Linux/AM4379: LCD_CLK waveform issue

user5348122

Intellectual 270 points

Part Number: AM4379

Tool/software: Linux的

Normal should be square wave

Need to modify the software or hardware

How can I set it up?

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

Hi,

I cannot see the LCD clock frequency from your screenshot, but what I see is that you are using a 300MHz oscilloscope. Try to find an oscilloscope with higher bandwidth and you will see the signal properly.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

thank you very much

LCD_CLK High level requires 3.3v
How can I set it up?

0 Biser Gatchev-XID over 6 years ago in reply to user5348122

TI__Guru**** 393215 points

I/O voltage is defined from the VDDSHVx voltage rail that supplies the I/O pin.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

Need to modify the software or hardware, what should I do?

0 Biser Gatchev-XID over 6 years ago in reply to user5348122

TI__Guru**** 393215 points

Look at Table 4-10 from the AM437x Datasheet Rev. E. The LCD clock is named DSS_PCLK and is available on pin A22. This pin is powered from VDDSHV6. If VDDSHV6 is tied to a 3.3V power supply then DSS_PCLK high level will be 3.3V. This is entirely a hardware connection and cannot be changed by software.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

thank you very much

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

VDDSHV6 is tied to a 3.3V power supply. but
DSS_PCLK Set as 5MHZ ， High level is 3.4v.
DSS_PCLK Set as 30MHZ ， High level is 2.1v.
What is the reason？

0 Biser Gatchev-XID over 6 years ago in reply to user5348122

TI__Guru**** 393215 points

Please post the DSS part of the schematic, both on processor side and on display side.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

0 Biser Gatchev-XID over 6 years ago in reply to user5348122

TI__Guru**** 393215 points

This part seems OK. I see no reason why you should observe these levels on the LCD clock, except if you are still using the oscilloscope from the first screenshot you posted. This tool's bandwidth is too narrow to see a true square wave signal at these frequencies.

0 Biser Gatchev-XID over 6 years ago in reply to Biser Gatchev-XID

TI__Guru**** 393215 points

Another thing I notice is that your connections on CON14 do not match the connections on the LCD drawing. Please check.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

That's it, still using that oscilloscope

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

am4379 Support for 480*854 lcd screen?
Do you need to modify the kernel to use this screen?

0 user5348122 over 6 years ago

Intellectual 270 points

Part Number: AM4379

Tool/software: Linux

am4379 Add 480 × 854 LCD display panel, need to modify the kernel which code?

lcd0: display {
compatible = "osddisplays,osd057T0559-34ts", "panel-dpi";
label = "lcd";

panel-timing {
clock-frequency = <33000000>;
hactive = <480>;
vactive = <854>;
hfront-porch = <100>;
hback-porch = <50>;
hsync-len = <10>;
vback-porch = <16>;
vfront-porch = <20>;
vsync-len = <4>;
hsync-active = <0>;
vsync-active = <0>;
de-active = <1>;
pixelclk-active = <1>;
};

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

Hello, can you help me solve the problem behind me?

0 Biser Gatchev-XID over 6 years ago in reply to user5348122

TI__Guru**** 393215 points

This has been forwarded to the Linux team. They will post directly here as soon as possible.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

thank you very much! This problem has been bothering me for a week.

0 user5348122 over 6 years ago in reply to Biser Gatchev-XID

Intellectual 270 points

Hello, the Linux team has not responded yet?

I am very anxious now, I don't know what to do.

0 Manisha Agrawal over 6 years ago in reply to user5348122

TI__Mastermind 22946 points

Hi, You don't need to modify DSS driver to use your LCD panel. dts file configuration should be good enough, unless you have special configuration need for your LCD panel for which you need to write the panel driver.

What's the display behavior you are seeing with current dts settings?

Regards,
Manisha

0 user5348122 over 6 years ago in reply to Manisha Agrawal

Intellectual 270 points

No display

0 Manisha Agrawal over 6 years ago in reply to user5348122

TI__Mastermind 22946 points

What's meant by no display? The screen is black or improper output? Have you verified the pixels are toggling at the display panel input side as well on the DSS outpins?

What log do you see when you run the modetest application?

All the settings you did from dts file are sufficient configuration for your panel to work or something more needed?

Regards,

Manisha

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Linux/AM4379: LCD_CLK waveform issue