USB HDMI Adapter

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This USB HDMI adapter board is specifically designed for the Raspberry Pi 5. Its primary function is to reposition the USB and HDMI connections to align with the USB interface side of the Raspberry Pi, enhancing accessibility and cable management.

Additionally, the HDMI port is converted to a standard HDMI Type A interface, offering broader compatibility.

A 1220RTC battery holder is incorporated for convenient installation of an RTC battery. It connects to the Raspberry Pi’s RTC interface via an SH1.0 2P reverse cable. The battery holder is compatible with both CR1220 and ML1220 batteries. If using an ML1220 (Lithium Manganese Dioxide battery), charging can be configured directly on the Raspberry Pi. Note that the CR1220 is not rechargeable.

Enabling Trickle Charging

By default, the trickle charging feature for the battery is disabled. The sysfs files indicate the current trickle charging voltage and limits:

pi@raspberrypi:~ $ cat /sys/devices/platform/soc/soc:rpi_rtc/rtc/rtc0/charging_voltage
0
pi@raspberrypi:~ $ cat /sys/devices/platform/soc/soc:rpi_rtc/rtc/rtc0/charging_voltage_max
4400000
pi@raspberrypi:~ $ cat /sys/devices/platform/soc/soc:rpi_rtc/rtc/rtc0/charging_voltage_min
1300000

To enable trickle charging, add rtc_bbat_vchg to /boot/firmware/config.txt:

  • Open the /boot/firmware/config.txt.

    sudo nano /boot/firmware/config.txt

  • Add rtc_bbat_vchg to /boot/firmware/config.txt.

    dtparam=rtc_bbat_vchg=3000000

After rebooting, the system will display:

pi@raspberrypi:~ $ cat /sys/devices/platform/soc/soc:rpi_rtc/rtc/rtc0/charging_voltage
3000000
pi@raspberrypi:~ $ cat /sys/devices/platform/soc/soc:rpi_rtc/rtc/rtc0/charging_voltage_max
4400000
pi@raspberrypi:~ $ cat /sys/devices/platform/soc/soc:rpi_rtc/rtc/rtc0/charging_voltage_min
1300000

This confirms the battery is now under trickle charging. To disable this feature, simply remove the dtparam line from config.txt.