Request for Guidance on Modifying Display Power Rail Voltages in GMT2194 PMIC for E Ink Panel on i.M

[Radhika_changela]

We are currently bringing up the E Ink paper display on the x-8ULP-ACEP-EPD board. We are using the GMT2194 PMIC to manage the display power subsystem. 

We need to modify the display power rail voltages to match the supported voltage range of the display. Specifically, the display requires -15V, but the PMIC is configured by default to output -17V. 

We are using the following: 

• Device Tree Source (DTS) file: imx8ulp-acep.dts 
• PMIC driver source: gmt2194-core.c 

Could you please guide us on how to change the PMIC regulator voltages accordingly? 

[Chong]

Hi @Radhika_changela ,

Can you provide all the voltage rail values ​​you require? 
I can help and  change it.

Best regards,
Chong

[Radhika_changela]

Hi @Chong ,

I am using the E Ink ED103TC2 E-Paper display, and the following power rail voltages are required for proper operation:

• VPOS3 = 28V

• VPOS2 = 15V

• VNEG3 = -20V

• VNEG2 = -15V

Best regards,
Radhika_changela

[Chong]

Hi @Radhika_changela ,

You can try the following settings in drivers/regulator/gmt2194-regulator.c

unsigned short VNEG1_HEX = 0x0514;
unsigned short VPOS1_HEX = 0x0514;
unsigned short VPOS2_HEX=0x69B
unsigned short VNEG2_HEX=0x69B
unsigned short VPOS3_HEX=0x389
unsigned short VNEG3_HEX=0x20C
unsigned short VCOM_HEX = 0x0948;

Best regards,
Chong

[Radhika_changela]

Hi @Chong 

Thank you for the support.

My PMIC generated required output voltages hex value in driver file.

Best regards,

Radhika_changela 

[JorgeCas]

Hello,

The G2194 PMIC board was designed by GMT and EINK please put in contact with them for further support.

Unfortunately, we do not have access to the source code. 

Best regards.

[Radhika_changela]

Hi,

Thanks for the update.

Is there any way to set this voltage through the device tree file?

As we don’t have direct contact with GMT, it would be great if you could help us with this.