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Flashing a Pico for USB

This guide will walk you through compiling and flashing Klipper firmware on a USB Pico board. This process will work for any RP2040-based boards.

However, some steps such as putting the board into flashing mode may differ slightly between models.

header

Compiling the firmware

Run the following:

cd ~/klipper
make menuconfig

Use this configuration for a usb-connected Pico board:

USB Pico menuconfig

Match those settings, and then press q

Press y to save changes.

Now run:

make

This will take a moment, and once complete it will spit out a klipper.u2f file in ~/klipper/out

Now we need to put the board into flashing mode.

This is typically performed by holding the boot button while connecting the board to USB.

Flashing the firmware

You can now try to run the following command:

sudo mount /dev/sda1 /mnt

If putting the Pico into flash-mode was unsuccessful, it won't show up as a mountable storage device.

If you have other external storage devices the sda1 part may be different.

You can use the following command to see all the available storage devices:

sudo fdisk -l

Match your Pico with the correct /dev/sda# address and modify the mount command as necessary.

When you have successfully mounted the storage there will be no feedback or errors from the mount command.

You can test it by running:

ls /mnt

The storage should contain a couple of files:

  1. INDEX.HTM
  2. INFO_UF2.TXT

If the ls command returns those, you are ready to flash!

Run the following command:

sudo cp out/klipper.uf2 /mnt

This will copy the firmware image we compiled earlier onto the Pico's storage and it will be flashed automatically.

This may take a minute or so.

When it is complete, the storage will be automatically unmounted.

I like to repeatedly run the ls /mnt command until it stops listing the files. That indicates the flash is now complete.

Retrieving the ID

You can now run the ls /dev/serial/by-id/* command and if the flash was successful it should list a serial ID for the Pico.

An RP2040 ID will look something like this:

usb-Klipper_rp2040_E660C063145C6B24-if00

A properly flashed Klipper firmware will have Klipper_rp2040 in the ID.

If no ID is shown, try disconnecting the Pico from USB and reconnecting it before running the command again.

If it still fails to list an ID, then you may have missed a step and should go back and repeat all of the previous steps until the flash is successful.

Configuring Klipper

Once you have successfully compiled and flashed the firmware and retrieved the serial ID, we are now ready to configure Klipper.

This is the easy part.

In your printer.cfg file, add the following:

[mcu my_pico]
serial: /dev/serial/by-id/usb-Klipper_rp2040_E660C062135C6A24-if00

Remember to change the usb-Klipper_rp2040_E660C063145C6B24-if00 to your board's unique ID.

You can name it however you'd like.

In this example we will use my_pico but any name is acceptable.

Just remember to use that same name when referencing the mcu/pins in other configuration sections.

That's it!

Presumably you'd like to add additional components, but I would suggest starting out with just this most basic pico mcu configuration to ensure Klipper is able to connect successfully.

If you are able to successfully start/connect Klipper with that section added to your printer.cfg file, you are done!

You can now try adding some extras as described below:

Adding an accelerometer

You can wire up an accelerometer like an ADXL345 to a Pico for use in Klipper.

Here is an example:

[adxl345 my_accel]
cs_pin: my_pico: gpio1
spi_software_sclk_pin: my_pico: gpio2
spi_software_mosi_pin: my_pico: gpio3
spi_software_miso_pin: my_pico: gpio4

Then you just wire up the corresponding pins on the accelerometer to the gpio pins. The pins you use may be different depending on the model of Pico you have.

I try to use the existing SPI bus, but as shown in the example above, you can just specify the pins you want to use and it doesn't matter what their original purpose was.

If you only have the one accelerometer, you do not need to name it. You can just use:

[adxl345]

instead of:

[adxl345 my_accel]

You will then need to add a resonance_tester section.

If you have multiple accelerometers that will look something like this:

[resonance_tester]
accel_chip_x: adxl345 my_other_accel
accel_chip_y: adxl345 my_accel
probe_points:
    100,100,20 # an example

If you have only a single accelerometer, it will look more like this:

[resonance_tester]
accel_chip: adxl345
probe_points:
    100,100,20 # an example

The probe_points value is the X,Y,Z coordinates where you would like the test to occur. You can also test in multiple locations by adding additional coordinates on a new line below. For example:

probe_points:
    100,100,20 # an example
    50,50,100  # another example

This is a fantastic resource if you want more information on setting up an accelerometer.

Useful Extras

MCU Core Temperature

Configure MCU Core Temperature

We can have Klipper read the core temperature from the Pico to monitor it.

This is a built-in sensor that is present on all RP2040 chips.

To do that, simply add the following to your printer.cfg file:

[temperature_sensor pico_temp]
sensor_type: temperature_mcu
sensor_mcu: my_pico
min_temp: 0
max_temp: 100

Note that we are using my_pico for the sensor_mcu

As with the mcu itself, we can name the temperature sensor however we'd like.

Some helpful guidelines:

pico_temp will typically display as Pico Temp in most interfaces (Mainsail, Fluidd, KlipperScreen, etc)

_pico_temp will be hidden from the user interface in Mainsail and KlipperScreen (but not Fluidd)

Putting an underscore at the start of the name can be used to create components that are controllable/readable from macros, but not from the UI. This works with macros, fans, sensors, heaters, output_pins, etc.

Using MCU Core Temperature

We can reference the current core temperature in macros using the following method:

First we create a shortcut allowing us to use core_temp to reference the value in our macro:

{% set core_temp = printer["temperature_sensor pico_temp"].temperature %}

Then we can use that as follows:

M117 "Pico: {core_temp}"

or:

{% if core_temp > 60 %}
    M117 Too hot!!!
{% endif %}

Klipper Docs

Neopixel LED

Configure Neopixel LED

Many Pico boards (such as the QTPY varients) have a built-in RGB LED. Then pin used for this may vary between models, but the configuration format is the same.

[neopixel pico_led]
pin: my_pico: gpio12
initial_RED: 1.0
initial_GREEN: 1.0
initial_BLUE: 1.0

Note how the pin is assigned.

my_pico: tells Klipper the pin is on our Pico mcu.

gpio12 is the pin used on the SeeedStudio and Adafruit QTPY RP2040 boards.

The initial_RED/GREEN/BLUE settings define the color/brightness that should be used at startup. Each color channel can be assigned a value between 0 and 1.

Control Neopixel LED

Neopixels are controlled using the SET_LED command:

SET_LED LED=pico_led RED=1 GREEN=0 BLUE=1

This example will turn the LED purple.

To turn it off:

SET_LED LED=pico_led RED=0 GREEN=0 BLUE=0

Klipper Docs

Configure Neopixel Enable Pin

The QTPY boards (and perhaps other RP2040 boards with LEDs) require you to also pull the neopixel_enable pin high.

This is done as follows:

[static_digital_output enable_pico_led]
pins: my_pico: gpio11

This will tell Klipper to pull that pin high when the mcu connects. gpio11 is the pin used for this neopixel_enable function on the SeeedStudio and Adafruit QTPY RP2040 boards.

Static LED

Configure Static LED

The SeeedStudio QTPY RP2040 also has a basic LED indicator which is not RGB but the brightness can be controlled via a gpio pin.

I don't believe this feature is available on the Adafruit variant.

To use this from Klipper, include the following in your printer.cfg file:

[output_pin _my_pico_status]
pin: my_pico: gpio25
value: 1
shutdown_value: 0

Note that in this case I'm choosing to name the component with an underscore at the start: _my_pico_status to prevent it from showing up in the UI.

value: defines the startup value for the LED. Much like the color channels of a neopixel, this accepts any value between 0 and 1.

shutdown_value defines the value sent in the case of a shutdown caused by error or emergency-stop. It is not used during normal shutdown performed by disconnecting Klipper. The same 0 to 1 range applies.

Control Static LED

The ouput_pin is controlled with the SET_PIN command:

SET_PIN PIN=_my_pico_status VALUE=0.5

This example would set the brightness to 50%.

To turn it off:

SET_PIN PIN=_my_pico_status VALUE=0

Klipper Docs

Organizing your config

Once we start adding all these components and macros, the printer.cfg file can get pretty crowded.

We can use the [include] feature to better organize our config.

For example, let's put all the configurations we just did into a new pico.cfg file.

The pico.cfg file:

[mcu my_pico]
serial: /dev/serial/by-id/usb-Klipper_rp2040_E660C062135C6A24-if00

[temperature_sensor pico_temp]
sensor_type: temperature_mcu
sensor_mcu: my_pico
min_temp: 0
max_temp: 100

[neopixel pico_led]
pin: my_pico: gpio12
initial_RED: 1.0
initial_GREEN: 1.0
initial_BLUE: 1.0

[static_digital_output enable_pico_led]
pins: my_pico: gpio11

[output_pin _my_pico_status]
pin: my_pico: gpio25
value: 1
shutdown_value: 0

[gcode_macro GET_PICO_TEMP]
gcode:
    {%set core_temp = printer["temperature_sensor pico_temp"].temperature %}
    M117 "Pico: {core_temp}"
    {% if core_temp > 60 %}
        M117 Too hot!!!
    {% endif %}

We can save that file in the same directory as the printer.cfg file and then include it with the following line in the printer.cfg file:

[include pico.cfg]

For more information:

This Section of my Advanced Guide

Config Reference

Useful Links

Config Reference

Pico + ADXL Accelerometer Build Guide