espressif/esp-serial-flasher

readme

# esp-serial-flasher

`esp-serial-flasher` is a portable C library for flashing or loading apps to RAM of Espressif SoCs from other host microcontrollers.

## Using the library
Espressif SoCs are normally programmed via serial interface (UART). The port layer for the given host microcontroller has to be implemented if not available. Details can be found in section below.

Supported **host** microcontrollers:

- STM32
- Raspberry Pi SBC
- ESP32
- Any MCU running Zephyr OS

Supported **target** microcontrollers:

- ESP32
- ESP8266
- ESP32-S2
- ESP32-S3
- ESP32-C3
- ESP32-C2
- ESP32-H2
- ESP32-C6

Supported hardware interfaces:
- UART
- SPI (only for RAM download, experimental)

For example usage check the `examples` directory.

## Supporting a new host target

In order to support a new target, following functions have to be implemented by user:

- `loader_port_read()`
- `loader_port_write()`
- `loader_port_enter_bootloader()`
- `loader_port_delay_ms()`
- `loader_port_start_timer()`
- `loader_port_remaining_time()`

For the SPI interface ports
- `loader_port_spi_set_cs()`
needs to be implemented as well.

The following functions are part of the [io.h](include/io.h) header for convenience, however, the user does not have to strictly follow function signatures, as there are not called directly from library.

- `loader_port_change_transmission_rate()`
- `loader_port_reset_target()`
- `loader_port_debug_print()`

Prototypes of all functions mentioned above can be found in [io.h](include/io.h).

## Configuration

These are the configuration toggles available to the user:

* `SERIAL_FLASHER_INTERFACE_UART/SERIAL_FLASHER_INTERFACE_SPI`

This defines the hardware interface to use. SPI interface only supports RAM download mode and is in experimental stage and can undergo changes.

Default: SERIAL_FLASHER_INTERFACE_UART

* `MD5_ENABLED`

If enabled, `esp-serial-flasher` is capable of verifying flash integrity after writing to flash.

Default: Enabled
> Warning: As ROM bootloader of the ESP8266 does not support MD5_CHECK, this option has to be disabled!

* `SERIAL_FLASHER_RESET_HOLD_TIME_MS`

This is the time for which the reset pin is asserted when doing a hard reset in milliseconds.

Default: 100

* `SERIAL_FLASHER_BOOT_HOLD_TIME_MS`

This is the time for which the boot pin is asserted when doing a hard reset in milliseconds.

Default: 50

Configuration can be passed to `cmake` via command line:

```
cmake -DMD5_ENABLED=1 .. && cmake --build .
```

### STM32 support

The STM32 port makes use of STM32 HAL libraries, and these do not come with CMake support. In order to compile the project, `stm32-cmake` (a `CMake` support package) has to be pulled as submodule.

```
git clone --recursive https://github.com/espressif/esp-serial-flasher.git
```

If you have cloned this repository without the `--recursive` flag, you can initialize the submodule using the following command:

```
git submodule update --init
```

In addition to configuration parameters mentioned above, following definitions has to be set:

- TOOLCHAIN_PREFIX: path to arm toolchain (i.e /home/user/gcc-arm-none-eabi-9-2019-q4-major)
- STM32Cube_DIR: path to STM32 Cube libraries (i.e /home/user/STM32Cube/Repository/STM32Cube_FW_F4_V1.25.0)
- STM32_CHIP: name of STM32 for which project should be compiled (i.e STM32F407VG)
- PORT: STM32

This can be achieved by passing definitions to the command line, such as:

```
cmake -DTOOLCHAIN_PREFIX="/path_to_toolchain" -DSTM32Cube_DIR="path_to_stm32Cube" -DSTM32_CHIP="STM32F407VG" -DPORT="STM32" .. && cmake --build .
```

Alternatively, those variables can be set in the top level `cmake` directory:

```
set(TOOLCHAIN_PREFIX    path_to_toolchain)
set(STM32Cube_DIR       path_to_stm32_HAL)
set(STM32_CHIP          STM32F407VG)
set(PORT                STM32)
```

### Zephyr support

The Zephyr port is ready to be integrated into Zephyr apps as a Zephyr module. In the manifest file (west.yml), add:

```
    - name: esp-flasher
      url: https://github.com/espressif/esp-serial-flasher
      revision: master
      path: modules/lib/esp_flasher
```

And add

```
CONFIG_ESP_SERIAL_FLASHER=y
CONFIG_CONSOLE_GETCHAR=y
CONFIG_SERIAL_FLASHER_MD5_ENABLED=y
```

to the project configuration `prj.conf`.

For the C/C++ source code, the example code provided in `examples/zephyr_example` can be used as a starting point.

## Licence

Code is distributed under Apache 2.0 license.

## Known limitations

Size of new binary image has to be known before flashing.

                                        
                                        # Flash multiple partitions example

## Overview

Example demonstrates how to flash ESP32/ESP32-S2/ESP8266 from another (host) MCU using esp_serial_flash component API. In this case, ESP32 is also used as host MCU. Binaries to be flashed from host MCU to another Espressif SoC can be found in `binaries` folder and are converted into C-array during build process.

Following steps are performed in order to re-program target's memory:

1. Filesystem is initialized and mounted.
2. UART1 through which new binary will be transfered is initialized.
3. Host puts slave device into boot mode tries to connect by calling `esp_loader_connect()`.
4. Binary file is opened and its size is acquired, as it has to be known before flashing.
5. Then `esp_loader_flash_start()` is called to enter flashing mode and erase amount of memory to be flashed.
6. `esp_loader_flash_write()` function is called repeatedly until the whole binary image is transfered.

Note: In addition, to steps mentioned above, `esp_loader_change_transmission_rate`  is called after connection is established in order to increase flashing speed. This does not apply for ESP8266, as its bootloader does not support this command. However, ESP8266 is capable of detecting baud rate during connection phase, and can be changed before calling `esp_loader_connect`, if necessary.

## SPI pin initialization

In majority of cases `ESP_LOADER_CONNECT_DEFAULT` helper macro is used in order to initialize `loader_connect_args_t` data structure passed to `esp_loader_connect`. Helper macro sets `spi_pin_config` field of the data structure to zero, thus, default SPI pins are used to connect to FLASH memory. In special cases, such as custom design in which FLASH is connected to different pins, `spi_pin_config` field has to be set accordingly. For more detailed information refer to [serial protocol](https://docs.espressif.com/projects/esptool/en/latest/esp32s3/advanced-topics/serial-protocol.html).

## Hardware Required

* Two development boards with ESP32 SoC (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.).
* One or two USB cables for power supply and programming.

## Hardware connection

Table below shows connection between two ESP32 devices.

| ESP32 (host) | ESP32 (slave) |
|:------------:|:-------------:|
|    IO26      |      IO0      |
|    IO25      |     RESET     |
|    IO4       |      RX0      |
|    IO5       |      TX0      |

Note: interconnection is the same for all three targets (slaves). 

## Build and flash

To run the example, type the following command:

```CMake
idf.py -p PORT flash monitor
```

(To exit the serial monitor, type ``Ctrl-]``.)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

## Configuration

For details about available configuration option, please refer to top level [README.md](../../README.md). 
Compile definitions can be specified on command line when running `idf.py`, for example:

```
idf.py build -DMD5_ENABLED=1
```
Binaries to be flashed are placed in separate folder (binaries.c) for each possible target and converted to C-array. Without explicitly enabling MD5 check, flash integrity verification is disabled by default.

## Example output

Here is the example's console output:

```
...
I (342) example: Initializing SPIFFS
I (482) example: Image size: 144672
I (902) example: Connected to target
I (1732) example: Start programming
I (1832) example: packet: 0  written: 1024 B
I (1932) example: packet: 1  written: 1024 B
...
I (16052) example: packet: 140  written: 1024 B
I (16152) example: packet: 141  written: 288 B
I (16152) example: Finished programming
```

                                    

                                        
                                        # Example of loading the program into RAM through SPI

## Overview

This example demonstrates how to upload an app to RAM of an Espressif MCU with SPI download support from another (host) MCU using the `esp_serial_flash` component API. In this case, another Espressif MCU is used as the host. Binaries to be uploaded to RAM from host MCU to the target MCU can be found in `binaries/RAM_APP` folder and are converted into C-array during build process.

Following steps are performed in order to re-program the target's memory:

1. SPI2 through which the binary will be transfered is initialized.
2. Host puts slave device into SPI download mode tries to connect by calling `esp_loader_connect()`.
3. Then `esp_loader_mem_start()` is called for each segment in RAM.
4. `esp_loader_flash_write()` function is called repeatedly for every segment until the whole binary image is transfered.
5. `esp_loader_mem_finish()` is called with the binary entrypoint, telling the chip to start the uploaded program.
6. UART2 is initialized for the connection to the target
7. Target output is continually read and printed

## Hardware Required

* Two development boards, one with any Espressif MCU (e.g., ESP32-DevKitC, ESP-WROVER-KIT, etc.) and one with an Espressif MCU with SPI download support. Here is a short list of supported MCUs:
1. ESP32-C3
2. ESP32-C2
3. ESP32-S3
4. ESP32-S2
5. ESP32-H2
* One or two USB cables for power supply and programming.

## Hardware connection

Table below shows connection between two Espressif MCUs.

| Host         | Slave         |
|    IO_5      |    RESET      |
|    IO_12     |    CLK        |
|    IO_10     |    CS         |
|    IO_13     |    MISO       |
|    IO_11     |    MOSI       |
|    IO_14     |    QUADWP     |
|    IO_9      |    QUADHD     |
|    IO_13     |    STRAP_B0   |
|    IO_2      |    STRAP_B1   |
|    IO_3      |    STRAP_B2   |
|    IO_4      |    STRAP_B3   |
|    IO_6      |    UART0_RX   |
|    IO_7      |    UART0_TX   |

> Note 1: Strapping bit pins are documented in the TRM for each respective chip

> Note 2: For achieving highest speeds, check which pins go through the IO MUX bypassing the GPIO matrix and use those. Pins chosen here are IO MUX pins for ESP32S3 and ESP32S2 chips.

## Build and flash

To run the example, type the following command:

```CMake
idf.py -p PORT flash monitor
```

(To exit the serial monitor, type ``Ctrl-]``.)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

## Example output

Here is the example's console output:

```
Connected to target
I (682) spi_ram_loader: Loading app to RAM ...
Start loading
Downloading 7840 bytes at 0x3fc96e00...
Downloading 312 bytes at 0x3fca0020...
Downloading 93164 bytes at 0x40380000...
Finished loading
I (802) spi_ram_loader: ********************************************
I (802) spi_ram_loader: *** Logs below are print from slave .... ***
I (812) spi_ram_loader: ********************************************
Hello world!
Hello world!
...
```