树莓派4直接上电，试过诸多参数，HDMI在我的显示器上（LG27M35）无法显示。
但是改电脑USB3.0供电，HDMI工作正常。
相关参数如下：
/boot/config.txt
# uncomment if hdmi display is not detected and composite is being output
hdmi_force_hotplug=1
# uncomment to force a specific HDMI mode (this will force VGA)
hdmi_group=1
hdmi_mode=16
# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
hdmi_drive=2
# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
config_hdmi_boost=4
