DS90UB941AS-Q1: External Reference Clock Mode

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Part Number: DS90UB941AS-Q1
Other Parts Discussed in Thread: LMK3H0102-Q1, , LMK3H0102

We want to try to use External Reference Clock Mode mode to light up the display on the DS90UB941 (the Ref Clk clock source comes from OUTPUT0 of the LMK3H0102-Q1 chip). What registers do we need to configure? The External DSI Clock and Ext timing we are currently using. I tried to add 0x56 to write 0x01 based on the following configuration. I don’t know if the configuration timing is incorrect, so the screen is black.

119  static struct dsi_panel_param dsi_panel_parameter[] = {
120  	//15inch
121  	{
122  	.t_clk_post = 0x0e,
123  	.t_clk_pre = 0x1e,
124  	.h_active = 2240,
125  	.v_active = 1260,
126  	.h_front_porch = 24,
127  	.h_back_porch = 40,
128  	.h_sync_width = 28,
129  	.v_front_porch = 6,
130  	.v_back_porch = 4,
131  	.v_sync_width = 2,
132  	},

dsi clock = v total * h total * fps = (1260+6+4+2) * (2240+24+40+28) * 60 = 177,978,240 HZ


Our current DS90UB941 configuration is as follows. How to add the ref clk mode on this basis

writeLvdsRegister(0x01,0x08);

writeLvdsRegister(0x40,0x04);

writeLvdsRegister(0x41,0x05);

writeLvdsRegister(0x42,0x3C); //DPHY_SKIP_TIMING

writeLvdsRegister(0x41,0x21); //DSI_CONFIG_1

//DSI_VS_POLARITY:1->VS signal is active low;DSI_HS_POLARITY:1->HS signal is active low;DSI_NO_EOTPKT:1

writeLvdsRegister(0x42,(1<<6)|(1<<5)|(1<<0));

writeLvdsRegister(0x01,0x00);

2 个月前

0 Taylor 2 个月前

TI__Mastermind 34395 points

您好，

已经收到了您的案例，调查需要些时间，感谢您的耐心等待。

0 Alice 2 个月前回复 Taylor

TI__Mastermind 35760 points

您好，

请参考DS90UB941AS-Q1 DSI Bringup Guide

请使用“"Figure 3-2. Recommended DS90UB941AS-Q1 Bring-Up Flow" ”配置，并使用PatGen进行测试验证。

请注意DSI clock frequency = ((pixel clock rate) * bits per pixel) / (2 * number of DSI lanes)

下面脚本请参考

## Pixel Clock = 148.5 MHz (eg. for standard 1080p)
## DSI clock = 445.5 MHz

## DSI input port 0
## 4 lanes DSI

 
import time

serAddr = 0x18
desAddr0 = 0x58

#RESET 941
board.WriteI2C(serAddr,0x01,0x02)

#Disable DSI
board.WriteI2C(serAddr,0x01,0x08)

board.WriteI2C(serAddr,0x1E,0x01) # Select DSI0
board.WriteI2C(serAddr,0x4F,0x8C) # Set single DSI0 mode - continuous clock mode

board.WriteI2C(serAddr,0x40,0x04) # TSKIP_CNT DSI0
board.WriteI2C(serAddr,0x41,0x05) # TSKIP_CNT DSI0
board.WriteI2C(serAddr,0x42,0x30) # TSKIP_CNT DSI0, TSKIP_CNT (dec)= 24


board.WriteI2C(serAddr,0x40,0x04) # Set HSYNC/VSYNC Polarity DSI0
board.WriteI2C(serAddr,0x41,0x21) # Set HSYNC/VSYNC Polarity DSI0
board.WriteI2C(serAddr,0x42,0x60) # Set HSYNC/VSYNC Polarity DSI0


board.WriteI2C(serAddr,0x40,0x10) # Init DSI Clock Settings (From Section 10.2 of datasheet)
board.WriteI2C(serAddr,0x41,0x86) # Init DSI Clock Settings (From Section 10.2 of datasheet)
board.WriteI2C(serAddr,0x42,0x0A) # Init DSI Clock Settings (From Section 10.2 of datasheet)
board.WriteI2C(serAddr,0x41,0x94) # Init DSI Clock Settings (From Section 10.2 of datasheet)
board.WriteI2C(serAddr,0x42,0x0A) # Init DSI Clock Settings (From Section 10.2 of datasheet)

#Enable DSI
board.WriteI2C(serAddr,0x01,0x00)

0 ?? ? 2 个月前回复 Alice

Prodigy 10 points

好的，感谢您的回复支持，但是我没看到bringup flow中有关于externel ref clk的配置方法和案例，还请帮忙看下如果要配置external ref clk应该配置哪些寄存器，在上电时序中的什么时机配置。

0 ?? ? 2 个月前回复 ?? ?

Prodigy 10 points

Hello TI:

如下是我们的配置，使用的external ref clk和internal timing，验证下来黑屏，如果去掉external ref clk则显示彩虹条

writeLvdsRegister(0x01,0x08);
writeLvdsRegister(0x40,0x04);
writeLvdsRegister(0x41,0x05);
writeLvdsRegister(0x42,0x3c); //DPHY_SKIP_TIMING

writeLvdsRegister(0x41,0x21); //DSI_CONFIG_1
//DSI_VS_POLARITY:1->VS signal is active low;DSI_HS_POLARITY:1->HS signal is active low;DSI_NO_EOTPKT:1
writeLvdsRegister(0x42,(1<<6)|(1<<5)|(1<<0));

#if USE_DS90UB948_Q1
writeLvdsRegister(0x1E,0x01);
writeLvdsRegister(0x1E,0x04);
writeLvdsRegister(0x1E,0x01);
writeLvdsRegister(0x03,0x9A); //I2C Pass-Through enable
#endif
#if USE_PATTERN_MODE
writeLvdsRegister(0x1E,0x01); //Selects Port 0

writeLvdsRegister(0x66,0x04);
writeLvdsRegister(0x67,0x36); //Total Horizontal Width: 0~7

writeLvdsRegister(0x66,0x05);
writeLvdsRegister(0x67,0x09|(0x0A<<4)); //Total Horizontal Width: 11~8 |Total Vertical Width:3~0|

writeLvdsRegister(0x66,0x06);
writeLvdsRegister(0x67,0x4F); //Total Vertical Width: 11~4

writeLvdsRegister(0x66,0x07);
writeLvdsRegister(0x67,0xC0); //Active Horizontal Width: 0~7

writeLvdsRegister(0x66,0x08);
writeLvdsRegister(0x67,0x08|(0x0C<<4)); //Active Horizontal Width: 11~8 |Active Vertical Width:3~0|

writeLvdsRegister(0x66,0x09);
writeLvdsRegister(0x67,0x4E); //Active Vertical Width: 11~4

writeLvdsRegister(0x66,0x0A);
writeLvdsRegister(0x67,26); //Horizontal Sync Width:
writeLvdsRegister(0x66,0x0B);
writeLvdsRegister(0x67,2); //Vertical Sync Width:

writeLvdsRegister(0x66,0x0C);
writeLvdsRegister(0x67,68); //Horizontal Back Porch Width
writeLvdsRegister(0x66,0x0D);
writeLvdsRegister(0x67,6); //Vertical Back Porch Width

//Set Sync Polarities
writeLvdsRegister(0x66,0x0E);
writeLvdsRegister(0x67,1<<1|1<<0);

writeLvdsRegister(0x66,0x0F);
writeLvdsRegister(0x67,60);

writeLvdsRegister(0x66,0x03);
writeLvdsRegister(0x67,8);
writeLvdsRegister(0x66,0x1A);
writeLvdsRegister(0x67,2);

writeLvdsRegister(0x64,1<<2|1<<0); //Enable Color Bars Enable Pattern Generator
writeLvdsRegister(0x65,1<<2|1<<3); //internal timing

writeLvdsRegister(0x56,0x01); //enable 941 ref clk
writeLvdsRegister(0x4F,1<<7);
#endif
writeLvdsRegister(0x01,0x00);

external ref clk的时钟源为lmk3h0102芯片稳定的177.978Mhz，请问是否需要配置writeLvdsRegister(0x4F,1<<7); 连续时钟，另外当去掉writeLvdsRegister(0x56,0x01); //enable 941 ref clk后显示正常，请问这个ref clk配置应该放在哪里

当我去除

0 Alice 2 个月前回复 ?? ?

TI__Mastermind 35760 points

您好，

是的，您应该将寄存器 0x56[1:0] 设置为 0x1，以启用外部 REFCLK 模式。

如果是连续时钟模式，则还需要设置 0x4F[7]。请确保先读取 0x4F，以免错误覆盖位 0-6，例如 DSI 通道计数和其他位。

这些应在启用 DSI 之前以及在启用 DES 输出之前设置。因此，脚本中的设置是可以的。

0 ?? ? 2 个月前回复 Alice

Prodigy 10 points

脚本中的设置验证下来还是黑屏，无显示画面，还请帮忙分析排查下，谢谢

0 Alice 2 个月前回复 ?? ?

TI__Mastermind 35760 points

您好，

请检查是否存在硬件设计问题。

0 ?? ? 2 个月前回复 Alice

Prodigy 10 points

没有，目前量取的LMK3H0102的CLK直连941的ref clk，然后不使用941 ref clk使用dsi clk是能正常显示的，感觉还是941的ref clk配置不正确或者未生效，您能帮忙找下941使用ref clk的参考案例吗

0 ?? ? 2 个月前回复 ?? ?

Prodigy 10 points

不使用941 ref clk的时候显示画面正常，对应的寄存器表现如下：

使用941 ref clk的时候显示黑屏，对应寄存器表现如下：

请问如果使用external ref clk，LMK3H0102类似的时钟给过来的clk，这样941芯片的寄存器能detect到valid clk吗，这种非dsi clk的941寄存器看检测不到clk，请问还有什么办法能指导下吗

writeLvdsRegister(0x01,0x08);
writeLvdsRegister(0x40,0x04);
writeLvdsRegister(0x41,0x05);
writeLvdsRegister(0x42,m_SkipTiming); //DPHY_SKIP_TIMING
if(m_DisplayType == tuam::Def_Config_DisplayManagerConfiguration_abtDisplayType::eAbt15_0_2240x1260)
{
writeLvdsRegister(0x41,0x21); //DSI_CONFIG_1
//DSI_VS_POLARITY:1->VS signal is active low;DSI_HS_POLARITY:1->HS signal is active low;DSI_NO_EOTPKT:1
writeLvdsRegister(0x42,(1<<6)|(1<<5)|(1<<0));
}