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.

Esp WROOM32

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 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. In particular:

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

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 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:

  • BLE support
  • Touch detection support