I'm trying to make my own nucleo board using STM32F303ZET6. I have downloaded and inspected the schematic documents that stm shared. I will use this board as rocket flight computer so I want the board to be able to:

  • Read sensor data using I2C. (BMP180,BMP280,LSM6DS33,BNO055)
  • Use SPI port for the RF module and SD card.
  • Use UART port to read GPS data from NEO-M8N.

All the screenshots that I have posted here are from the STM32F303ZE schematic. You can click here. For the programming part of this board I want to use the STLink V2 part from the original NUCLEO-F303ZE. So I will just rip the part off the pcb and use it externally. And then I will have jumpers from the programmer board to my board to be able to program my board.

Question #1: Can I replicate only the connections below with jumper cables (also 3V3 and GND) to program the board I want to make. enter image description here

* Question #2: Can I just connect all the VDD and VDDA to 3V3, connect all the VSS and the VSSA to GND?enter image description here Question #3: On the schematic there are 2 oscillators for the MCU. 8MHz and 32.768KHz (Is the 32.768KHz oscillator 32MHz or 32KHz? I don't understand the notation.) I want to use the MCU at 72MHz clock speed but I don't understand how that can be reached with these external oscillators. Can I reach this value with the internal clock? If I want to use te internal clock should I remove the oscillators? enter image description here

Question #4: I have seen opamps on the schematic do I need it for the functions that I have listed above?


3 Answers 3


In addition to the answers already given, I would like to point one one more issue that wasn't mentioned.

The 8 MHz HSE clock circuit is connected to the ST-Link and then routed via the MCO line to the STM32F303. If you remove the ST-Link, you also lose the HSE clock.

Without the HSE clock, you can still achieve a system clock of 72 MHz. But there are other restrictions, e.g. you cannot use USB without HSE.

Therefore, it might make sense to add an 8 MHz crystal and the required capacitors to your design.

  1. Yup. Maybe consider JST-GH connectors for easy access. Otherwise 2.54mm breadboard pitch connectors are fine. Test pads are enough too if you want to go with soldering or pogo pins.

  2. Yes. There may be instances where the specifications require separated rails but it should be fine for your application.

  3. The 32.768 kHz is for RTC timekeeping. It divides evenly to one per second. You won't need this unless you want accurate timestamping without dividing the master clock. You will be able to clock to 72 MHz by using the chip's internal PLLs. PLL takes stable reference frequency and can multiply it to a higher frequency, effectively.

  4. I don't think you need opamps for a rocket flight controller. Showing the schematic might help us better understand the context

More info on clocking:

I've used other chips within the STM32 family. You will be able to select clock source using the on-chip clocking logic. You should be able to select between low speed internal (LSI), high speed internal (HSI), as well as low speed external (LSE), and high speed external (HSE). External means that it's not on the STM32 chip and must be included on the PCB. Generally external oscillators/crystals are quartz, which have much better accuracy and precision (generally under 100 ppm if I recall correctly) compared to the internal RC oscillator (± few percents).

You should be able to get away with PLLing the internal oscillators to the desired 72 MHz but it might not be ideal.


A1) Yes but beware connecting power supplies together so that if both boards are self powered then it may not be a good idea to connect 3V3 supplies together.

A2) Yes

A3) The MCU has internal clocks. The MCU has a PLL to multiply the frequencies to 72MHz. You can leave out crystals if you don't want to use them. But if you are doing anything that requires a precise clock then you need an external clock source. As you mention you want UART communication that is usually a good enough reason for you to use the 8 MHz crystal. You don't need the 32kHz crystal unless you want to use battery backed real time clock.

A4) Nothing above needs an op amp unless you know something that does.


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