The RedBear Duo supports running Particle firmware based applications and WICED SDK based applications. It is installed the customed Particle firmware by default during manufacturing. The following diagram exactly shows you the memory mapping on the Duo, comparing to the Particle Photon development board.
Important Note: Since the system firmware v0.3.0, the firmware architecture has been changed. The system firmware version below v0.3.0 will no longer be supported.
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Memory map since system firmware v0.3.0:
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Memory map till system firmware v0.2.4:
The Duo's memory allocation is different from the Photon. The Duo has an external flash while the Photon does not. The external flash stores the WiFi firmware to be loaded to the BCM43438 wirless chip during boot-up as well as other recovery firmware. Thus, this design allows the entire internal flash memory space of 256KB to be available for the user sketch.
The bootloader ranges from internal flash address 0x08000000 to 0x08007FFFF, the size of which is 32 KB. The bootloader is versatile. It determines whether to run the Particle firmware or WICED applications. If neither of them are valid, then it enters DFU mode for firmware uploading.
Besides, if the Duo is running Particle firmware, the bootloader is responsible for the factory application reset, applying the OTA downloaded firmware or user application, making the Duo enter Safe mode, clearing Wi-Fi credentials and etc.
The DCT (Device Configuration Table) ranges from internal flash address 0x08008000 to 0x0800FFFF, the size of which is 32 KB. It is separated into two partitions (DCT1 and DCT2) and each size is 16K. Only one of the DCTs is valid at a time and the another one is standby for swapping data. They are used alternately to keep the data integrate, in case of power down during changing the device configuration.
The DCT consists of two partitions:
- The Platform DCT, starting from the begining address of DCT1 or DCT2. Details...
- The Application DCT immediately following the Platform DCT.
Regarding to the Particle firmware architecture, the configurations in Application DCT are listed below. For more details, see here.
Region Offset Size
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system flags 0 32
version 32 2
device private key 34 1216
device public key 1250 384
ip config 1634 128
country code 1758 4
claim code 1762 63
claimed 1825 1
ssid prefix 1826 26
device id 1852 6
version string 1858 32
dns resolve 1890 128
reserved1 2018 64
server public key 2082 768
padding 2850 2
flash modules 2852 100
product store 2952 24
antenna selection 2976 1
cloud transport 2977 1
alt device public key 2978 128
alt device private key 3106 192
alt server public key 3298 192
alt server address 3490 128
reserved2 3618 640
extra system flags 4258 32
end 4290
Note: Particle Firmware architecture only
The EEPROM emulation is used to store user's non-volatile data, the size of which is 32 KB. It ranges from external serial flash address 0x000B8000 to 0x000BFFFF. The working mechanism of the EEPROM emulation is the same as DCT, it is separated into two partitions and only one is valid at a time:
- EEPROM emulation bank 1, 16 KB
- EEPROM emulation bank 2, 16 KB
See the EEPROM Emulation APIs.
Note: Particle Firmware architecture only
System part 1 ranges from internal flash address 0x08020000 to 0x0803FFFF, the size of which is up to 128 KB. It is part of the Particle system firmware, which implements the cloud communication and services functions. These functions can be invoked by system part 2 and user application, so they are so called "dynalibs" (dynamic libraries).
Note: Particle Firmware architecture only
System part 2 ranges from internal flash address 0x08040000 to 0x080BFFFF, the size of which is up to 512 KB. It is the mayor part of the Particle system firmware, which implements all of the Hardware Abstract Layer functions, including internal peripherals, WiFi, BLE and etc. They can be invoked by user application in the way of dynalibs.
The system part 2 is the core of the Particle firmware. It initialises the platform and runs the FreeRTOS real-time operating system. It is responsible for dealing with system events, OTA updating firmware and user application, configuring Wi-Fi credentials and calling the setup() and loop() functions in the user application.
The partition 2 firmware has a copy of bootloader, if it found the bootloader version is lower than the copy, then it will update the bootloader automatically.
The user part is the user application.
Regarding to the user application based on Particle firmware, it ranges from the internal flash address 0x080C0000 to 0x080FFFFF, the size of which is up to 256 KB. It is made up of the setup() and loop() functions, the same as the Arduino sketch.
Regarding to the user application based on WICED SDK, it ranges from the internal flash address 0x0800C000 to 0x080FFFFF, the size of which is up to 976 KB.
Note: Particle Firmware architecture only
The OTA Image ranges from external flash address 0xC0000 to 0x13FFFF, the size of which is up to 512 KB. It is the OTA downloaded system firmware or user application. The OTA downloaded images will be applied to internal flash during the next boot up.
Note: Particle Firmware architecture only
The Factory Reset image (FAC) ranges from external flash address 0x140000 to 0x17FFFF, the size of which is up to 256 KB. It should be a validated user application so that even if you have loaded a bad user application to internal flash, you can simply copy the factory reset image to where the user application locates by performing a factory reset action.
Note: Particle Firmware architecture only
The Wi-Fi firmware ranges from external flash address 0x180000 to the end of the external flash, the size of which is up to 512 KB. It will be loaded to the BCM43438 wireless chip in system part 2 during initialization.
Note: Particle Firmware architecture only
The user data region ranges from external flash address 0x0 to 0xB7FFF, the size of which is up to 736 KB. It is also used to store user's non-volatile data.
See the External SPI Flash APIs.
Note: WICED architecture only
This region is to store the WICED application relevant data, e.g the factory reset application, Wi-Fi firmware and etc.
- Getting Started with Arduino IDE
- Getting Started with Particle Build (Web IDE)
- Firmware Deployment Guide
- Arduino/C/C++ Programming Reference Manual
- JavaScript Programming Reference Manual
- Python Programming Reference Manual
- How It Works
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