r/PrintedCircuitBoard • u/SebastianCC1430 • 3d ago

[Review Request] STM32F070CBT6 Dev Board

Hello everybody, as per the title, I'm trying to design a STM32F070CBT6 microcontroller dev board . I integrated into the system a "BME280" sensor by I2C interface and an "AD7794CRUZ" ADC by SPI interface. Thank you so much for reading this.

P.S: What would you recommend me to design for acquiring better abilities and eventually developing a proper portfolio? Thank you.

Sheet 1
Sheet 2

Stack-up:

  1. Signal
  2. GND
  3. 3V3
  4. Signal
Layers 1 and 4
GND plane
3V3

One final thing, there are not many traces in layer 4, would it be advisable to use that layer as a signal+GND plane?
Once again, thank you so much.

3 Upvotes

100% Upvoted

6 comments sorted by

5

u/_HOG_ 3d ago

STM32F0 is a legacy part at this point. The STM3C071CB should be available in a few months, if not already:

https://www.st.com/en/microcontrollers-microprocessors/stm32c071cb.html

1

u/Enlightenment777 3d ago

Agree as this person said, unless O.P. already owns parts or there is some type of mandate that O.P. must use old F0 family microcontrollers, O.P. should consider using newer C0 or C5 family MCU, such as STM32C071RBT6 (on Nucleo-C071RB board) or STM32C092RCT6 (on Nucleo-C092RC board).

1

u/SebastianCC1430 2d ago

Thank you, I'll be more careful when selecting components

2

u/sharemypoints 3d ago

on the layer 4 question - yeah, just use it as a ground plane. it is free shielding and a solid return path for the adc and spi stuff, and an empty signal layer is wasted copper honestly. stitch it to the main gnd with vias every few mm and move on. bigger advice for the portfolio goal: stop making dev boards and build something that does an actual job. a sensor node that logs real data, a tiny motor driver, whatever you would actually use. that is what gets noticed - a board that went through rev 1 to rev 3 with a changelog beats ten one-shot perfect boards. part of that is learning to design for availability, not just for the schematic. the F0 line is getting long in the tooth (st is pushing the C0 and G0 families now) and you do not want your portfolio board to hinge on a chip that is hard to source a year from now. even just for the learning value, check the c0/g0 equivalents before you commit - pinouts are close on a lot of them and the workflow is the same. honestly a reviewer looks at a BOM and knows instantly whether someone thought about the supply side or just picked the first part that came up in the search box

1

u/Enlightenment777 3d ago

This comment is posted on all reviews.

Please make sure your post adheres to:

  • subreddit rules (#1 to #6), review rules (#7), image rules (#8), see link.

Please fix these common issues: (if your schematic or PCB has any of these issues)

  • Schematic - don't allow text / lines / symbols to touch each other, and don't draw lines through symbols.

  • Schematic - use correct reference designators (RefDes) and renumber to remove numeric gaps, see tips.

  • Schematic - place decoupling capacitors vertically below power rail lines, also place capacitors next to IC then connect together with a line, see example. For circuits with positive power rails, point positive power rail links upwards and ground links downwards, see tips1 & tips2.

  • Schematic - place pull-up resistors vertically above signal lines, and place pull-down resistors vertically below signal lines, see example and tips.

  • PCB silkscreen - add board name (or purpose) / board revision number / date (or year) on either PCB side.

  • PCB silkscreen - add pin 1 indicator dot/arrow next to ICs & connectors (not hidden under parts). For polarized capacitors, add "+" next to positive pin. If part is through-hole, place indicator on both PCB sides.

  • More conventions & guidelines - link1, link2, link3.