PICO-IMX8M-MINI TEVS Camera Usage Guide

Introduction

This article guides you how to get started using TEVS Series camera on PICO-IMX8M-MINI.

Background knowledge needed

You must have the background knowledge to modify the kernel configuration, rebuild, and replace the kernel and the device tree source (DTS).

Supported Camera Modules

TEVI-OV5640 and TEVI-AR Series Cameras is no longer supported from Yocto 4.2

TEVI-OV5640 and TEVI-AR Series Cameras are only supported up to Yocto 4.0. If you want to use them, you can refer to Yocto 4.0 (Kirkstone) 2024Q1 Release.

Overview

• Connect debug console, power and camera to board

• Prepare Yocto demo image for testing TechNexion camera

• Build Yocto

• Instructions for testing camera

• Trouble shooting

Connect debug console, power and camera to board

1. Prepare DC 5V power cable to plug in. (Note: PICO-PI-8M is powered by USB Type C)

2. Prepare UART cable connect to debug console of PICO-PI-8M.

3. It's recommended to prepare a FPC cable to connect board will be more easy to use.

   

Prepare Yocto demo image for testing TechNexion camera

The demo image contains the required device tree blobs and camera drivers to enable TechNexion cameras.
Prebuilt demo images can be available for download via TechNexion's server.

Image Download Link:
Supported Release List

You can find the prebuilt images page in Release Notes, take YP4.2 2024Q3 for example:

Flash image to e.MMC

• Using 'uuu' to flash
  UUU

boot mode

Ensure the boot mode is configured as serial download mode.
Boot Configurations of PICO-PI-IMX8M-MINI

• Using u-boot's 'ums' Command to Write Flash Storage over USB-OTG
  UMS

u-boot

The board must also boot from either e.MMC with a version of U-boot that has the ums command enabled.

Please refer to Instructions for testing camera section for camera testing steps.

Build Yocto

Supported TechNexion Linux kernel branch for TEVS camera modules.

Fetch Yocto source
Build Yocto

Instructions for testing camera

Specify camera DTBO in u-boot

Auto detect camera

If you are using TEVS cameras, you can skip this section because it have auto detect camera function in u-boot.

1. Connect debug console cable to PICO-PI-IMX8M-MINI.

2. Power on board , and enter u-boot prompt.

3. Specify camera dtb via 'dtoverlay' u-boot environment variable.

   u-boot=> setenv dtoverlay tevs

4. Continue boot process.

   u-boot=> saveenv
   u-boot=> boot

Start camera video stream via gstreamer

Specify the capture device you just get and start gstreamer to get video stream on screen:

$ gst-launch-1.0 v4l2src device=/dev/video0 ! video/x-raw, width=<res_w>,height=<res_h> ! imxvideoconvert_g2d ! waylandsink window-width=<x> window-height=<y> sync=false

imxvideoconvert_g2d

It must have to use or using videoconvert. Because IMX8MM doesn't have ISI to convert format.

Trouble shooting

Ensure camera device tree blob overlay(DTBO) is specified correctly in u-boot.

u-boot=> printenv dtoverlay
dtoverlay=tevs

We can check whether camera have been initialized correctly.

$ dmesg -t | grep tevs
tevs 1-0048: tevs_probe() device node: tevs@48
tevs 1-0048: Version:24.9.0.1
tevs 1-0048: Product:TEVS-AR0144, HeaderVer:3, MIPI_Rate:800
tevs 1-0048: probe success