Device installation guide

Start with the physical installation of the PowerSensor, then install the firmware to the device. When both are completed succesfully, install the host library with this guide and get to know the device with the user guide.

Installing the PowerSensor

Before starting, turn off and unplug the power of the host system. In the case of a GPU, a PCI-e riser card or cable is needed to be able to measure the 3.3 V and 12 V power coming from the PCI-e slot of the motherboard. 12 V power coming directly from the PSU can be connected to a PowerSensor3 sensor board. A second ATX power cable should be used to connect the PowerSensor3 sensor board to the GPU. Take care to use sensor boards with appropiate voltage and current sensors, taking into account the maximum voltage and current:

Connection	Voltage (V)	Maximum power (W)	Maximum current (A)
PCI-e 3.3 V	3.3	10	3.0
PCI-e 12 V	12	65	5.4
ATX 6-pin	12	75	6.3
ATX 8-pin	12	150	12.5

After connecting all relevant power cable, connect the microcontroller to a USB port on the host. After making sure that everything is connected correctly, turn on the host system.

Building the firmware

We provide pre-built binaries here for default configurations using either any of the supported microcontrollers. For non-default settings or other customizations, the firmware can be built with the Arduino toolkit as outlined in this section. Note that the pre-built binaries use a modified USB transmit buffer size, see the USB Buffer size section.

The firmware is dependent on a few Arduino tools, these should be installed before continueing. First the arduino-cli package can be installed on Linux via:

curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh

Next, the stm32duino package should be installed, this ensures that STM32 boards can be used in combination with arduino. Start by updating the arduino core:

arduino-cli core update-index

Then, if there is not already a config file at ~/.arduino15/arduino-cli.yaml, create a config file with:

arduino-cli config init

Open the configuration file in any editor and add new board manager URL to:

board_manager:
  additional_urls:
    [https://github.com/stm32duino/BoardManagerFiles/raw/master/STM32/package_stm_index.json]

Update the core again:

arduino-cli core update-index

arduino-cli will automatically install the STM32 core when building the firmware.
NOTE, the current latest version (2.5.0) does not work with PowerSensor3. See this Github issue for details and a workaround.

Then run the following command in the device folder to build the firmware with default flags:

make device

For an STM32F401 or STM32F411 Black Pill, the fimware will be written to PowerSensor/build/STMicroelectronics.stm32.GenF4/PowerSensor.ino.bin, for the STM32F407 Discovery, the file location is PowerSensor/build/STMicroelectronics.stm32.Disco/PowerSensor.ino.bin.

Uploading the firmware

First make sure the device is booted in DFU mode. This is typically achieved by holding down the BOOT0 button and pressing the RESET button. Confirm that the device has entered DFU mode with either:

lsusb
dfu-util -l

The firmware can be uploaded with dfu-util or arduino-cli. The latter can only be used when compiling the firmware yourself. To upload with dfu-util run the following command, adapting the -a and -i options as necessary to match the output of dfu-util -l:

dfu-util -a 0 -i 0 -s 0x08000000:leave -D /path/to/PowerSensor3/firmware.bin

To upload with arduino-cli, first make sure you can build the firmware as outlined in the previous section. Then run the following command in the device folder, adding any flags in the same way as with the make device command.

make upload

If the firmware is uploaded successfully, the device will be reset and start running the PowerSensor3 firmware.

Build customization

There are several options available to customize the firmware build. These options can be append to the make device and make upload commands.

Target microcontroller

A flag is provided to set whether the firmware is built for an STM32F401, STM32F411 (default) or STM32F407 microcontroller.
Option name: DEV
Allowed values: F401, F411, F407
Example:

make upload DEV="F401"

Extra flags

Defines that would usually be given to the compiler with the -D option can be set with make using the FLAGS option. Currently supported flags relate to the display: -DNODISPLAY disables the display completely. This also means that the external libraries, located in PowerSensor/Libraries are not used. -DTFT_BLUE changes the display type from the default green tab to a blue tab. Effectively, this only inverts the display colours. -DDEMO enables updating the display during measurements, meant for demos. Updating the display interferes with the measurement interval, so this mode should not be used when accurate measurements are required. Multiple flags should be separated by a space. Example command:

make upload FLAGS="-DTFT_BLUE"

USB buffer size

The STM32 USB library has a default transmit buffer size that is too small to handle the high data rate used in PowerSensor3. When using the default buffer size, you will most likely see dropped data. The buffer size is set in the cdc_queue.h file, part of stm32duino. This file is usually located at <Arduino folder>/packages/STMicroelectronics/hardware/stm32/2.3.0/cores/arduino/stm32/usb/cdc/cdc_queue.h

We provide a patch file to increase the buffer size (tested with version 2.3.0 of stm32duino), as well as a Python script to locate the stm32duino folder. To automatically update the cdc_queue.h file, run something like this from the root of the PowerSensor3 repository:

REPO_ROOT=$PWD
STM32_DIR=$(python/get_arduino_stm32_directory.py)
cd ${STM32_DIR}/cores/arduino/stm32/usb/cdc
patch < ${REPO_ROOT}/patch/cdc_queue.patch

Then proceed with building the firmware with arduino-cli as usual.

Next steps

After installing the device, proceed with installing the host library with this guide.