STM32F0 Application

We are reusing this chip because it is a part of https://github.com/UWARG/ZeroPilot-HW/blob/master/sch.pdf as the safety chip of the flight controller. The datasheet for the chip can be found at https://www.st.com/resource/en/datasheet/stm32f030f4.pdf .

The purpose the chip is to connect to the H7 chip, handle basic sensor connections, and output to PWM and PPM for the grabber and main rotors.

The general pinouts, PA through PD, are easily copyable from ZeroPilot and most of which are.

Because we are not using the internal ADC we are not satisfying the requirement to power on VDDA before the VDD pins. For the NRST circuit, the chip has an internal pull up resistor so it is connected with a 0.1uF capacitor and switch very similar to the H7. The boot pin can be held low or high to select different boot modes as specified in the data sheet. To accommodate this I have included two DNP resistors, one pulling up, and the other pulling down.

The clock circuits are also extremely similar as is found in ZeroPilot. LSE as specified in the datasheet must be 32.786 Hz and both capacitors must be identical ranging from 5pF to 20pF according to the datasheet. I used 10pF capacitors for simplicity. The HSE is 8Mhz nominally though can range from 4-32Mhz. For choosing the capacitors I used the following formula CL=((C1*C2)/(C1+C2))+Cstray which was also used for the H7’s clocks. I asserted that C1=C2 to ensure that the two capacitors was the same and estimated Cstray=5pF. I used 10pF=CL and computed for the value of the capacitors which was 10pF.

To start with decoupling capacitors we see on page 42 of the datasheet:

The datasheet specifies in the image above that paragraph that we need two 100nF capacitors, one 4.7uF capacitor, one 10nF capacitor, and one 1uF capacitor. This requirement is echoed in the pervious Zeropilot design with a total of five bypass capacitors.