STM32CubeMX

Download it here and wait for it to install.

After installing it and opening it, you should be presented with this screen:

Click on ACCESS TO MCU SELECTOR as we are going to create a new project based on the MCU that we are using: in this case, STM32F722RET.

After searching for the MCU, you should see this screen:

Here, it shows different variations of that version for the STM32, but we are going to select the STM32F722RET6 version as it is the one that has the most in stock on LCSC.

After that, hit "Start Project" at the top. If any windows pop up, say yes.

After loading/downloading the firmware, you should be greeted with this window:

For now, enable the first ConceptI2C channel. This will be for the battery charger and pressure sensor. It should look like this:

Also, be sure to select pins on either side for the battery charger interrupt and chip enable pins. The BQ_INT pin should be set as a GPIO_EXTIx (x is any number) pin as this lets the STM32 know that this pin is going to be an interrupt pin.

For BQ_CE, make sure that there's a pin set to GPIO_Output. According to the datasheet, when the pin is low, charging is on, and when it's high, the battery doesn't charge. We can change this later in the code for further customization in case you don't want the battery charge controller running during flight.

Then enable an SPI channel for the IMU. You are free to use whichever channel you wish, but I am going to select the first one. Select Full Duplex Master as the STM32 will be the master and the IMU the slave, and full duplex because we are using both MOSI and MISO and not just one channel for input/output (half duplex/SDIO).

There is also an option under the selection to activate a Hardware NSS Signal. This is used if we have just one device under the SPI bus and makes it so that the STM32 manages the Chip Select pin instead of us having to select a GPIO for it. I enabled it as Hardware NSS Signal Output as the IMU will be the input. After selecting SPI, it should look like this (it can be different if you want to use a different pin for the Chip Select):

Also, don't forget to add the 2 interrupt pins on the IMU as GPIO_EXTIx (x is any number):

After you've done that, it's time to select USB_OTG_FS. This means USB On-The-Go Full Speed, and it differs from USB_OTG_HS (USB On-The-Go High Speed) as it is slower and doesn't need any extra pins to configure. It's sufficient for our needs of flashing and sending serial data.

Set it to host or device (you'll be changing this later depending on your needs). For now, I will leave it as host, and it shows where the USB pins are on the chip.

Now enable SDMMC as this is the communication protocol that we will be using to write/read to our microSD. This should be enabled and set to a 4-bit bus.

Also, remember to add an extra pin next to it for the card detect pin and make it a GPIO_Input:

Go to the System Core tab, then click on RCC, and set both the high-speed clock and low-speed clock as a crystal/ceramic resonator.

By doing this, we are telling the STM32 that we will have some external clocks that it can use to achieve faster/stable clock timing throughout the entire chip. We will edit this in KiCad later along with the pins.

Now go to the Timers section. Here is where we can edit the PWM pins for the servos. Select any timer that has channels that support PWM and select 2 PWM Generation CH channels. We will be able to edit the duty cycle later in the firmware.

Also edit the Clock Source and set it to the internal clock. This is needed for the PWM generation as it needs a clock to time the signals correctly.