4.0. Introduction Serial communications provide an easy and flexible way for your Arduino board to interact with your computer and other devices. This chapter explains how to send and receive information using this capability. Described how to connect the Arduino serial port to your computer to upload sketches. The upload process sends data from your computer to Arduino and Arduino sends status messages back to the computer to confirm the transfer is working. The recipes here show how you can use this communication link to send and receive any information between Arduino and your computer or another serial device. Figure 4-1. Arduino Serial Monitor screen You can also send data from the Serial Monitor to Arduino by entering text in the text box to the left of the Send button. Baud rate is selected using the drop-down box on the bottom right. Msde 2000 sp4 download. UART: This is the number of separate serial communication lines your Arduino board can support. On most Arduino boards, digital I/O pins 0&1 double as your serial send and receive pins and are shared with the serial programming port. Some Arduino boards have multiple UARTs and can support multiple serial ports at once. By John Nussey. The only thing better than sending signals to Processing is sending multiple signals, right? Sending multiple signals is often a stumbling block, though, because although sending values from multiple sensors is easy, handling them in the correct order on the other end can often be difficult. Arduino Multiple Software Serial Ports And CablesYou can use the drop down labeled “No line ending” to automatically send a carriage return or a combination of a carriage return and a line at the end of each message sent when clicking the Send button. Your Arduino sketch can use the serial port to indirectly access (usually via a proxy program written in a language like Processing) all the resources (memory, screen, keyboard, mouse, network connectivity, etc.) that your computer has. Your computer can also use the serial link to interact with sensors or other devices connected to Arduino. Implementing serial communications involves hardware and software. The hardware provides the electrical signaling between Arduino and the device it is talking to. The software uses the hardware to send bytes or bits that the connected hardware understands. The Arduino serial libraries insulate you from most of the hardware complexity, but it is helpful for you to understand the basics, especially if you need to troubleshoot any difficulties with serial communications in your projects. Note Using 0 volts (for 0) and 5 volts (for 1) is very common. This is referred to as the TTL level because that was how signals were represented in one of the first implementations of digital logic, called Transistor-Transistor Logic (TTL). Boards including the Uno, Duemilanove, Diecimila, Nano, and Mega have a chip to convert the hardware serial port on the Arduino chip to Universal Serial Bus (USB) for connection to the hardware serial port. Other boards, such as the Mini, Pro, Pro Mini, Boarduino, Sanguino, and Modern Device Bare Bones Board, do not have USB support and require an adapter for connecting to your computer that converts TTL to USB. See for more details on these boards. Some popular USB adapters include. • Mini USB Adapter () • FTDI USB TTL Adapter () • Modern Device USB BUB board () Some serial devices use the RS-232 standard for serial connection. These usually have a nine-pin connector, and an adapter is required to use them with the Arduino. RS-232 is an old and venerated communications protocol that uses voltage levels not compatible with Arduino digital pins. You can buy Arduino boards that are built for RS-232 signal levels, such as the Freeduino Serial v2.0 (). RS-232 adapters that connect RS-232 signals to Arduino 5V (or 3.3V) pins include the following. • RS-232 to TTL 3V-5.5V adapter () • P4 RS232 to TTL Serial Adapter Kits () • RS232 Shifter SMD () A standard Arduino has a single hardware serial port, but serial communication is also possible using software libraries to emulate additional ports (communication channels) to provide connectivity to more than one device. Software serial requires a lot of help from the Arduino controller to send and receive data, so it’s not as fast or efficient as hardware serial. The Arduino Mega has four hardware serial ports that can communicate with up to four different serial devices. Only one of these has a USB adapter built in (you could wire a USB-TTL adapter to any of the other serial ports). Shows the port names and pins used for all of the Mega serial ports. Software Serial You will usually use the built-in Arduino serial library to communicate with the hardware serial ports. Serial libraries simplify the use of the serial ports by insulating you from hardware complexities. Sometimes you need more serial ports than the number of hardware serial ports available.
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