For programming ESP32 board with Arduino IDE first step is to add ESP32 board support on Arduino IDE. The BLE Scanner application is used to see the device and interact with the data. After storing the tokens, the ESP32 reboots in MQTT (IoT) mode and Feb 13, 2020 · All you need to do is connect a membrane keypad up to the GPIO pins on the ESP32. The ESP32 is initially started in Bluetooth mode. bin Firmware Jan 17, 2021 · Sun Jan 17, 2021 2:34 pm. To use it, just have a serial communication application via BLE on the smartphone (I use the Serial Bluetooth Terminal). I want to transfer joystick data from one esp32 to another, so that I can make a remote controlled car. 12. These are based on the existing multi_bluetooth tests that are in the main repo. The ESP32 is a microcontroller that provides an API for Bluetooth A2DP which can be used to receive sound data e. # This example demonstrates a peripheral implementing the Nordic UART Service (NUS). py --chip esp32 --port /dev/ttyUSB0 erase_flash From then on program the firmware starting at address 0x1000: esptool. A Bluetooth controller "host" for the ESP32, ESP32-S3, ESP32-C3, Raspberry Pi Pico W and Posix (Linux, macOS). And vice versa, the ESP32 chip is a great platform for using MicroPython. I asked chatGPT and it gave me many codes using the bluetooth module and the BluetoothSocket class, but it seems like the May 23, 2022 · The UART protocol is useful when a microcomputer or other master microcontroller guides networked microcontroller systems like ESP8266 or ESP32. # Set the EoL characters to \r\n. bin) Top Select “Install” button and then press “BOOT” switch on the ESP32 board. py. We can avoid configuring a Bluetooth device using AT commands and save two GPIO pins. This API is intended to match the low-level Bluetooth protocol and May 10, 2019 · Serial to Serial Bluetooth. History. Mar 24, 2017 · All ESP32 boards running MicroPython. Currently this supports Bluetooth Low Energy (BLE) in Central, Peripheral,Broadcaster, and Observer roles, as well as GATT Server and Client and L2CAPconnection-oriented-channels. Configure ESP32 WiFi over Bluetooth. 12 (esp32-idf4-20191220-v1. Improve this question. Wrapping Up. bluetooth— low-level Bluetooth¶. The CORE ESP32 development board is designed based on the ESP32-C3 chip from Espressif Systems. Now, turn your ESP32 off and turn it back on again and see that the ONBOARD LED starts to blink. 23. Dec 25, 2020 · Re: Sending data from mobile device to micropython device over bluetooth. It has a powerful 240MHz dual core microcontroller with 520K of SRAM. 2. ESP32 can be programmed by many ways including Arduino ESP32 MicroPython Project to scan for nearby Bluetooth Low Energy Devices to determine the room utilization. It is an ideal controller for robot projects. . I got some of the very cute XAIO ESP32C3 micro-controllers that support Bluetooth LE. Connect the Android with Bluetooth of ESP32 in Serial Bluetooth Terminal ubluetooth. Control LEDs by ESP32 and smartphone via Bluetooth. So given that all you want to do is pretend to be a non-functional HFP profile device, it might be quite Nov 20, 2021 · Unlock new career opportunities and become data fluent today! Use my link https://bit. me/+bSRaH6xTDCxjZTMxESP32: https://t. A device may operate in multiple roles concurrently. The ESP32 SDK provides two different Bluetooth stacks -- NimBLE (whcih only does BLE) or BlueDroid (which does both). In this program you can modify parameters such as name, PIN code and communication speed in baudrate. This tutorial will guide you through setting up MicroPython, getting a prompt, using WebREPL, connecting to the network and communicating with the Internet, using the hardware peripherals, and ports/unix/ -- a version of MicroPython that runs on Unix. That’s the first thing you need to do to start programming your boards with MicroPython: flash/upload the firmware. 12-169 with idf 3. by Peacekeep3r » Tue Jul 26, 2022 12:20 am. Oct 9, 2021 · I will only very briefly discuss Wi-Fi and Bluetooth. 0-1. javargas26. Open your Arduino IDE, and go to File > Examples > BluetoothSerial > SerialtoSerialBT. On the other hand, Apache NimBLE based stack is Bluetooth Low Energy only. LOG_NONE" can not hide those messages mentioned. 100 Hz from a mobile sensor (ESP32-DevKitC V4) and send them to my Win10 PC via bluetooth. Jun 23, 2023 · Wi-Fi and Bluetooth connectivity: With the Nano ESP32, you can tap into the impressive capabilities of the ESP32-S3 microcontroller, a widely recognized and acclaimed choice in the IoT realm. You know now have an idea on how MicroPython works in the ESP32. Pinout of the ESP32. The standard mode is without PSRAM you can activate that using the argument fb_location=camera. I dont find any specific package to use, just from machine import UART, but i dont think that will happen, i dont even know wich Tx/Rx the ble is connected, and if I have to active it to use, or if is already on. Hi, I am developing a code and it is like that at the moment. A platform for writing and freely expressing thoughts on various topics. sleep(1) Now, copy the file to the ESP32: ampy -p /dev/ttyUSB0 put main. 0 update enabled BLE for ESP32 based-boards. ) Download the latest release of this library from the release page. Jun 19, 2023 · Step 4: Setting Up Android App. 4 GHz ISM (Industrial, Scientific and Medical) frequency band, Bluetooth is a short-range wireless communication technology with range up to 100 m. Otherwise the sections are mostly self contained, so feel free to skip to those that interest you. The ESP32 SDK provides two different Bluetooth stacks -- NimBLE (which only does BLE) or BlueDroid (which does both). For this follow the steps below: May 9, 2019 · ESP32 Bluetooth Low Energy Applications using Zerynth. ESP32 boards are great for IoT projects because they support Wi-Fi, Bluetooth Classic, and Bluetooth Low Energy. 12-182-g1fccda049. For most # applications, we recommend using the higher-level aioble library which takes # care of all IRQ handling and connection management. Part 2 – ESP32 BLE client. Feb 21, 2020 · How can I use bluetooth in esp32 with micropython?? (Firmware built with ESP-IDF v3. The unit of communication is a character (not to be confused with a string character) which can be 8 or 9 bits wide. Nov 4, 2022 · L’objectif de ce tutoriel est d’allumer à distance 3 LEDs connectées à la carte ESP32 par un Smartphone par l’intermédiaire du bluetooth. To use the ESP32 in a robot, you will need to connect it to the robot’s hardware, such as motors, sensors, and other components. Send Data from Raspberry Pi Pico to Android App Using BLE. Currently this supports Bluetooth Low Energy (BLE) in Central, Peripheral, Broadcaster, and Observer roles, as well as GATT Server and Client and L2CAP connection-oriented-channels. This article helps you enable the Bluetooth (BLE) module on the M5Stack running MicroPython. At the physical level it consists of 2 lines: RX and TX. I don’t know if the Generic Access Service is immutable or there is something wrong with my method? My ESP32 board firmware is v1. Mar 24, 2018 · Just pushed a getting started guide for the great #ESP32 and #Micropython based on a class I’m teaching. Many examples are available – going from a simple scanner to beacons to a more advanced GATT server. Target audience: MicroPython users with an ESP32 board. # Proof-of-concept of a REPL over BLE UART. MicroPython tries to provide a generic port which would run on as many boards/modules as possible, but there may be limitations. We’re using default UUIDs for services and characteristics already defined in the SIG (Bluetooth Special Interest Group). py --chip esp32 --port /dev/ttyUSB0 --baud 460800 write_flash -z 0x1000 esp32-20190125-v1. The IMU data and the buttons' states are sent over BLE and the display can be controlled writing a variable. This tutorial is intended to get you started using MicroPython on the ESP32 system-on-a-chip. 19. Code. It can be used in a robot to provide wireless communication and control. x on microcontrollers and small embedded systems. MicroPython Jun 11, 2022 · 06-11-22 2820. 2 posts • Page 1 of 1. I'm working on an application at ESP32, which is reporting to a smartphone. ESP32 is a microcontroller has builtin Wifi and dual mode Bluetooth support. chamal Posts: 1 Joined: Fri Apr 05, 2019 8:06 am. 3 posts • Page 1 of 1. Now the ESP32 will be identified as removable mass storage drive on PC or Laptop, and contains a “boot. x, with support for BLE, LAN and PPP:GENERIC : esp32-idf3-20200219-v1. Aug 3, 2023 · Now, I can successfully send data from the app to my ESP32, but encountering an issue when sending data back from ESP32 to the app. If it is your first time it is recommended to follow the tutorial through in the order below. Apr 25, 2018 · DFRobot Apr 25 2018 4579. Dec 10, 2019 · Re: Can A ESP32 Masquerade As A Bluetooth Headset? by jimmo » Wed Dec 11, 2019 2:35 am. ble_uart_repl. MicroPython machine module. Aug 5, 2021 · In this video, I will discussed how you can use a Bluetooth Low Energy BLE module with ESP32 using MicroPython. Jul 25, 2022 · ESP32 Bluetooth " [Errno 12] ENOMEM" after a few seconds. ports/stm32/ -- a version of MicroPython that runs on the PyBoard and similar STM32 boards (using ST's Cube HAL drivers). 21. Instructions can be found here. bluetoothのライブラリがポーティングされています。. Follow asked Sep 12, 2022 at 6:01. tests/ -- test framework and test scripts. It can be programmed through various programming platforms like Arduino IDE. 14. # This example demonstrates the low-level bluetooth module. A BLE terminal works fine with both the Arduino IDE and MicroPython codes, but in Thunkable, only the Arduino code works for receiving data. Watch on. com/2022/06/micropython-bluetooth-ble-exampls We would like to show you a description here but the site won’t allow us. StartScanning " and then set ListPickerBLE. This process, erases the flash and then installs the MicroPython on ESP32 development board. 1. 2019/10/19. For more details, visit my blog post at:https: Sep 12, 2022 · bluetooth-lowenergy; esp32; micropython; Share. ESP32でも使用できるようになっているので、試してみました Feb 20, 2020 · A part of the code is commented out in the fake code. //BLE server name #define bleServerName "ESP32_BME280" Bluetooth UUIDs. ports/minimal/ -- a minimal MicroPython port. Jun 26, 2022 · This video just show how MicroPython bluetooth module examples run on ESP32-C3. ly/3HD0Exi and check out the first chapter of any DataCamp course for F time. This project is divided into two parts: Part 1 – ESP32 BLE server. Terminal: Font size (14), Font style (Normal), Charset (UTF-8), Display mode (Text), Auto scroll (on), Show connection messages (on In this guide, we’ll provide you with all the information to master Bluetooth (Classic and Low Energy) with the ESP32 in no time. Start with this if you want to port MicroPython to another microcontroller. 84 lines (66 loc) · 1. bin Firmware ESP32C3-Bluetooth-Example. The code is available at Blo Jan 30, 2020 · Micropython is powerful and can be used on to ESP32 to explore all functions inluding WIFI & Bluetooth. Multitude of boards¶ There is a multitude of modules and boards from different sources which carry the ESP32 chip. _ADV_TYPE_FLAGS = const(0x01) Feb 4, 2021 · Hello, hardware: ESP32-WROOM-32 board firmware: esp32-idf3-20210202-v1. x Nov 29, 2017 · Re: Bluetooth on ESP32 running micropython. WARNING: this project is in beta stage and is subject to changes of the code-base, including project-wide name changes and API changes. Cannot retrieve latest commit at this time. A device may operate in multiple rolesconcurrently. This is a comprehensive guide that compiles several of our previous projects in a logical way to make A few aioble (asyncio bluetooth low energy) examples of Micropython using ESP32 (C) 2023-2024 ekspla. import bluetooth. Also contains a Webinterface that features: MQTT Client Integration to receive data from ESP32 MicroController; InfluxDB Integration to write data to database; Responsive Nivo Charts Implementation to visualize data Jul 16, 2017 · Raspberry Pi ESP32 MicroPython Tutorial. me/+aKBKD8v8ZcZjODgxSTM32: https://t. Bluetooth Classic can only be provided by the ESP32. GUI-O application then connects via Bluetooth and the user manually enters the IoT communication tokens. I'm having trouble connecting the two esp32 devices. I would like to get several data values with approx. This repository adds camera (OV2640) support to MicroPython for the ESP32 family. Worth mentioning though -- to answer your specific question, yes the ESP32 can do this right now if you write C code against the IDF using Bluedroid. MicroPythonの更新状況のウオッチを最近さぼっていたのですが、気がついたら汎用のBLEプロトコルスタックのモジュールが追加されていました。. MicroPython provides built-in modules that mirror the functionality of the Python standard library (e. I found one in C++ and one in Python, but the Python one was obsolete and didn't work. I have explained the pins of the ESP32 and their functions in detail here. — low-level Bluetooth. Look around, find more MicroPython resources and explore. py” dummy start up file. 1. The purpose of this project is to create a dual-joystick analog gamepad that will be transmitting over BLE the values using an ESP32 device. # This example demonstrates a UART periperhal. The following examples contain detailed walkthroughs: GATT Client Example Walkthrough. 0 and aioble on ESP32-DevKitC-32E. The objective of this ESP32 Bluetooth tutorial is to explain how to find the device programmatically using Pybluez, a Python module that allows us to use the Bluetooth resources of a computer. Apr 20, 2022 · Hi all Im am using micropython ubluetooth and I can connect to the ESP32 using "Serial bluetooth terminal" But when I try to us MIT App Inventor the only time I can see it in List Picker if I use "call BluetoothE1. 10. micropython-camera-driver. Oct 26, 2023 · In the following line, you can define the name of your BLE device. You can now go to "File" -> "Examples" -> "ESP32 BLE Mouse" and select any of the examples to get started. For users to make a choice: For usecases involving classic Bluetooth as well as Bluetooth The following example shows how to manually pair GUI-O application with ESP32 in MQTT (IoT) mode using Bluetooth connection. But, thank you for the hint. Short repetition: Switching and The ESP32 is a popular WiFi and Bluetooth enabled System-on-Chip (SoC) by Espressif Systems. from your Mobile Phone and makes it available via a callback method. Step 1: Connect Pushbutton with Raspberry Pi Pico W. For compatibility with other ports Bluetooth® API. https://embedded-things. Regarding the long payload greater than 20 bytes I can not confirm. We hope you’ve found this tutorial useful. The ESP32 is a very inexpensive versatile chip designed for efficient Wi-Fi and Bluetooth including BLE. The Serial Bluetooth Terminal is used as a central device. 設定は、メニューバーの"ツール" - "Options"より設定できます。. Follow the next tutorial to flash MicroPython firmware on your board: Flash/Upload MicroPython Firmware to ESP32 and ESP8266. Enjoy reliable and high-speed wireless connectivity, enabling your projects to effortlessly connect to networks, communicate with other devices, and Apr 1, 2024 · A Brief Note of ESP32 Bluetooth. os, time), as well as MicroPython-specific modules (e. blogspot. MicroPython 1. タブ - "インタプリタ". You can find the official website at micropython. ZIP Library" and select the file you just downloaded. Drag and drop the needed python (“. PSRAM. I have worked with several code examples from the Git and they all work - until after a few seconds UART implements the standard UART/USART duplex serial communications protocol. C’est pour cela, on va créer deux programmes: une application mobile avec App Inventor pour le smartphone et un programme micropython pour la carte ESP32. Nov 11, 2021 · The ESP32 client connects to the BLE server and it is notified of its temperature and humidity characteristic values. Using MicroPython is a great way to get the most of your ESP32 board. BLE drivers are now available, including support for secure pairing and scanning; Refer to the official doc for more info. Thus, you are able to take photos with more resolution. For most # applications, we recommend using the higher-level aioble library which takes # care of all IRQ handling and connection Thonny IDE is a great IDE to program the ESP32 and ESP8266 boards using MicroPython. bin). The documentation can be found here. ubluetooth. It's worth noting that L2Cap is specified as the transfer protocol for BLE Object Transfer Service and, as such, is a key protocol in the BLE stack. The ESP32 does technically support BT Classic but there are currently no MicroPython bindings for it. # # Tested with the Adafruit Bluefruit app on Android. It is compatible with Windows, Mac OS X, and Linux and it is easy to install. We have an article with a compilation of several MicroPython IDEs compatible with the ESP32 and ESP8266 boards that you can check below: MicroPython IDEs for ESP32 and ESP8266 Dual analog joystick on ESP32 over BLE (Nordic UART Service - NUS) using micropython. Mar 2, 2020 · Nope, on my ESP32 the parameter "esp. You can configuring the module HC-06 by runnig the file BT_setup. It has a small form factor and stamp hole design, making it convenient for developers to use. Currently I'm testing the Android part of it. Using the @adafruit Huzzah32, install Micropython, connect to WiFi, understand workflow, and many examples #servo #led #analog #multitasking #wifi If you are putting MicroPython on your board for the first time then you should first erase the entire flash using: esptool. Check it out and give it a test run Mar 24, 2021 · time. 39 1 1 silver ble_simple_peripheral. This video shows the implementation of BLE using ESP32 and Micropython. We’ll call it ESP32_BME2820, but you can call it any other name. In the Arduino IDE go to "Sketch" -> "Include Library" -> "Add . Step 2: MicroPython Example Code To Read Data Over Bluetooth LE. The pinout is: Pinout of the ESP32 with MicroPython. Its a Google Flutter application. If this is your first time dealing with the OLED display using MicroPython, we recommend following the getting started guide first: MicroPython: OLED Display with ESP32 and ESP8266; We have a similar tutorials, but using Arduino IDE: ESP32 is a series of low cost, low power system on a chip microcontrollers with integrated Wi-Fi and dual-mode Bluetooth. me/+ECxvJ6H-k May 2, 2023 · Connecting two esp32 devices via bluetooth using micropython. 接続されているCOM を選択. The Bluedroid based stack (default) supports classic Bluetooth as well as Bluetooth Low Energy (Bluetooth LE). To my knowledge, neither the official beta port for the ESP32 nor the fork by loboris have working support for Bluetooth yet. 今回使用しているESP32用のMicroPythonファームには、. Thonnyをインストールし、以下の設定を行います。. But apparently loboris is currently working on adding support to his fork. Thanks @mocleiri for the info and the Mar 21, 2023 · 0. However, Bluetooth Classic support for ESP32 in MicroPython would be useful. Step 3: Connect To Android App & Read Data. Step 5: Toggle the Onboard LED Via Bluetooth App. Apart from reducing the hardware count by one, we can have full Bluetooth control in our MicroPython programs. Apr 29, 2021 · The project is open-sourced under the MIT License. The ESP32 is a microcontroller that features Bluetooth connectivity. [中文] ESP-IDF currently supports two host stacks. The output is a PCM data stream, decoded from SBC format. by SpotlightKid » Thu Nov 30, 2017 1:50 am. UART objects can be created and initialised using: Saved searches Use saved searches to filter your results more quickly Contribute to 2black0/MicroPython-ESP32-BLE development by creating an account on GitHub. 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 HC-06 configuration. bin) また、bluetooth機能を制御するためのドキュメントは、下記に記載されています。. py In this progran you can verify that the hardware is working. 0) Features: WiFi, BT, Dual Core, 240MHz, VRef calibration in efuse, Coding Scheme None. Add Bluetooth gamepad, mouse and keyboard support to your projects easily. The only difference to the pin assignment in the Arduino implementation is the position of the I2C pins. Jan 21, 2023 · Detecting chip type ESP32 Chip is ESP32-D0WDQ6 (revision v1. Zerynth r2. Currently this supports Bluetooth Low Energy (BLE) in Central, Peripheral, Broadcaster, and Observer roles, and a device may operate in multiple roles concurrently. Mac and Linux: instructions – ESP32 Board in Arduino IDE. 1 day ago · MicroPython tutorial for ESP32. This API is intended to match the low-level Bluetooth Apr 5, 2019 · Target audience: MicroPython users with an ESP32 board. Jul 11, 2022 · MicroPythonのBluetooth. In other words, it allows you to control a robot using a DualSense controller. g. Both codes have the same TX UUID set as NOTIFY and READ (see pictures For the overview of the ESP32 Bluetooth stack architecture, follow the links below: ESP32 Bluetooth Architecture (PDF) Code examples for this API section are provided in the bluetooth/bluedroid directory of ESP-IDF examples. NEW: The camera uses now the PSRAM. The board supports multiple interfaces, including UART, GPIO, SPI, I2C, ADC, and PWM, and is ideal for mobile devices, wearable electronics, and IoT applications with low-power performance. メニューを閉じると、"Shell"にMicroPythonの起動ログが表示 Bluepad32. The ESP32 series employs either a Tensilica Xtensa LX6, Xtensa LX7 or a RiscV processor, and both dual-core and single-core variations are available. bluetooth, machine). A project example is included that uses the BLE module to send Oct 7, 2023 · bluetooth. So with two seemingly the same ESP32-WROOM modules, why does one connect and the other doesn't? They are running the same MicroPython code and the same firmware (esp32-20220618-v1. py If you are putting MicroPython on your board for the first time then you should first erase the entire flash using: esptool. I have already connected using BLE but now i need the BT classic. Operating in the unlicensed 2. import bluetooth import io import os import micropython from micropython import const import machine from Mar 25, 2019 · Re: ESP32 bluetooth basic support Post by mattyt » Thu May 09, 2019 5:57 am It's great that you've taken the initiative but Bluetooth support is in active development; please take a look at PR #4589 . I went looking for a code example. At the very least, Thonny is a great solution for remote MicroPython programming of WiFi embedded modules. This ESP32 is connected to an OLED display and it prints the latest readings. The tests of this tutorial were performed using a DFRobot’s ESP32 module device integrated in a ESP32 development board. sleep_ms(1000) And here is the library I used : import struct. Unlike other boards, MicroPython isn’t flashed onto the ESP32 or ESP8266 by default. This API is intended to match the low-level Bluetooth protocol and Mar 3, 2021 · Hi! Im trying to use the bluetooth that already exists in esp32 dev kit's board, but I was not able to find the package to make that work. Micropython does NOT support bluetooth classic on ESP32 (which is required for PS3 controller) The ESP32 does technically support BT Classic but there are currently no MicroPython bindings for it. bin Firmware Nuevos grupos de Telegram para el canal:Microcontroladores: https://t. Footer Mar 27, 2020 · Re: example BLE micropython. "MicroPython (ESP32)" を選択. The multitests directory provides tests that can be run with MicroPython's run-multitests. So here is a simple example in Python that implements a URT device. We’ll program the ESP32 using Arduino IDE, so make sure you have the ESP32 add-on installed before proceeding: Windows: instructions – ESP32 Board in Arduino IDE. Apr 7, 2020 · To draw shapes you need to import the Adafruit GFX MicroPython library. Adding in a battery is a nice touch, and you probably would want to put it into a enclosure of some sort, but as a Jul 26, 2020 · ESP32 - MicroPython - Bluetooth. bin I login ESP32 by putty, and run commands as following: >>> from ubluetooth import BLE This is the MicroPython project, which aims to put an implementation of Python 3. This article will look at the UART class of the MicroPython machine module and explore how that can be used for serial data communication in ESP8266 and ESP32. # Advertising payloads are repeated packets of the following form: # 1 byte data length (N + 1) # 1 byte type (see constants below) # N bytes type-specific data. MUHAMMED SHAFEERALI P MUHAMMED SHAFEERALI P. Bluetoothモジュールはボード上のBluetoothコントローラーへのインターフェースを提供していて，Bluetooth Low Energy (BLE)をサポートしています．セントラル (Central)，ペリフェラル (Peripheral)，ブロードキャスター (Broadcaster)，オブザーバー (Observer A Zhihu column offering a platform for free expression and creative writing. Take a look at L2Cap; it's a way to perform connection-oriented transfers with BLE. The following examples were tested with micropython 1. This tutorial demonstrates how to set up and program an ESP32 device running MicroPython from a Raspberry Pi. ESP32 is a series of low cost, low power system on a chip microcontrollers with integrated Wi-Fi and dual-mode Bluetooth. Bluetooth is a great wireless communication technology that has been popular for quite few years. since it has integrated wifi and bluetooth Thonnyの設定. This module provides an interface to a Bluetooth controller on a board. py script. Pairing (and bonding) is supported on some ports. ble_uart_peripheral. 96 KB. ElementsFromString to BluetoothLE. DeviceList" and I see the device as "24:62:AB:F2:86:2E DS18B20 Teperature -55" I guess the -55 is the Oct 19, 2019 · ESP32のMicroPythonでBluetooth（BLE）を試す. I intend to replace the Generic Access Service for changing the Device Name (default is ESP32) but it also fails. Connect to it with a Bluetooth terminal and If you are putting MicroPython on your board for the first time then you should first erase the entire flash using: esptool. org . The ESP32 is a popular WiFi and Bluetooth enabled System-on-Chip (SoC) by Espressif Systems. hg pz ok ep zd zt ua fx hn pi