Due to the release of i.MX8M, its corresponding development board circuit is designed with a USB type-c interface.

But some customers only need USB 2.0, not USB 3.0, or even USB type-c.

In order to enable customers with similar needs to successfully complete the design, this article will teach everyone how to design the "USB 2.0" schematic.

i. MX8MQ supports USB 3.0 and is compatible with USB 2.0. On the development board, use USB type-c design solution.

Therefore, we must remove the USB type-c, PD (power delivery) chip, and CC logic chip. At the same time, change the connection interface to micro USB and USB type-a.

Hardware design:

一、Firstly, gain a deeper understanding of the iMX8M's IOMUX list (USB related signals), as follows

二、circuit design

A、The design of USB power supply (USBV) and current protection (Over Current) is as follows

B、The design of the USB 1 interface (micro USB) is as follows

Usb1 is configured in dual role mode (HOST/Device), USB1_ OTG_ ID for detection

C、The design of the USB type-a interface is as follows

USB2 is configured as HOST role mode, USB2_ OTG_ ID for detection (grounding)

Supplementary information about USBx_ OTG_ ID and USBx_ Description of ID

(1) USBx_ OTG_ ID

USBx_ OTG_ ID, also known as GPIO_ ID. During the working process, the software changes the role between the device and host based on the level of the ID pin from high to low or from low to high.

(2) USBx_ ID

USBx_ The ID is called USB PHY ID and can also be executed in conjunction with USBx_ OTG_ Functions with the same ID.

(3) Using USBx_ OTG_ ID or USBx_ ID

Suggest using USBx_ OTG_ ID. However, if the customer wants to convert USBx_ If the ID is used for i.MX8MQ, it can be configured through USB_ CTL0_ ADDR [utmiotg_iddig_sel] register

Software adaptation:

一、IOMUX

According to practical applications, the signals to be used are multiplexed in dts files. This step is relatively simple and will not be repeated here.

二、Adjust the usb configuration in the u-boot/Device tree

Customers can delete imx8mm_ Evk_ Config in defconfi_ USB_ TCPC and removing typec from fsl-imx8mm-evk.dts_ Ptn5110_ 1/2 dependencies to try.

(Uboot does check the status of USB type-c, and if they are removed, they will crash or get stuck.)

--u-bootCONFIG_USB_TCPC=n--Node of Device tree&usb_dwc3_0 { status = "okay"; /*extcon = <&typec_ptn5100>;*/ dr_mode = "otg"; hnp-disable; srp-disable; adp-disable; maximum-speed = "high-speed";};

Above, users need to follow every step, that is, they can design the USB 2.0 interface on the i.MX8M platform without retaining the USB type c interface.

Source: Da Da Da Tong