Vertical sync polarity: 0 [no inversion required]
Vertical front porch: 3
Vertical sync pulse: 6
Vertical back porch: 14
Vertical sync offset a: 0 [none required]
Vertical sync offset b: 0 [none required]
Pixel rep (?): 0
Frame Rate: 60 [Hz]
Interlaced: 0 [non-interlaced]
Pixel Frequency: 71000000 [71.0 MHz Clock Rate]
Aspect Ratio: 5 [corresponds to 16:10, according to discussion here: http://www.raspberrypi.org/phpBB3/viewt ... 29&t=24679]

As always, your mileage may vary–but I hope this saves someone a bit of time.

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