OpenMV MicroPython libraries

Warning

Important summary of this section

  • MicroPython provides built-in modules that mirror the functionality of the Python standard library (e.g. os, time), as well as MicroPython-specific modules (e.g. bluetooth, machine).

  • Most Python standard library modules implement a subset of the functionality of the equivalent Python module, and in a few cases provide some MicroPython-specific extensions (e.g. array, os)

  • Due to resource constraints or other limitations, some ports or firmware versions may not include all the functionality documented here.

  • To allow for extensibility, some built-in modules can be extended from Python code loaded onto the device filesystem.

This chapter describes modules (function and class libraries) which are built into MicroPython. This documentation in general aspires to describe all modules and functions/classes which are implemented in the MicroPython project. However, MicroPython is highly configurable, and each port to a particular board/embedded system may include only a subset of the available MicroPython libraries.

With that in mind, please be warned that some functions/classes in a module (or even the entire module) described in this documentation may be unavailable in a particular build of MicroPython on a particular system. The best place to find general information of the availability/non-availability of a particular feature is the “General Information” section which contains information pertaining to a specific MicroPython port.

On some ports you are able to discover the available, built-in libraries that can be imported by entering the following at the REPL:

help('modules')

Beyond the built-in libraries described in this documentation, many more modules from the Python standard library, as well as further MicroPython extensions to it, can be found in micropython-lib.

Python standard libraries and micro-libraries

The following standard Python libraries have been “micro-ified” to fit in with the philosophy of MicroPython. They provide the core functionality of that module and are intended to be a drop-in replacement for the standard Python library.

OpenMV Cam libraries

The following sections describe the libraries available on each OpenMV-supported board, including both the MicroPython-specific built-ins and OpenMV’s own extensions.

Common modules

Built into the firmware on every OpenMV camera board.

Frozen Python helpers shipped on most OpenMV camera boards (drivers, networking, and utilities):

Networking helpers (require a working network interface):

Port-specific modules

Modules tied to a specific MCU family. See the per-board sections below for which boards include each one.

Hardware drivers

Drivers for sensors, displays and other peripherals shipped on one or more OpenMV-supported boards. See the per-board sections below for which boards include each one.

Per-board availability

The lists below show which port-specific and driver modules are shipped on each board. All the modules in Common, Frozen Python helpers, and Networking helpers (above) are available on every camera board unless otherwise noted.

OpenMV N6

STM32N657 (Cortex-M55 @ 800 MHz) with a 1 GHz on-chip NPU rated at 600 GOPS INT8. Pairs the NPU with the PAG7936 1 MP global-shutter sensor.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

OpenMV AE3

Alif Ensemble E3 dual-core SoC: Cortex-M55 @ 400 MHz (HP) plus Cortex-M55 @ 160 MHz (HE), with two on-chip NPUs (400 MHz / 204 GOPS HP NPU + 160 MHz / 46 GOPS HE NPU).

  • alif — Alif Ensemble SoC functions

  • lsm6dsox — LSM6DSOX 6-axis IMU

  • romfs — ROMFS helper utilities

  • pca9674a — PCA9674A I2C expander driver

OpenMV Cam RT1062

Low-power machine-vision board around the NXP i.MX RT1062 (Cortex-M7 @ 600 MHz). Combines USB-C high-speed networking, Wi-Fi / Bluetooth and 10/100 Ethernet.

  • mimxrt — functionality specific to NXP i.MX RT

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

  • pca9674a — PCA9674A I2C expander driver

OpenMV Pure Thermal

Full-system thermal imaging board around the STM32H743 (Cortex-M7 @ 480 MHz) with 64 MB external SDRAM, 32 MB QSPI flash, a hardware JPEG codec and DVI/HDMI output.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • tfp410 — DVI/HDMI serializer

  • ft5x06 — capacitive touchscreen driver

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

OpenMV Cam H7 Plus

STM32H743 (Cortex-M7 @ 480 MHz) with 32 MB external SDRAM, 32 MB QSPI flash, a hardware JPEG codec and the OV5640 5MP camera module.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

OpenMV Cam H7

STM32H743 (Cortex-M7 @ 480 MHz) with 1 MB internal SRAM, 2 MB internal flash and a hardware JPEG codec.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

OpenMV Cam M7

STM32F765 (Cortex-M7 @ 216 MHz) with 512 KB internal SRAM and 2 MB internal flash. Bundled with the OV7725 sensor.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

OpenMV Cam M4

STM32F427 (Cortex-M4 @ 180 MHz) with 256 KB internal SRAM and 1 MB internal flash. Bundled with the OV7725 sensor.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

Arduino Nicla Vision

22.86 × 22.86 mm machine-vision board around the STM32H747AII6 dual-core SoC: Cortex-M7 @ 400 MHz plus Cortex-M4 @ 200 MHz.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • lsm6dsox — LSM6DSOX 6-axis IMU

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • ds18x20 — DS18x20 temperature sensor driver

  • onewire — 1-Wire bus protocol

  • neopixel — control of WS2812 / NeoPixel LEDs

Arduino Portenta H7

66 × 25 mm industrial dev board around the STM32H747XI dual-core SoC: Cortex-M7 @ 400 MHz plus Cortex-M4 @ 200 MHz.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • ds18x20 — DS18x20 temperature sensor driver

  • onewire — 1-Wire bus protocol

  • neopixel — control of WS2812 / NeoPixel LEDs

  • lora — LoRa modem driver

  • ssd1306 — OLED driver

  • tb6612 — TB6612 motor driver

Arduino Giga R1 WiFi

101 × 53 mm Mega-form-factor board around the STM32H747XI dual-core SoC: Cortex-M7 @ 480 MHz plus Cortex-M4 @ 240 MHz, with an on-board 800x480 touchscreen.

  • pyb — functions related to the board

  • stm — functionality specific to STM32 MCUs

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • neopixel — control of WS2812 / NeoPixel LEDs

  • gt911 — GT911 5-point capacitive touch controller

  • ft5x06 — capacitive touchscreen driver

Arduino Nano RP2040 Connect

RP2040-based Nano-form-factor board with the U-blox NINA-W102 Wi-Fi/Bluetooth module. No longer actively supported; the last OpenMV firmware release for this board is retained for archival use.

  • rp2 — RP2040-specific PIO / DMA / flash helpers

  • espflash — ESP32 ROM bootloader firmware flasher

  • lsm6dsox — LSM6DSOX 6-axis IMU

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

Arduino Nano 33 BLE Sense

Nordic nRF52840 Nano-form-factor board with the on-board Arduino sensor suite. No longer actively supported; the last OpenMV firmware release for this board is retained for archival use.

  • ubluepy — Bluetooth LE peripheral and central API on the Nordic SoftDevice

  • bmi270 — BMI270 6-axis IMU

  • bmm150 — BMM150 3-axis magnetometer

  • lsm9ds1 — LSM9DS1 9-axis IMU

  • hts221 — HTS221 humidity/temperature sensor

  • lps22h — LPS22HB/HH pressure sensor

  • hs3003 — HS3003 humidity/temperature sensor

  • apds9960 — proximity, gesture, and color sensor driver

  • dht — DHT11 and DHT22 temperature/humidity sensors

  • onewire — 1-Wire bus protocol

  • ds18x20 — DS18x20 temperature sensor driver

  • neopixel — control of WS2812 / NeoPixel LEDs

Extending built-in libraries from Python

A subset of the built-in modules are able to be extended by Python code by providing a module of the same name in the filesystem. This extensibility applies to the following Python standard library modules which are built-in to the firmware: array, binascii, collections, errno, gzip, hashlib, heapq, io, json, os, platform, random, re, select, socket, ssl, struct, time, zlib, as well as the MicroPython-specific machine module. All other built-in modules cannot be extended from the filesystem.

This allows the user to provide an extended implementation of a built-in library (perhaps to provide additional CPython compatibility or missing functionality). This is used extensively in micropython-lib, see Package management for more information. The filesystem module will typically do a wildcard import of the built-in module in order to inherit all the globals (classes, functions and variables) from the built-in.

In MicroPython v1.21.0 and higher, to prevent the filesystem module from importing itself, it can force an import of the built-in module by temporarily clearing sys.path during the import. For example, to extend the time module from Python, a file named time.py on the filesystem would do the following:

_path = sys.path
sys.path = ()
try:
  from time import *
finally:
  sys.path = _path
  del _path

def extra_method():
  pass

The result is that time.py contains all the globals of the built-in time module, but adds extra_method.

In earlier versions of MicroPython, you can force an import of a built-in module by appending a u to the start of its name. For example, import utime instead of import time. For instance, time.py on the filesystem could look like:

from utime import *

def extra_method():
  pass

This way is still supported, but the sys.path method described above is now preferred as the u-prefix will be removed from the names of built-in modules in a future version of MicroPython.

Other than when it specifically needs to force the use of the built-in module, code should always use import module rather than import umodule.