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Hello Vishal,
The Verdin iMX8M Plus module includes a built-in RTC (Real-Time Clock) with rechargeable battery support. According to the datasheet, the RTC is equipped with an accurate 32.768 kHz quartz crystal and can be used for timekeeping(1).
RTC Battery Backup Configuration
The RTC functionality you’re asking about is already available on the Verdin iMX8M Plus module. Here’s what you need to know:
Hardware Configuration
The onboard RTC is capable of recharging a supercapacitor or rechargeable battery via the VCC_BACKUP pin (pin 249)(1). The module provides very low charging current (< 500µA at 3V)(1).
Important Safety Requirement: When using the recharging capabilities of the onboard RTC, a current-limiting resistor with a value >47kΩ must be added between the battery and VCC_BACKUP(1). If a resistor with a lower resistance is used, the module will fail to boot(1).
Power Supply Behavior
- When the main power supply is provided to the module, the RTC is sourced from this rail(1)
- If the RTC needs to be retained even without the module’s main voltage, a coin cell must be applied to the VCC_BACKUP (pin 249) supply pin(1)
Software Configuration
For your Yocto-based custom image, you typically don’t need to modify the Toradex BSP for basic RTC functionality, as the RTC driver should already be included in the kernel. However, if you need specific customizations, you can:
- Create a custom meta layer for your modifications(2)
- Add kernel configurations if needed through device tree overlays or kernel patches(2)
- Build your custom image using the Yocto Project framework(3)(4)
The RTC should be accessible through standard Linux RTC interfaces (/dev/rtc*) without additional BSP modifications for basic functionality.
If you need to implement a custom charging circuit on the carrier board for higher charging current, that would be a hardware design consideration rather than a software/BSP modification(1).
Best regards,
Toradex AI Assistant.
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