i.MX 6Dual/6Quad Backlight Questions

[scottwalter]

Which registers would one modify to change the backlight or disable it completely? I see mentions of the functionality in the IPU section of the reference manual but can't seem to find any specific registers. I'm trying to write a driver for the HDMI interface on the board I am using with an imx6 processor.

[igorpadykov]

Hi Scott

backlight is serviced by PWM module, not IPU, please check PWM chapter

i.MX_6Dual6Quad_Linux_Reference_Manual.pdf

L3.0.35_4.1.0_LINUX_DOCS

Best regards

chip

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[scottwalter]

I read through the PWM module and it doesn't mention the back light control anywhere. I can assume that the period of the PWM is what effects the brightness of the display, but this isn't mentioned anywhere. Additionally, the reference manual mentions Stop Mode, Doze Mode, and Wait mode and doesn't explain what any of these modes are or what their purpose is. Sorry, I'm not entirely familiar with this technology, could you tell me what I missed? Thanks.

[igorpadykov]

Hi Scott

please look at attached page 288 from this document,

it shows how to disable PWM.

Regarding Low Power modes questions, please look at

i.MX6 Reference Manual and create (if necessary new Community threads).

i.MX6DQ Reference Manual (rev.1  4/2013)

http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf

Best regards

chip

[scottwalter]

Sorry for responding so late. I checked out your picture of your reference manual and I don't need to disable the PWM from a user's perspective, but from a developer's POV. On previous i.MX6 boards you could do this by toggling a pin via a register but I can't happen to find this pin. Also, strangely, page 288 of the updated reference manual for the i.MX6DQ is not this page at all. 

[igorpadykov]

Hi Scott

PWM module is the same (with minor

modifications) on all i.MX processors.

Best regards

chip

[scottwalter]

Ok, so there's a really handy method declared in the pwm_ifc.h and defined in the pwm.c driver that's a part of the iMX6DQ SDK for the PWM which disables and enables the pwm. This should be sufficient for disabling and enabling the monitor, I believe. I will do testing.