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SERIAL PORT, GPSThe source code of all examples can be downloaded from.What is the RS-232C protocol?Although Bluetooth, Ethernet, or USB interfaces are commonly used for communication between a computer and peripherals (and I 2C, SPI and 1-Wire for microcontroller systems), the communication over the serial interface (RS-232C) is still widespread. Traditionally the serial interface is still used to connect measurement devices (voltmeters, oscilloscopes, etc.) and to communicate with roboters, modems and microprocessor systems (e.g. Downloading programs to the Arduino).
/Programming in C/C / UART Serial Port / Using the UART. If you are running Raspbian or similar then the UART will be used as a serial console. We will use the serial port available on Raspberry with a RS232/TTL 3-5,5V adapter and a USB-serial adapter. By default the Raspberry Pi’s serial port is configured to be used for console input/output. This can help to fix problems during boot, or to log in to the Pi if the video and network are not available. To be able to use the serial port to connect and talk to other devices (e.g. A modem a printer.
Modern computers no longer have serial ports, however this problem can be easily solved with low cost USB-to-serial adapters.The format of the transmitted data is simple. It consists of chronologically transmitted data bytes. The transfer begins with a start bit, where the receiver calls attention to the pending data transfer.
Then the data itself follows, including 5, 6, 7 or (usually) 8 bits. In order to facilitate an error correction, a parity bit may be sent which indicates whether an odd or an even number of bits were set, but the parity bit may also be omitted. The transfer is completed with one or two stop bits. In the idle state the sending and receiving devices are not synchronized with each other, i.e. The data transfer can begin at any time (asynchronous protocol). However, it is necessary that both devices agree upon the same time duration of a single bit. This is specified by the baud rate (in baud, bits/s) and can usually only be any of the standardized values 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 115200 baud.
In addition, both devices can agree on a handshake (flow control), with which they inform each other whether they are ready for the data transfer. # Serial1.py import serialimport timeport = '/dev/ttyAMA0' # Raspberry Pi 2 #port = '/dev/ttyS0' # Raspberry Pi 3 def readLine(port):s = ' while True:ch = port.reads += chif ch 'r':return sser = serial.Serial(port, baudrate = 1200)print 'starting' while True:time.sleep(1)print 'sending synch'ser.write( 'A')rcv = readLine(ser)print 'received:', rcv(Ctrl+C copy, Ctrl+V paste)Remarks:The Raspberry Pi controller sends a synchronizing character 'A' to the device to request data. Then it accumulates incoming characters in the blocking function readLine until a is received.To avoid blocking the main loop may request data every second and accumulate any number of received characters by checking the number of characters nbChars in the input buffer and use read(nbChars) to get them altogether.Program. # Serial2.py import serialimport timeport = '/dev/ttyAMA0' # Raspberry Pi 2 #port = '/dev/ttyS0' # Raspberry Pi 3ser = serial.Serial(port, baudrate = 1200)print 'starting' while True:time.sleep(1)ser.write( 'A')nbChars = ser.inWaitingif nbChars 0:data = ser.read(nbChars)print data(Ctrl+C copy, Ctrl+V paste)Remarks:For testing purposes of a RS-232 device attached to the Raspberry Pi, it is sometime convenient to use a terminal emulator in order to communicate manually instead of using a program. To do so, install PuTTY on the Raspberry Pi with the commandsudo apt-get install puttyand open PuTTY in an VNC session by clicking the icon in Menu Internet. In the Basic options dialog check the button Serial and select /dev/ttyS0 for the Raspberry Pi 3 or /dev/ttyAMA0 for older versions.Experiment 2: Use a GPS module and show current GPS informationCommercial GPS modules are typical devices that use the serial protocol to transmit data to an external device.
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Most of them do not require any special setup nor commands to function. When powered up, they send lines of ASCII text in a special format, called messages, that can be received as string with with a simple readline call. Normally the baud rate is 9600 baud by default, but you should consult the data sheet to check this.Aim:Attach a GPS module to the Raspberry Pi and capture data lines in the console. The module mounted on a Raspberry Pi breakout board with a 40 pin header. It is more sophisticated and contains a real-time clock with battery backup and a 3 axis digital compass using I 2C communication. It is available from different distributors (see also on eBay). Download game inazuma eleven strikers 2012 xtreme pc.
Connecting the module is extremely simple, just use 3 wires as shown in the picture here. If you are operating the module outdoor, there is no need for an external antenna. To test the module, you can start a PuTTY terminal (baud rate: 9600 baud) in a VNC session or write a simple Python program that just reads and displays the incoming data. Be aware that for the Raspberry Pi 3 the serial port name is different and you must set the corefreq parameter as stated above.Do not power the module with 5V! # Serial3.py import serialport = '/dev/ttyAMA0' # Raspberry Pi 2 #port = '/dev/ttyS0' # Raspberry Pi 3ser = serial.Serial(port, baudrate = 9600, timeout = 0.5)while True:data = ser.readlineprint 'Data:-', data,(Ctrl+C copy, Ctrl+V paste)Remarks:The NMEA protocol is somewhat knotty. All NMEA messages start with the $ character, and each data field is separated by a comma.
The line containing the latitude and longitude of the current location can be extracted in the $GPGGA line that contains 14 fields. Follows an example: $GPGGA,1819.7041778,N,270,W,4,13,1.00,495.144,M,29.200,M,0.10,0000.40GP represent that it is a GPS position (GL would denote GLONASS).181908.00 is the time stamp: UTC time in hours, minutes and seconds.34 is the latitude in the DDMM.MMMMM format. Decimal places are variable.N denotes north latitude.270 is the longitude in the DDDMM.MMMMM format. Decimal places are variable.W denotes west longitude.4 denotes the Quality Indicator:0 = No GPS data1 = Uncorrected coordinate2 = Differentially correct coordinate (e.g., WAAS, DGPS)4 = RTK Fix coordinate (centimeter precision)5 = RTK Float (decimeter precision.13 denotes number of satellites used in the coordinate.1.0 denotes the HDOP (horizontal dilution of precision).495.144 denotes altitude of the antenna.M denotes units of altitude (eg. Meters or Feet)29.200 denotes the geoidal separation (subtract this from the altitude of the antenna to arrive at the Height Above Ellipsoid (HAE).M denotes the units used by the geoidal separation.1.0 denotes the age of the correction (if any).0000 denotes the correction station ID (if any).40 denotes the checksum.Here a proposal how to parse the line 'hand-knitted':Program.
In this tutorial I’ll show you how to communicate between a Raspberry Pi and an Arduino board via Serial communication.First, I’ll quickly explain what is Serial communication. Then you’ll see how to setup your hardware and software, and we’ll dive into the Python code (Cpp for Arduino). A basic example at first, leading to a more complete application using a Raspberry Pi, an Arduino, and other electronic devices.This tutorial will work with a Raspberry Pi 4 (and earlier: 3B, 3B+) board, and any Arduino board. I’ll use mostly Arduino Uno but will give more details about the differences between Arduino boards when it comes to Serial communication.When working with electronic devices, communication is key. Each device – on top of doing well what it’s supposed to do – must be able to clearly communicate with other devices.
That’s one of the most important thing to work on in order to switch from a very basic application to more complex ones.
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