The ESP32 DevKitC is one of the development board created by Espressif to evaluate the ESP-WROOM-32 module. It is based on the ESP32 microcontroller that boasts Wifi, Bluetooth, Ethernet and Low Power support all in a single chip.
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. In particular:
|0x00009000||16Kb||Esp32 NVS area|
|0x0000D000||8Kb||Esp32 OTA data|
|0x0000F000||4Kb||Esp32 PHY data|
|0x00110000||1Mb||Zerynth VM (FOTA)|
|0x00290000||512Kb||Zerynth Bytecode (FOTA)|
|0x00310000||512Kb||Free for user storage|
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
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
Power to the Esp32 DevKitC is supplied via the on-board USB Micro B connector or directly via the “VIN” pin. The power source is selected automatically.
The device can operate on an external supply of 6 to 20 volts. If using more than 12V, the voltage regulator may overheat and damage the device. The recommended range is 7 to 12 volts.
Connect, Register, Virtualize and Program¶
The Esp32 DevKitC comes with a serial-to-usb chip on board that allows programming and opening the UART of the ESP32 module. Drivers may be needed depending on your system (Mac or Windows) and can be download from the official Espressif documentation page. In Linux systems, the DevKitC should work out of the box.
For Linux Platform: to allow the access to serial ports the user needs read/write access to the serial device file. Adding the user to the group, that owns this file, gives the required read/write access:
- Ubuntu distribution –> dialout group
- Arch Linux distribution –> uucp group
Once connected on a USB port, if drivers have been correctly installed, the DevKitC device is recognized by Zerynth Studio. The next steps are:
- Select the DevKitC on the Device Management Toolbar (disambiguate if necessary);
- Register the device by clicking the “Z” button from the Zerynth Studio;
- Create a Virtual Machine for the device by clicking the “Z” button for the second time;
- Virtualize the device by clicking the “Z” button for the third time.
No user intervention on the device is required for registration and virtualization process
After virtualization, the DevKitC is ready to be programmed and the Zerynth scripts uploaded. Just Select the virtualized device from the “Device Management Toolbar” and click the dedicated “upload” button of Zerynth Studio.
No user intervention on the device is required for the uplink process.
Firmware Over the Air update (FOTA)¶
The Firmware Over the Air feature allows to update the device firmware at runtime. Zerynth FOTA in the DevKitC device is available for bytecode and VM.
Flash Layout is shown in table below:
|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.
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
- Real time clock support
- Watchdog support (however, global watchdog is active by default)