Serial processing serial#
Serial processing code#
Serial processing plus#

There is no data type for strings in the C language. In the code, I use C language strings - that is an array of chars. The program expects the commands to be terminated by Return key (carriage return char).

Serial processing serial#

Important Note: When you test the program in Arduino Serial Monitor, set it to send the Carriage Return characted in the bottom of the window instead of the default No line ending.

Serial processing code#

The code doesn't make any assumptions such as that the program will be always receiving characters when the user starts to type. The commands can be up to MAX_DATA_LEN chars long and they are received in a way which does not block the loop() function. The first example processes commands from the user. So here, I present a solution which should be able to handle the characters coming in random times and process the commands or data when it is really ready without blocking the loop for long time. Anyway, I am sure you want your program to be robust and handle all the situations nicely. So the data on the serial line come in short bursts like “ command1 command2” instead of “ c o m m a n d 1 c o m “ etc., which will happen if the chars are sent immediately after the user types them – which is what normal terminal programs do. Note: The Serial Monitor in Arduino IDE may somehow hide these problems because it lets the user type the whole string (command) and then send it by the Send button.

Serial processing plus#

Plus you probably don’t want to limit the commands to fixed length. There may be invalid commands, random spaces between each char, etc. The situation may be even worse if the sender is a person rather than another Arduino. For example, the first char it receives may be “ 2”, and then the condition if (Serial.available() = 3) will be true when we receive ' 200' instead of ' 002' or ' 003' – invalid number. It may start receiving at any random position in the sequence. But imagine, for example, that the receiving Arduino is powered off and then back on. Now if the receiving program is “in sync” – if it starts reading from the beginning, it will receive the numbers all right. Here is what the sequence of chars coming from the serial line could look like: Our program in another Arduino is receiving the numbers and it needs to run its loop 10 times per seconds to control the nuclear reactor in your basement. Suppose one Arduino is sending numbers (fixed 3 digits length) once per second. In this code, I assume that the data/command are 3 chars long and I only do the processing if there are exactly 3 characters received. But you cannot stop your loop and wait! You want to keep processing the inputs and controlling outputs 10 times per second – imagine your program controls a quadrocopter it cannot just stop controlling the aircraft and wait for the data to arrive from serial line.Īnother solution is to change the condition to something like this: One solution would be to wait for all data to come something like calling Serial.readStringUntil which will read until a terminator character is received or there is a timeout. There may be just the first char, or the first two chars, etc.

If your data or command is more than 1 char long, there is a good chance that you cannot process it yet because it is not completely received. The condition is true if there are one or more characters available. Well, you put if (Serial.available() > 0) into your loop and if there are some data (or command), you process it. Now you want your program to respond to commands sent from the serial line or to process data sent from another Arduino. You make your loop code run fast, for example, it is executed 10 times per second. You have a program which is doing lot of things – reads the sensors, controls outputs, shows current status on a display, etc. Let me explain what I mean by an example. It may seem easy but often you run into problems. When writing Arduino programs, you sometimes need to receive some commands or data from serial line.