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Divine D. Rev. 1.1 Hardware Architecture

· 5 min read
Dr.-Ing. Sadok Bdiri
Dr.-Ing. Sadok Bdiri
CEO @ dawndrums

dd-rev1.1-arch

Hardware Architecture​

Divine D. continues its rapid evolution toward a stable, community-powered, open mobile system.

This article highlights all the new blocks, updated subsystems, and design decisions that distinguish Rev. 1.1 from Rev. 1.0. SecondPCB is deprecated and its features are now merged with mainPCB.

Overview of Rev. 1.1 Improvements​

Rev. 1.1 introduces several key subsystems that significantly improve connectivity, power management, audio routing, and expandability. These upgrades reflect community feedback and engineering validation. It also takes into consideration the design fixes and changes from the system evaluation of Rev 1.0

1. microSD Express (Spec 7.x)​

This represents a significant advancement in storage technology for open-source systems. The microSD Express now interfaces with PCIe 2.0 Gen 2 x1, enabling data transfer rates of up to 500 MB/s. One of the standout improvements is the markedly increased IOPS compared to legacy microSD and eMMC 5.1, enhancing overall system performance.

Following the SD specifications of 7.x, the hardware allows for multiplexing between legacy microSD (SDMMC) and microSD Express. Since the RK3588S does not natively support SDexpress, the operating system is required to manage an external de/multiplexer. This setup enables dynamic switching between interfaces based on user or system requirements, optimizing flexibility and efficiency.

2. Micro HDMI Display Output​

HDMI connector is added to allow connecting an external display and output an image resolution up to 7680x4320 or 8k @ 60Hz.

3. LoRa Subsystem​

One of the biggest additions in Rev. 1.1 is the integration of a LoRa transceiver, connected via UART

Why this matters

LoRa opens immersive experimentation possibilities:

  • Ultra-low-power long-range messaging
  • Off-grid peer-to-peer communication
  • Community mesh networks
  • IoT gateway scenarios

This gives Divine D. one of the most flexible wireless stacks seen in an open smartphone.

4. New Load and Battery Power Switches​

Rev. 1.1 introduces a 2 Load Switches between the PMIC and the charger and between the battery and the charger. The addition improves power path and control over the overall system power.

5. Haptic Engine Added​

A dedicated Haptic Engine block (motor + driver) now appears in Rev. 1.1.
Connected via I²C, it enables:

  • Vibrations
  • UI feedback
  • Alerts
  • Custom waveform control

6. Under-Voltage Battery Monitor​

To enhance the battery management system, we have integrated a battery voltage monitor that efficiently manages dead battery mode without requiring any interaction from the host system. This improvement was driven by several tests conducted on Rev. 1.0, which revealed that the charger failed to isolate the battery when its voltage dropped below 3V.

In such scenarios, the system encountered boot loops as it attempted to charge the battery while the load remained excessively high, particularly during the boot process. With the new UV (Under Voltage) battery monitor in place, the system's load switch automatically opens the circuit to disconnect the load until the battery voltage rises above a predefined threshold of 3.5V.

Additionally, the monitor incorporates a delay mechanism and hysteresis to ensure reliable operation, preventing unnecessary cycling and enhancing the overall efficiency of the charging process. These enhancements significantly improve the reliability and longevity of the device under varying battery conditions.

7. Battery Switch​

The battery can now be fully disconnected from the load via a bi-directional load switch. When this disconnection occurs, users still have the option to power on the system simply by connecting the charger. This allows also to override the UV battery monitor, allowing for operation even when the battery is disconnected or deeply discharged.

8. New LEDs​

New LED indicators were added:

  • RGB System LED (PMIC ON, User, Boot)
  • Charger LED (charging state)
  • Battery LED (UV battery monitor state)
  • LoRa status LED (LoRa connectivity state)
  • Drumhead LEDs (User)
  • Infrared LED (User)

These help during early firmware and software bring-up and user feedback.

9. Expanded Accessory Side Pogo Interface​

An 18-pin magnetic pogo interface implements:

  • UART/Debug
  • USB2
  • GPIOs
  • SPI
  • Muxed JTAG SWD for the SoC, Soc's MCU and LoRa
  • Bi-directional power path

This strengthens Divine D. as an experiment-friendly open hardware platform.

10. M.2 B-key GSM and 4G module​

The PCIe is not deprecated and replaced by an M.2 B-key to save more space on the assembly and also for a smaller connected module. An M.2 4230 can be fitted in.

11. Design fixes​

Based on the previous tests and runs, some design fixes and improvements have been added to the existing sub-systems. Most notable changes have been implemented on:

  • HiFi DAC
  • GNSS
  • DDR voltage rail on the PMIC
  • Component footprints
  • SPI Nor is deprecated

Summary of What's New in Rev. 1.1

SubsystemAdded or Updated
**microSD Express (Spec 7.x)Added microsSD express interface
**Micro HDMI Display OutputHDMI 2.1 connector with 8k @ 60Hz
LoRa ModuleNew long-range communication subsystem
Power SwitchesNew power domain isolation/control
Haptic EngineAdded motor + driver via I²C
UV Battery MonitorAdded under-voltage monitoring for the battery
Battery SwitchA slide switch to disconnect the battery
Indicator and IR LEDsNew indicator LEDs and IR LED
Pogo Accessory InterfaceInterface to accessory with GPIO/SPI/UART/I2C/JTAG mapping
M.2 B-key GSM and 4G InterfaceInterface to connect an M.2 B-key for GSM and 4G
Design fixesFixes from the last system evaluation

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