The master is the controlling device (usually a microcontroller), while the slave (usually a sensor, display, or memory chip) takes instruction from the master. Start and stop conditions define the beginning and end of each packet, so the data is interrupted during transmission.ĭevices communicating via SPI are in a master-slave relationship. With I2C and UART, data is sent in packets, limited to a specific number of bits. Any number of bits can be sent or received in a continuous stream. One unique benefit of SPI is the fact that data can be transferred without interruption. For example, SD card reader modules, RFID card reader modules, and 2.4 GHz wireless transmitter/receivers all use SPI to communicate with microcontrollers. SPI is a common communication protocol used by many different devices.
#Spb protocol serial#
The following diagram shows the serial transmission of the letter “C” in binary (01000011): In serial communication, the bits are sent one by one through a single wire. In parallel communication, the bits of data are sent all at the same time, each through a separate wire. The following diagram shows the parallel transmission of the letter “C” in binary (01000011):
The bits of data can be transmitted either in parallel or serial form. In a system operating at 5 V, a 0 bit is communicated as a short pulse of 0 V, and a 1 bit is communicated by a short pulse of 5 V. Bits are transferred from one device to another by quick changes in voltage. A bit is like a letter in a word, except instead of the 26 letters (in the English alphabet), a bit is binary and can only be a 1 or 0. Parallel CommunicationĮlectronic devices talk to each other by sending bits of data through wires physically connected between devices. SPI, I2C, and UART are quite a bit slower than protocols like USB, ethernet, Bluetooth, and WiFi, but they’re a lot more simple and use less hardware and system resources. SPI, I2C, and UART are ideal for communication between microcontrollers and between microcontrollers and sensors where large amounts of high speed data don’t need to be transferred. In the next article, we’ll discuss UART driven communication, and in the third article, we’ll dive into I2C.
In this series of articles, we will discuss the basics of the three most common protocols: Serial Peripheral Interface (SPI), Inter-Integrated Circuit (I2C), and Universal Asynchronous Receiver/Transmitter (UART) driven communication.įirst, we’ll begin with some basic concepts about electronic communication, then explain in detail how SPI works. Luckily for us, there are only a few communication protocols we need to know when building most DIY electronics projects. In electronics, these languages are called communication protocols. Both sides need to speak the same language. Communication between electronic devices is like communication between humans.
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