This board definition covers not just a single board, but rather a large set of generic boards that use an ESP32-WROOM-32 module and simply break out all GPIOs to external pads without having any special hardware or interfaces on-board. Examples are Espressif's ESP32-DevKitC or NodeMCU-ESP32S and a large number of clones.
Most features of ESP32 boards are provided by the ESP32 SoC. The following table summarizes these features and gives an overview of which of these features are supported by RIOT. For detailed information about the ESP32, see section \ref esp32_mcu "MCU ESP32".
<center>
MCU | ESP32 | Supported by RIOT
------------|-----------|------------------
Vendor | Espressif | |
Cores | 1 or 2 x Tensilica Xtensa LX6 | 1 core
FPU | yes (ULP - Ultra low power co-processor) | no
Generic ESP32-WROOM-32 boards do not have special hardware on board and all GPIOs are simply broken out for flexibility. Therefore, the board configuration is the most flexible one with provides:
18 x ADC channels at maximum
2 x DAC channels at maximum
2 x SPI at maximum
1 x I2C at maximum
2 x UART
Since all GPIOs have broken out, GPIOs can be used for different purposes in different applications. For flexibility, GPIOs can be listed in various peripheral configurations. For example, GPIO13 is used in the ADC channel definition and the definition of the MOSI signal of SPI_DEV(0).
This is possible because GPIOs are only used for a specific peripheral interface when
- the corresponding peripheral module is used, eg. periph_i2c, or
- a corresponding init function is called z. adc_init, dac_init and pwm_init or
- The corresponding peripheral interface is used for the first time, eg. spi_aqcuire.
That is, the purpose for which a GPIO is used depends on which module or function is used first.
For example, if module periph_i2c is not used, the GPIOs listed in I2C configuration can be used for the other purposes.
The following table shows the default board configuration, which is sorted according to the defined functionality of GPIOs. This configuration can be overridden by \ref esp32_app_spec_conf "application-specific configurations".
MRF24J40-based IEEE 802.15.4 radio modules and ENC28J60-based Ethernet network interface modules have been tested with the board. You could use the following code in your \ref esp32_app_spec_conf "application-specific configuration" to use such modules:
```
#ifdef BOARD_ESP32_WROOM-32
#if MODULE_MRF24J40
#define MRF24J40_PARAM_CS GPIO16 /* MRF24J40 CS signal */
#define MRF24J40_PARAM_RESET GPIO17 /* MRF24J40 RESET signal */
#define MRF24J40_PARAM_INT GPIO34 /* MRF24J40 INT signal */
#endif
#if MODULE_ENC28J80
#define ENC28J80_PARAM_CS GPIO32 /* ENC28J80 CS signal */
#define ENC28J80_PARAM_RESET GPIO33 /* ENC28J80 RESET signal */
#define ENC28J80_PARAM_INT GPIO35 /* ENC28J80 INT signal */
For other parameters, the default values defined by the drivers can be used.
@note The **RESET** signal of MRF24J40 and ENC28J60 based modules can also be connected to the **RST** pin of the board (see \ref esp32_wroom_32_pinout "pinout") to keep the configured GPIO free for other purposes.
The following figure shows the pinout of the defined default configuration for the EPS32-DevKitC board as an example of generic ESP32-WROOM-32 boards. The light green GPIOs are not used by configured on-board hardware components and can be used for any purpose. However, if optional off-board hardware modules are used, these GPIOs may also be occupied, see \ref esp32_wroom_32_table_board_configuration "optional functions" in table board configuration.
The corresponding board schematics can be found her [here](https://dl.espressif.com/dl/schematics/esp32_devkitc_v4-sch-20180607a.pdf)
\anchor esp32_wroom_32_pinout
@image html "https://gitlab.com/gschorcht/RIOT.wiki-Images/raw/master/esp32/ESP32-WROOM-32_pinouts.png?inline=false" "EPS32-DevKitC V4 Pinout"
## <a name="flashing"> Flashing the Device </a> [[TOC](#toc)]
Flashing RIOT is quite easy. The board has a Micro-USB connector with reset/boot/flash logic. Just connect the board to your host computer and type using the programming port:
```
make flash BOARD=esp32-wroom-32 ...
```
For detailed information about ESP32 as well as configuring and compiling RIOT for ESP32 boards, see \ref esp32_riot.
