Serial Communication Examples

This tutorial (originally published here) demonstrates how to use a Raspberry Pi Pico as a live-data source in LabPlot via serial communication. The examples show how to stream real-time data from a microcontroller to create live updating plots.

Note

While these examples were created in collaboration with the core LabPlot developer team, they do not reflect in any way the thoughts or intentions of any of the LabPlot developers.

Prerequisites

Hardware Requirements

• Raspberry Pi Pico or compatible microcontroller

• USB cable for connection to your computer

• Computer running Linux, Windows, or macOS

Software Requirements

• LabPlot (version 2.10 or later recommended)

• PlatformIO for code compilation (using Arduino framework)

• Terminal emulator for testing:

  • Linux: Picocom

  • Windows: PuTTY

  • macOS: Built-in terminal or similar

Important

On Linux systems, make sure to follow PlatformIO’s documentation to install the appropriate udev rules so your Pico shows up as a tty device.

Code Configuration

The example Pico code includes several configurable parameters at the top of the source file:

// ----------------------------------------------------------------------------
//  Parameters
// ----------------------------------------------------------------------------
#define BAUDRATE  9600   // Serial baudrate
#define SEPERATOR ","    // Seperator between multiple ASCII values in multiASCII mode
#define INTERVAL  1000.0 // Send interval in milliseconds

// Mode, choose one.
enum mode {
  singleASCII,  // --> One ASCII value every INTERVAL. No Newline or seperator. 9 decimals.
  multiASCII,   // --> ASCII CSV of several values every INTERVAL. separated by SEPERATOR. 9 decimals.
  singleBinay,  // --> One binary value every INTERVAL. Formatted TODO
  multiBinary   // --> Several binary values every INTERVAL. Formatted TODO
};

const uint8_t mode = singleASCII;

Default Settings

• Baudrate: 9600 bps

• Send interval: 1000 ms (1 second)

• Mode: Single ASCII value

• Decimal precision: 9 digits

Uploading Code to the Pico

First Upload (Manual Process)

The very first time you connect the Pico to your PC, it will appear as a mass storage device and won’t accept serial uploads through PlatformIO. Follow these steps for the initial upload:

1. Build the project in PlatformIO using the “Build” task

Execute the Build Project Task in PlatformIO

2. Locate the firmware file: Find the generated firmware.uf2 file in PlatformIO’s build directory

Location of the generated firmware.uf2 file in PlatformIO’s build directory

3. Copy to Pico: Drag and drop firmware.uf2 to your Pico (it appears as a USB flash drive)

4. Restart: Power cycle your Pico by unplugging and plugging it back in

Tip

Subsequent code uploads are much easier, as PlatformIO should automatically detect your Pico when executing upload tasks. Only the first upload needs to be done manually.

Identifying the Serial Port

Linux

When your Pico is connected, it will appear as a tty device. To find it:

# Check system messages for new USB devices
sudo dmesg

# List all tty devices
ls /dev/tty*

The Pico typically appears as /dev/ttyACM0 or similar.

Output of sudo dmesg right after plugging in the Pico:

Output of sudo dmesg showing the Pico connecting as ttyACM0

Output of ls /dev/tty*:

Available tty devices showing the connected Pico

Windows

On Windows, the device will appear as a COM port (e.g., COM3, COM4). Check Device Manager to identify the correct port.

macOS

Use the terminal to list available devices:

ls /dev/tty.*

Testing Serial Communication

Before setting up LabPlot, test the serial connection using a terminal emulator:

Linux Example

Using Picocom:

picocom -b 9600 /dev/ttyACM0

Windows Example

Use PuTTY with the following settings:

• Connection type: Serial

• Serial line: COM3 (or your identified port)

• Speed: 9600

Example 1: Single Value ASCII

Configuration

Set the mode in your Pico code to:

const uint8_t mode = singleASCII;

This mode sends a single ASCII value every INTERVAL milliseconds, ending with \r\n.

Expected Output

When connected via terminal, you should see output like:

1.000000000
0.951056540
0.809017003
0.587785244
0.309017003
0.000000000
-0.309017003
-0.587785244
-0.809017003
-0.951056540
-1.000000000

This represents a sine wave with values calculated by the microcontroller.

Setting up LabPlot Live Data Source

1. Add Live Data Source: In LabPlot, go to the menu and add a new live data source

Adding a new Live Data Source in LabPlot

2. Configure Serial Settings:

   • Source Type: Select “Serial Port”

   • Serial Port: Choose your identified port (e.g., /dev/ttyACM0)

   • Baudrate: Set to 9600 (matching your code configuration)

   • Update Interval: Set to match your INTERVAL setting (1000 ms by default)

3. Data Format Settings:

   • Data Format: ASCII

   • Column Separator: Not applicable for single values

   • Create Timestamp: Enable if desired

   • Create Index: Enable if desired

4. Apply Custom Filter: Configure any necessary data filtering

Live Data Source configuration settings for serial communication

Result

After accepting the settings, you should see your live data source updating every interval with new data. The spreadsheet will show:

• The received sine wave values

• Timestamps (if enabled)

• Index numbers (if enabled)

Live Data Source showing updating values with timestamps and index

Creating a Live Plot

1. Create a new worksheet and add an XY-curve

2. Set the data source to your live data source

3. Configure X-axis to use timestamps or index

4. Configure Y-axis to use your data values

5. The plot will show a live-updating sine wave

Live updating sine wave plot showing real-time data from the Pico

Example 2: Multi Value ASCII

Configuration

For sending multiple values simultaneously, set:

const uint8_t mode = multiASCII;

This mode sends multiple ASCII values separated by the defined SEPERATOR (comma by default).

Expected Output

The serial output will contain multiple comma-separated values per line:

1.000000000,0.500000000,0.250000000,0.125000000
0.951056540,0.475528270,0.237764135,0.118882068
0.809017003,0.404508502,0.202254251,0.101127125

Example of multi-value ASCII output showing multiple data streams

Setting up Multi-Value Live Data Source

The configuration is similar to single values, but with these differences:

• Column Separator: Set to comma (,) or your chosen separator

• Multiple Columns: LabPlot will automatically create separate columns for each value

This allows you to plot multiple data streams simultaneously, each updating in real-time.

Troubleshooting

Common Issues

Port Access Denied (Linux)

Install udev rules as mentioned in prerequisites, or run with sudo (not recommended for regular use).

No Data Received

• Verify baudrate matches between Pico code and LabPlot settings

• Check that the correct serial port is selected

• Ensure the Pico is running the correct firmware

Irregular Updates

• Match the update interval in LabPlot exactly to your Pico’s send interval

• This requirement may change in future LabPlot versions

Connection Lost

• Check USB cable connection

• Verify the Pico hasn’t reset or changed ports

• Restart the live data source in LabPlot

Tips for Success

1. Test First: Always test serial communication with a terminal emulator before configuring LabPlot

2. Match Settings: Ensure baudrate and timing match between all components

3. Start Simple: Begin with single value ASCII mode before attempting multi-value streams

4. Monitor Resources: Live data can consume memory over time; consider data limits for long-running sessions

Advanced Applications

The serial communication examples can be extended for various real-world applications:

• Sensor Monitoring: Stream data from temperature, humidity, or pressure sensors

• Motor Control Feedback: Monitor speed, position, or current from motor controllers

• Environmental Monitoring: Collect and visualize environmental data in real-time

• Prototype Testing: Validate embedded system behavior during development

Further Resources

• Original GitHub Repository

• LabPlot Official Documentation

• PlatformIO Documentation

• Raspberry Pi Pico Documentation

Contributing

If you have improvements or additional examples for serial communication with LabPlot, consider contributing to the original repository or sharing your experiences with the LabPlot community.

License

The original examples are licensed under GPLv3.

Acknowledgments

This tutorial is based on work by Chrismettal and was created in collaboration with the LabPlot development team.

• If you enjoy this tutorial, consider supporting the original author

• If you use LabPlot regularly, consider supporting LabPlot’s developers