Hi, On Fri, Jan 12, 2018 at 10:18:39AM +0800, Yong wrote: > > On Thu, Jan 11, 2018 at 09:15:08AM +0800, Yong wrote: > > > > On Mon, Jan 08, 2018 at 05:13:39PM +0000, Hugues FRUCHET wrote: > > > > > I'm using a ST board with OV5640 wired in parallel bus output in order > > > > > to interface to my STM32 DCMI parallel interface. > > > > > Perhaps could you describe your setup so I could help on understanding > > > > > the problem on your side. From my past experience with this sensor > > > > > module, you can first check hsync/vsync polarities, the datasheet is > > > > > buggy on VSYNC polarity as documented in patch 4/5. > > > > > > > > It turns out that it was indeed a polarity issue. > > > > > > > > It looks like that in order to operate properly, I need to setup the > > > > opposite polarity on HSYNC and VSYNC on the interface. I looked at the > > > > signals under a scope, and VSYNC is obviously inversed as you > > > > described. HSYNC, I'm not so sure since the HBLANK period seems very > > > > long, almost a line. > > > > > > > > Since VSYNC at least looks correct, I'd be inclined to think that the > > > > polarity is inversed on at least the SoC I'm using it on. > > > > > > > > Yong, did you test the V3S CSI driver with a parallel interface? With > > > > what sensor driver? Have you found some polarities issues like this? > > > > > > Did you try it with Allwinner SoCs? > > > > Yes, on an H3. Looking at all the Allwinner datasheet I could get my > > hands on, they are all documented in the same way. However, I really > > start to wonder whether the polarity shouldn't be reversed. > > > > At least the fact that VSYNC is clearly active low on the > > oscilloscope, while I have to set it active high in the controller > > seems like a strong hint :) > > The BSP code of Allwinner also treat V4L2_MBUS_VSYNC_ACTIVE_HIGH as > they documented 'positive'. > Maybe there need some more tests to confirm if the datasheet and BSP > code are both wrong. Indeed, and at the same time they do the same on the ov5640 driver they have. I really think they are in a situation where they report that both the interface and the sensor are active high, while they are actually active low, but since both sides still use the same polarity it works. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
Attachment:
signature.asc
Description: PGP signature
