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RIOT/cpu/esp32/doc_esp32.txt
Gunar Schorcht 2ab2c13cb8 cpu/esp32: documentation fix
2023-07-07 11:12:01 +02:00

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/*
* Copyright (C) 2022 Gunar Schorcht
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
@defgroup cpu_esp32_esp32 ESP32 family
@ingroup cpu_esp32
@brief Specific properties of ESP32 variant (family)
@author Gunar Schorcht <gunar@schorcht.net>
\section esp32_riot_esp32 Specific properties of ESP32 variant (family)
## GPIO pins {#esp32_gpio_pins_esp32}
ESP32 has 34 GPIO pins, where only a subset can be used as output, as
ADC channel, as DAC channel and as GPIOs in deep-sleep mode, the so-called
RTC GPIOs. Some of them are used by special SoC components, e.g., as touch
sensors. The following table gives a short overview.
<center>
Pin | Type | ADC / RTC | PU / PD | Special function | Remarks
-------|:-------|:---------:|:---------:|-----------------------|--------
GPIO0 | In/Out | yes | yes | Touch sensor | Bootstrapping, pulled up
GPIO1 | In/Out | - | yes | UART0 TxD | Console
GPIO2 | In/Out | yes | yes | Touch sensor | Bootstrapping, pulled down
GPIO3 | In/Out | - | yes | UART0 RxD | Console
GPIO4 | In/Out | yes | yes | Touch sensor | -
GPIO5 | In/Out | - | yes | - | -
GPIO6 | In/Out | - | yes | Flash SD_CLK | -
GPIO7 | In/Out | - | yes | Flash SD_DATA0 | -
GPIO8 | In/Out | - | yes | Flash SD_DATA1 | -
GPIO9 | In/Out | - | yes | Flash SD_DATA2 | only in `qout`and `qio`mode, see section [Flash Modes](#esp32_flash_modes)
GPIO10 | In/Out | - | yes | Flash SD_DATA3 | only in `qout`and `qio`mode, see section [Flash Modes](#esp32_flash_modes)
GPIO11 | In/Out | - | yes | Flash SD_CMD | -
GPIO12 | In/Out | yes | yes | MTDI / Touch sensor | JTAG interface / Bootstrapping, pulled down
GPIO13 | In/Out | yes | yes | MTCK / Touch sensor | JTAG interface
GPIO14 | In/Out | yes | yes | MTMS / Touch sensor | JTAG interface
GPIO15 | In/Out | yes | yes | MTDO / Touch sensor | JTAG interface / Bootstrapping, pulled up
GPIO16 | In/Out | - | yes | - | usually not available when SPI RAM is used
GPIO17 | In/Out | - | yes | - | usually not available when SPI RAM is used
GPIO18 | In/Out | - | yes | - | -
GPIO19 | In/Out | - | yes | - | -
GPIO21 | In/Out | - | yes | - | -
GPIO22 | In/Out | - | yes | - | -
GPIO23 | In/Out | - | yes | - | -
GPIO25 | In/Out | yes | yes | DAC1 | -
GPIO26 | In/Out | yes | yes | DAC2 | -
GPIO27 | In/Out | yes | yes | Touch sensor | -
GPIO32 | In/Out | yes | yes | XTAL32_P | can be used to connect an external 32 kHz crystal
GPIO33 | In/Out | yes | - | XTAL32_N | can be used to connect an external 32 kHz crystal
GPIO34 | In | yes | - | VDET | -
GPIO35 | In | yes | - | VDET | -
GPIO36 | In | yes | - | SENSOR_VP | -
GPIO37 | In | yes | - | SENSOR_CAPP | usually not broken out
GPIO38 | In | yes | - | SENSOR_CAPN | usually not broken out
GPIO39 | In | yes | - | SENSOR_VN | -
</center>
<b>ADC:</b> these pins can be used as ADC inputs<br>
<b>RTC:</b> these pins are RTC GPIOs and can be used in deep-sleep mode<br>
<b>PU/PD:</b> these pins have software configurable pull-up/pull-down functionality.<br>
@note GPIOs that can be used as ADC channels are also available as low power digital inputs/outputs
in deep sleep mode.
GPIO0, GPIO2 are bootstrapping pins which are used to boot ESP32 in different modes:
<center>
GPIO0 | GPIO2 | Mode
:----:|:-----:|------------------
1 | X | boot in FLASH mode to boot the firmware from flash (default mode)
0 | 0 | boot in UART mode for flashing the firmware
</center><br>
@note GPIO2 becomes the SPI MISO signal for boards that use the HSPI interface
as SD-Card interface in 4-bit SD mode. On these boards all signals of the
SD-Card interface are pulled up. Because of the bootstrapping
functionality of GPIO2, it can become necessary to either press the
**Boot** button, remove the SD card or remove the peripheral hardware
to flash RIOT.
## ADC Channels {#esp32_adc_channels_esp32}
ESP32 integrates two 12-bit ADCs (ADC1 and ADC2) capable of measuring up to
18 analog signals in total. Most of these ADC channels are either connected
to a number of integrated sensors like a Hall sensors, touch sensors and a
temperature sensor or can be connected with certain GPIOs. Integrated sensors
are disabled in RIOT's implementation and are not accessible. Thus, up to 18
GPIOs, can be used as ADC inputs:
- **ADC1** supports 8 channels: GPIOs 32-39
- **ADC2** supports 10 channels: GPIOs 0, 2, 4, 12-15, 25-27
These GPIOs are realized by the RTC unit and are therefore also called RTC
GPIOs or RTCIO GPIOs.
The maximum number of ADC channels #ADC_NUMOF_MAX is 18
@note
- GPIO37 and GPIO38 are usually not broken out on ESP32 boards and can not
be used therefore.
- ADC2 is also used by the WiFi module. The GPIOs connected to ADC2 are
therefore not available as ADC channels if the modules `esp_wifi` or
`esp_now` are used.
- Vref can be read with function #adc_line_vref_to_gpio at GPIO25.
## DAC Channels {#esp32_dac_channels_esp32}
ESP32 SoC supports 2 DAC lines at GPIO25 and GPIO26.
## I2C Interfaces {#esp32_i2c_interfaces_esp32}
ESP32 has two built-in I2C interfaces.
The following table shows the default configuration of I2C interfaces
used for a large number of ESP32 boards. It can be overridden by
[application-specific configurations](#esp32_application_specific_configurations).
<center>
Device | Signal | Pin | Symbol | Remarks
:----------|:-------|:-------|:--------------|:----------------
I2C_DEV(0) | | | `#I2C0_SPEED` | default is `I2C_SPEED_FAST`
I2C_DEV(0) | SCL | GPIO22 | `#I2C0_SCL` | -
I2C_DEV(0) | SDA | GPIO21 | `#I2C0_SDA` | -
</center><br>
## PWM Channels {#esp32_pwm_channels_esp32}
The ESP32 LEDC module has 2 channel groups with 8 channels each. Each of
these channels can be clocked by one of the 4 timers.
## SPI Interfaces {#esp32_spi_interfaces_esp32}
ESP32 has four SPI controllers where SPI0 and SPI1 share the same bus and
are used as interface for external memory:
- Controller SPI0 is reserved for caching external memory like Flash
- Controller SPI1 is reserved for external memory like PSRAM
- Controller SPI2 can be used as general purpose SPI (also called HSPI)
- Controller SPI3 can be used as general purpose SPI (also called VSPI)
Thus, only SPI2 (HSPI) and SPI3 (VSPI) can be used as general purpose SPI
in RIOT as SPI_DEV(0) and SPI_DEV(1) in arbitrary order.
The following table shows the pin configuration used for most boards, even
though it **can vary** from board to board.
<center>
Device |Signal| Pin | Symbol | Remarks
:-----------------------|:----:|:-------|:-----------:|:---------------------------
`SPI0_HOST`/`SPI1_HOST` | SCK | GPIO6 |- | reserved for flash and PSRAM
`SPI0_HOST`/`SPI1_HOST` | CMD | GPIO11 |- | reserved for flash and PSRAM
`SPI0_HOST`/`SPI1_HOST` | SD0 | GPIO7 |- | reserved for flash and PSRAM
`SPI0_HOST`/`SPI1_HOST` | SD1 | GPIO8 |- | reserved for flash and PSRAM
`SPI0_HOST`/`SPI1_HOST` | SD2 | GPIO9 |- | reserved for flash and PSRAM (only in `qio` or `qout` mode)
`SPI0_HOST`/`SPI1_HOST` | SD3 | GPIO10 |- | reserved for flash and PSRAM (only in `qio` or `qout` mode)
`SPI2_HOST` (`HSPI`) | SCK | GPIO14 |`#SPI1_SCK` | can be used
`SPI2_HOST` (`HSPI`) | MISO | GPIO12 |`#SPI1_MISO` | can be used
`SPI2_HOST` (`HSPI`) | MOSI | GPIO13 |`#SPI1_MOSI` | can be used
`SPI2_HOST` (`HSPI`) | CS0 | GPIO15 |`#SPI1_CS0` | can be used
`SPI3_HOST` (`VSPI`) | SCK | GPIO18 |`#SPI0_SCK` | can be used
`SPI3_HOST` (`VSPI`) | MISO | GPIO19 |`#SPI0_MISO` | can be used
`SPI3_HOST` (`VSPI`) | MOSI | GPIO23 |`#SPI0_MOSI` | can be used
`SPI3_HOST` (`VSPI`) | CS0 | GPIO5 |`#SPI0_CS0` | can be used
</center><br>
Some boards use the `HSPI` (`SPI2_HOST`) as SD-Card interface (SDIO) in 4-bit SD mode.
<center>
Device | Pin | SD 4-bit mode | SPI mode
:---------------------|:------:|:-------------:|:----------:
`SPI2_HOST` (`HSPI`) | GPIO14 | CLK | SCK
`SPI2_HOST` (`HSPI`) | GPIO15 | CMD | CS0
`SPI2_HOST` (`HSPI`) | GPIO2 | DAT0 | MISO
`SPI2_HOST` (`HSPI`) | GPIO4 | DAT1 | -
`SPI2_HOST` (`HSPI`) | GPIO12 | DAT2 | -
`SPI2_HOST` (`HSPI`) | GPIO13 | DAT3 | MOSI
</center><br>
@note On these boards, all these signals are pulled up. This may cause
flashing problems due to the bootstrap function of the GPIO2 pin,
see section [GPIO pins](#esp32_gpio_pins_esp32). Therefore, it can
be necessary to either press the **Boot** button, to remove the SD card
or to remove the peripheral hardware to flash RIOT.
## Timers {#esp32_timers_esp32}
ESP32 has two timer groups with two timers each, resulting in a total of
four timers. Since one timer is used as system timer, up to three timers
with one channel each can be used in RIOT as timer devices
TIMER_DEV(0) ... TIMER_DEV(2).
Additionally ESP32 has three CCOMPARE registers which can be used
alternatively as timer devices TIMER_DEV(0) ... TIMER_DEV(2) can be used
in RIOT if the module `esp_hw_counter` is enabled.
## UART Interfaces {#esp32_uart_interfaces_esp32}
ESP32 integrates three UART interfaces. The following default pin
configuration of UART interfaces as used by a most boards can be overridden
by the application, see section [Application-Specific Configurations]
(#esp32_application_specific_configurations).
<center>
Device |Signal|Pin |Symbol |Remarks
:-----------|:-----|:-------|:-----------|:----------------
UART_DEV(0) | TxD | GPIO1 |`#UART0_TXD`| cannot be changed
UART_DEV(0) | RxD | GPIO3 |`#UART0_RXD`| cannot be changed
UART_DEV(1) | TxD | GPIO10 |`#UART1_TXD`| optional, can be overridden
UART_DEV(1) | RxD | GPIO9 |`#UART1_RXD`| optional, can be overridden
UART_DEV(2) | TxD | GPIO17 |`UART2_TXD` | optional, can be overridden
UART_DEV(2) | RxD | GPIO16 |`UART2_RXD` | optional, can be overridden
</center><br>
## JTAG Interface {#esp32_jtag_interface_esp32}
The JTAG interface on ESP32 is connected to the following GPIOs:
<center>
JTAG Signal | ESP32 Pin
:-----------|:-----------
TRST_N | CHIP_PU
TDO | GPIO15 (MTDO)
TDI | GPIO12 (MTDI)
TCK | GPIO13 (MTCK)
TMS | GPIO14 (MTMS)
GND | GND
</center><br>
*/
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