Arduino Serial Stx Etx [PORTABLE]
I would like to collect and print correctly information received from a serial device. I have an Arduino Mega, then, I've connected the TX/RX pins to the serial device (only one TX and one RX) using the Serial2.
Arduino Serial Stx Etx
are you porting this code from another device ?are you sure you have the Tx and Rx lines connected correctly?I tend to use Serial1 on the Megapin 18 is the serial transmit from the arduino, i.e. Serial1.print()pin 19 is the serial receive, i.e. Serial1.read()
A difference between the methods in the serial input basics tutorial and readBytesUntil() is that readBytesUntil blocks while reading serial and the serial input basics methods do not. It may be the difference between a responsive program and one the seems to lag. Serial input is slow in terms of the Arduino processor. With the serial input basics methods the Arduino can do thousands of things instead of being tied up waiting for serial input.
There's a huge difference between "blocking" while copying data from a dedicated serial buffer to an array controlled by your code and blocking while you're waiting for data to come in through the serial port. The former takes microseconds to copy data that's already in the buffer. The latter takes an indeterminate amount of time.
i was looking at this strtok() aswell, and i realy like the idea of splitting the data string up and placing it in an array, it would make it neater when i eventually add more sensors, so that i could just add each sensor reading to the same array. then at the end of the loop, put all the relevant readings into 1 serial print.
but i cant seem to wrap my head around this function at the moment, i am still quite new with this programming, the arduino code in general i can read my way out of, and it sorta makes sense. serial.read - reads what is on the serial port. but this strtok doesnt make much sense, i assume it's in C or something like that. maybe when i get a bit more experience in programming it makes more sense.
this project did sound fairly simple at the beginning, but it would seem that i have underestimated the complexity of the matter, and starting out with a fairly advanced sensor and including RS485, arduino, raspberry and a web server in my first project, might be a bit of a large project to start with. but i guess i have to challenge myself in order to learn but 1 step at a time.
frichsness:but i cant seem to wrap my head around this function at the moment, i am still quite new with this programming, the arduino code in general i can read my way out of, and it sorta makes sense. serial.read - reads what is on the serial port. but this strtok doesnt make much sense, i assume it's in C or something like that. maybe when i get a bit more experience in programming it makes more sense.
The nice thing about those examples is that is really easy to get them to run on the arduinoabout the only things to do is to remove the #includes at the top, place the code which is in main() into setup() and replace printf( " %s\n", xxx ); with Serial.println(xxx); (err.. don't forget to set up serial in the first place )That way you can play with the strings and tokens and see the results, rather than just reading about them.
Be aware, the arduino framework does not have printf() by default. it adds a lot to the code size.However, it does have sprintf(). sprintf() will let you output to a C string (character array) with formatting, which you can then use Serial.println() to print to the serial port. eg:
I put a Serial.print(serialInByte); in front of the *command = *command + serialInByte; and this prints out the correct input. So what's read seems not to be the problem. After the line I put Serial.print(&command); but the compiler gives me the error "call of overloaded 'print(String**)' is ambiguous" here. I think there is something wrong with the command variable?
I'm looking at other threads that might provide a clue. In my flow, I have one serial output node (to send test messages to the serial port) and then a separate serial input node to see the responses. I will look into using the serial request node, but I wanted to separate them for now to play around with Node-RED.
This is really driving me crazy... The first settings work every single time without fail and the data is exactly the same in the debug window. I'm using my [Turn Off] injector to send data into the serial port for my testing. I've also monitored the serial port myself (minicom, etc) and the data input/output is exactly the same so I'm not sure why the start character is acting so inconsistently?
Going forward, it looks like I should use the serial request node though, right? For example, I need to send a serial command and wait for an acknowledge response. (I was using Serial In and Serial Out to learn Node-RED and test the commands individually, etc)
The function receiveMessage reads from the serial port, discarding all characters until it receives a STX. Once the STX is received it reads characters, adding them to the message buffer and calculating the check-sum. If an ETX is received, it assumes the next character is the check-sum. Once the check-sum is received, it compares it with the calculated check-sum; if the two check-sums do not match, the message is discarded.
The serial monitor provides a convenient way for showing serial communication between the Arduino boards and the Computer. However, it does not allow the computer to react according to the value received. No worry, you can write your own Serial Monitor using Python! pySerial is a Library which allows python programs to access the serial port. Thus, we can now bridge Arduino board and the computer by ourselves.
Copy the following 2 programs as 2 separate files. change the line ser = serial.Serial('/dev/ttyACM0', 9600) according to the port name of Arduino in your OS. It should be something like /dev/ttyACM0.
A serial port cannot be opened twice on Windows. Therefore, we have to use a multi-thread version. Copy the following program and save it as a file. change the line ser = serial.Serial('COM3', 9600) according to the port name of the Arduino in your OS. It should be something like COM4.
It is possible to configure the UniStream PLCs to talk to 3rd party devices such as: frequency converters, RFID cards readers, bar-code readers, and printers with as long as they have proprietary protocol over serial RS232/RS485 or TCP/IP and you know the structure of this protocol.
So what I want to know is how the software reading from the serial interface will know that a packet has ended; One way I thought is by sending an EOF byte but I am afraid of "rogue" EOF values in packet data.
This will just short of double the amount of data you have to move, but do so in a very simple and deterministic way, and you can crank up the serial baud rate to handle it, especially as the baud rate only actually "exists" between two ATmega chips within the Uno.
Most serial protocols use certain characters to indicate certain things, and indeed the ASCII character set has certain characters earmarked for certain jobs in communication, so it makes sens to use those.
A serial interface is used for information exchange between computers and peripheral devices. When using a serial communication, the information is sent bit by bit (serial) over a cable. Modern serial interfaces are Ethernet, Firewire, USB, CAN-Bus or RS-485 even though they are not always called "a serial interface". The principle stays the same: Information is bit-by-bit transformed over short distances. Glenn Patton published a great article about the design patterns used by serial communication Ports - It is available on CodeProject.
Now, in order to focus on the serial communication, I decided to leave out the EEPROM reading/writing and just define a set of dummy values which are sent whenever a request for the temperature data is coming to the Arduino board. I did a quick example of how a single set of data will look in the Arduino C++ code (I use Arduino's String class):
I will not go into detail about the thermometer implementation since there are plenty of instruction sets on how to build one available on the internet - We are going to send dummy values anywaysHowever, the Arduino board may receive a serial command telling it to read the collected temperature data. I assigned every command a single command code, and defined it to be terminated by a '#' character. So for example, the command to tell the Arduino board has to send the stored temperature data would come like this over the serial interface of the Arduino board, issued by the .NET application which is going to display the temperature data:
Simples. That's it. After the Arduino Board receives this command, it is going to send our previously defined dummy data up to the .NET application, using the serial port, too (Of course, this requires the .NET application to stop sending any command down to the Arduino board):
I created a method which reads a command from the Arduino Board's serial input buffer and writes it into the pointer which points to an Arduino-String - returned is an integer value indicating an operation success or an operation fail / warning. It returns either one of the three following codes:
The default return code operationStatus is MSG_METHOD_SUCCESS. If no data is available in the serial input buffer (checked by calling Serial.Available() which returns true if there is data in the serial input buffer), the said operationStatus has the code WRG_NO_SERIAL_DATA_AVAILABLE assigned.
What now happens is not a big deal and easy to explain. I declared the variable serialInByte in order to store a single byte which was read by the Serial.Read() method (which reads exactly one byte from the serial input buffer). I call the said Serial.Read() method, store the byte returned into serialInByte and append serialInByte to the command pointer - This goes on and on until no data is available in the serial input buffer, or the character "#" is showing up, indicating the end of a command. 350c69d7ab
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