Hi Laurent, On Wed, May 30, 2018 at 03:38:01PM +0300, Laurent Pinchart wrote: > Hi Jacopo, > > On Wednesday, 30 May 2018 15:23:43 EEST jacopo mondi wrote: > > On Wed, May 30, 2018 at 02:52:31PM +0300, Laurent Pinchart wrote: > > > On Wednesday, 30 May 2018 12:30:49 EEST Geert Uytterhoeven wrote: > > >> On Wed, May 30, 2018 at 11:13 AM, Jacopo Mondi wrote: > > >>> The TW9910 PDN gpio (power down) is listed as active high in the chip > > >>> manual. It turns out it is actually active low as when set to physical > > >>> level 0 it actually turns the video decoder power off. > > >> > > >> So the picture "Typical TW9910 External Circuitry" in the datasheet, > > >> which ties PDN to GND permanently, is wrong? > > > > Also the definition of PDN pin in TW9910 manual, as reported by Laurent made > > me think the pin had to stay in logical state 1 to have the chip powered > > down. That's why my initial 'ACTIVE_HIGH' flag. The chip was not > > recognized, but I thought it was a local problem of the Migo-R board I > > was using. > > > > Then one day I tried inverting the pin active state just to be sure, > > and it started being fully operational :/ > > > > > The SH PTT2 line is connected directory to the TW9910 PDN signal, without > > > any inverter on the board. The PDN signal is clearly documented as > > > active-high in the TW9910 datasheet. Something is thus weird. > > > > I suspect the 'active high' definition in datasheet is different from > > our understanding. Their 'active' means the chip is operational, which > > is not what one would expect from a powerdown pin. > > > > > Jacopo, is it possible to measure the PDN signal on the board as close as > > > possible to the TW9910 to see if it works as expected ? > > > > Not for me. The board is in Japan and my multimeter doesn't have cables > > that long, unfortunately. > > How about trying that during your next trip to Japan ? :-) Ok, I'll stop looking for cables 10.000km long on amazon. > > -- > Regards, > > Laurent Pinchart > > >
Attachment:
signature.asc
Description: PGP signature
