![]() You can tell because the resistors go to GND instead. That board also has pull-downs on A0, A1, A2 so the default sub-address is 0. Here's the schematic for the Adafruit MCP9808 and you can see the resistors (R1 and R2, 10K ohms) pulling up to VDD. Many of the breakout boards you can buy at Adafruit or Sparkfun already have the pull-up resistors on them. One on the SDA line and one on the SCL line. Since floating is bad, the I2C bus must have pull-up resistors. It's either floating, or it's pulled low. This is how the transistors are wired, and the details aren't important, however the important thing is this:īoth the processor and the I2C devices only ever pull the bus low. The bidirectional bus is implemented using open-collector drivers. Fortunately, you rarely need one, as describe below. That's a detail you won't generally have to worry about that's taken care of by the Photon/Electron I2C hardware and your I2C device automatically.īut this means you can't use a plain level-shifter, for example, on an I2C bus. The SCL (clock) line is mostly generated by the processor (Photon/Electron), though it too is somewhat bidirectional when clock stretching is used. The I2C protocol determines which direction data will be sent. The SDA (data) line is used to send data both to and from the I2C devices. That has an addressable bus as well, but it has a 64-bit address and each sensor device has a unique serial number from the factory, with no hardware configuration needed. It's also different than the 1-Wire interface used by the DS18B20 temperature sensors. So if you want to connect four SPI devices to a SPI bus, you need to dedicate four separate GPIO pins for the select lines, one for each of for the SPI devices. This is different than SPI, which is also a bus, but uses a device select line (called variously SS, CS, EN, etc.) for each device. This sub-address is typically set using jumpers, solder pads, or switches. For the DS75 temperature sensor, it's eight. Sometimes there can be conflicts, which limit the ability to share the I2C bus.Īlso, there may be limits the number of identical I2C devices you can have on an I2C bus. One difficulty is that the address is only 7 bits, so there are 128 addresses. It's an addressable busĮach I2C device on the bus has an address, which uniquely identifies which device the processor wants to communicate with. In I2C terminology, the Photon/Electron is the I2C Master device, and all of the other devices (sensors, displays, etc.) are I2C Slave devices. The regular version of I2C described here is designed for short distances, up to a few meters, preferably less. ![]() Most devices also require power and ground, so generally 4 wires are needed. The communication requires two lines, SDA and SCL. This is different than the serial ports, for example, which generally connected only two devices together. There are some limitations to this, which we'll go into details later. That means there can be multiple I2C devices connected to a single port on the Photon/Electron. The second section has some examples of I2C devices that work with the Photon and Electron and some sample code. The first section has some technical information about how it works and why you might want to use it. **************************************** Include Libraries ***************************************/ #include "Ubidots.I2C, also written as I 2C, and pronounced I-squared-C, is a method for communicating between devices such as sensors, displays and other peripherals and a microcontroller like the Photon or Electron. This example sends data to a variable to // Ubidots using Particle Webhooks. For additional details about connecting your Particle devices to Ubidots, be sure to check out Connect a Particle Device to Ubidots. In this tutorial we will explain how to interact with Ubidots REST API using Particle's Cloud and webhooks. ![]() ![]() Or as Particle says: "Webhooks bridge the gap between the physical and the digital world, helping you get your data where you need it to be". For example, you can connect a motion sensor to a device and have the recorded data trigger an event whenever motion is detected. Webhooks allow a device to generate an event based on a condition or variable values. To integrate your Particle device's data into your Powered by Ubidots App, a webhook will be used to bridge the Particle cloud with Ubidots. They combine an ARM micro-controller, a communication chip (WiFi, GPRS or 3G) and a web IDE with tons of community examples and libraries to get started quickly. Particle devices are compact and easy-to-code hardware development kits that provide everything you need to build cloud-connected solutions. ![]()
0 Comments
Leave a Reply. |