I would like to revisit an earlier posting about controlling LCD brightness on the AM3517 EVM. I'm starting a new thread because the original thread referenced a different board name (AM3715), although I suspect that was a mistake.
In the original posting the poster noted that changing the LCD brightness through the Android Settings menu had no effect on LCD brightness, and he questioned if hardware support was present. The TI response said "Brightness control is not functional on AM3517evm running on froyo. This is because HW does not support brightness control." That original posting is at http://e2e.ti.com/support/embedded/f/509/p/85680/297554.aspx .
However, looking at the AM3517 EVM Rev C circuit, it appears to us that the board does in fact have hardware support to control LCD brightness. GPIO181 drives the enable pin of the LCD's backlight boost regulator (TI's TPS61040). The TPS61040 datasheet suggests that brightness control can be achieved with a PWM signal on the enable pin. Since GPIO181 can be configured to generate a PWM signal, would this not constitute hardware support for LCD brightness control?
Also, if hardware brightness control is in fact present, can you confirm whether software support for controlling brightness is provided or not in the TI Gingerbread 2.3.4 distribution? As observed by the original poster using Froyo, we see no effect on the brightness with Gingerbread, when setting the brightness level through the Android Settings menu.
Ron
