ESP-WROOM32¶

The ESP-WROOM32 developed by Espressif is based on the ESP32 microcontroller that boasts Wifi, Bluetooth, Ethernet and Low Power support all in a single chip.

Pin Mapping¶

The ESP-WROOM32 module is supported as a Zerynth customizable Virtual Machine, therefore the pinmap must be defined by the user. Please refer to here for more info on creating custom Virtual Machines.

Flash Layout¶

The internal flash of the ESP32 module is organized in a single flash area with pages of 4096 bytes each. The flash starts at address 0x00000, but many areas are reserved for Esp32 IDF SDK and Zerynth VM. There exist two different layouts based on the presence of BLE support.

In particular, for non-BLE VMs:

Start address	Size	Content
0x00009000	16Kb	Esp32 NVS area
0x0000D000	8Kb	Esp32 OTA data
0x0000F000	4Kb	Esp32 PHY data
0x00010000	1Mb	Zerynth VM
0x00110000	1Mb	Zerynth VM (FOTA)
0x00210000	512Kb	Zerynth Bytecode
0x00290000	512Kb	Zerynth Bytecode (FOTA)
0x00310000	512Kb	Free for user storage
0x00390000	448Kb	Reserved

For BLE VMs:

Start address	Size	Content
0x00009000	16Kb	Esp32 NVS area
0x0000D000	8Kb	Esp32 OTA data
0x0000F000	4Kb	Esp32 PHY data
0x00010000	1216Kb	Zerynth VM
0x00140000	1216Kb	Zerynth VM (FOTA)
0x00270000	320Kb	Zerynth Bytecode
0x002C0000	320Kb	Zerynth Bytecode (FOTA)
0x00310000	512Kb	Free for user storage
0x00390000	448Kb	Reserved

Device Summary¶

Microcontroller: Tensilica 32-bit Single-/Dual-core CPU Xtensa LX6
Operating Voltage: 3.3V
Input Voltage: 7-12V
Digital I/O Pins (DIO): 28
Analog Input Pins (ADC): 8
Analog Outputs Pins (DAC): 2
UARTs: 3
SPIs: 2
I2Cs: 3
Flash Memory: 4 MB
SRAM: 520 KB
Clock Speed: 240 Mhz
Wi-Fi: IEEE 802.11 b/g/n/e/i:
- Integrated TR switch, balun, LNA, power amplifier and matching network
- WEP or WPA/WPA2 authentication, or open networks

Connect, Register, Virtualize and Program¶

The workflow for custom Virtual Machines varies depending on the feature of the PCB hosting the module. Registration, virtualization and programming can be done both through an usb-to-serial converter linked to one of the serial port of the ESP-WROOM32 or through jtag.

Firmware Over the Air update (FOTA)¶

The Firmware Over the Air feature allows to update the device firmware at runtime. Zerynth FOTA in the ESP-WROOM32 device is available for bytecode and VM.

Flash Layout is shown in table below:

Start address	Size	Content
0x00010000	1Mb	Zerynth VM (slot 0)
0x00110000	1Mb	Zerynth VM (slot 1)
0x00210000	512Kb	Zerynth Bytecode (slot 0)
0x00290000	512Kb	Zerynth Bytecode (slot 1)

For BLE VMs:

Start address	Size	Content
0x00010000	1216Kb	Zerynth VM (slot 0)
0x00140000	1216Kb	Zerynth VM (slot 1)
0x00270000	320Kb	Zerynth Bytecode (slot 0)
0x002C0000	320Kb	Zerynth Bytecode (slot 1)

For Esp32 based devices, the FOTA process is implemented mostly by using the provided system calls in the IDF framework. The selection of the next VM to be run is therefore a duty of the Espressif bootloader; the bootloader however, does not provide a failsafe mechanism to revert to the previous VM in case the currently selected one fails to start. At the moment this lack of a safety feature can not be circumvented, unless by changing the bootloader. As soon as Espressif relases a new IDF with such feature, we will release updated VMs.

Secure Firmware¶

Secure Firmware feature allows to detect and recover from malfunctions and, when supported, to protect the running firmware (e.g. disabling the external access to flash or assigning protected RAM memory to critical parts of the system).

This feature is strongly platform dependent; more information at Secure Firmware - ESP32 section.

Missing features¶

Not all IDF features have been included in the Esp32 based VMs. In particular the following are missing but will be added in the near future:

Touch detection support