iMXRT1052 LCD Screen shifted

[jh1]

I observed an issue with a 1024x600 pixel LCD connected to an iMXRT1052. The problem is that the screen content is shifted by an arbitrary number of pixels. The screen content is loaded from an external NAND-Flash The result looks like this:

I found the solution here: 

Display is shifted when images are read from flash memory (directAccess project option set for bitma... 

It seems that the LCD controller had an underflow of data.

I could finally resolve the issue by changing the priority of the NIC-301 LCD-read_qos register from 1 to 11 (see Reference Manual 29.4) like this:

uint32_t* LCD_read_qos = (uint32_t*)0x41044100;
*LCD_read_qos = 11;

I find it curious that the default priority value is 1which is obviously not sufficient. 

I was wondering if anyone else had a similar issue?

[jh1 · Accepted solution]

Hi,

we figured out an additional important setting (thanks to the AN12302: i.MX RT eLCDIF RGB Mode Use Case: Chapter 4. eLCDIF demo and performance tuning):

ELCDIF_AXIMasterFeature(LCDIF, kELCDIF_AXI_burst_len_8 | kELCDIF_outstanding_req_8);

This sets the "LCDIF General Control2 Register" (see eLCDIF chapter in RM) and allows for using a lower priority value of 5 (instead of 11). 

Kind regards,

Johann

[victorjimenez]

Hello Johan, 

This behavior is specified in a comment of the SDK. It's up to each customer to modify this value according to their needs. Within the SDK we recommend that value doesn't be greater than 5. If you put 5 instead of 11, do you still face the shift behavior? 

Regards, 

Victor 

[jh1]

Hello Victor,

thx for your answer. Couldn't find this comment.

Well priority of 5 is not enough - i need a min. value of 11.

Kind regards,

Johann

[victorjimenez]

Hello Johann, 

Which version of the SDK are you using? Please download the newest version available (2.7). 

The comment is right above the code that you modified:  

Regards, 

Victor