RTC Connector
The Radxa ROCK 4D features an onboard RTC battery connector that allows you to connect an RTC battery. This provides continuous power to the Real-Time Clock (RTC) chip during power loss, ensuring the system clock continues to keep accurate time even when the board is powered off.
User Guide
To use the RTC connector, connect an RTC battery with the following specifications:
- Connector Type: 2-Pin XH 1.25mm
- Battery Type: CR2032
- Battery Voltage: 3.0V
Checking RTC Status
To verify if the system recognizes the RTC battery, run the following command in the terminal:
sudo dmesg | grep rtc
If the RTC battery is properly recognized, you should see output similar to rtc information is valid:
[ 8.145303] [drm] Esmart1-win0(possible_vp_mask = 0x00000006) has no possible crtcs
[ 8.145370] [drm] Esmart3-win0(possible_vp_mask = 0x00000006) has no possible crtcs
[ 8.153133] rockchip-drm display-subsystem: [drm] Cannot find any crtc or sizes
[ 8.154487] rockchip-drm display-subsystem: [drm] Cannot find any crtc or sizes
[ 8.700833] rtc-hym8563 2-0051: hym8563_init_device: error read i2c data -6
[ 8.716545] rtc-hym8563 2-0051: rtc information is valid
[ 8.724597] rtc-hym8563 2-0051: registered as rtc0
[ 8.725670] rtc-hym8563 2-0051: setting system clock to 2000-01-01T00:00:23 UTC (946684823)
Reading RTC Time
To read the current time from the RTC chip (/dev/rtc0), use the hwclock command:
sudo hwclock -r -f /dev/rtc0
Displaying System Time
To view the current system time, use the date command:
date
Setting RTC Time
If the RTC time doesn't match the system time, you can write the current system time to the RTC using:
sudo hwclock -w -f /dev/rtc0
Verifying RTC Functionality
To verify the RTC is working correctly:
- Note the current system time
- Disconnect power and network from the Radxa ROCK 4D
- Wait approximately 10 minutes
- Reconnect power and check if the system time has maintained accurate timekeeping
Interface Specifications
For detailed interface specifications, please refer to the Hardware Design: Schematics in the download section.
| Pin# | Name | Pin# | Name |
|---|---|---|---|
| 1 | OSCI | 5 | I2C2_SDA_M0_CC_RTC |
| 2 | OSCO | 6 | I2C2_SCL_M0_CC_RTC |
| 3 | RTC_INT_L | 7 | 32KOUT_RTC |
| 4 | GND | 8 | VCC_RTC |