- no decade caps, but always largest capacitance for case size
- at least one bypass cap per pin
- ground always points down, supply always up
- application notes often suggest untested (emc), old practices that do no longer work in modern designs
- place series termination resistors on fast signals and all signals that leave the board
- consider bjts for signals before mosfets
- comparators usually are open drain and need pull ups
- indicator LEDs that shouldn’t be super bright can use 10k resistors
- i2c pull ups can be 10k for low speed and 3.3k for fast speed
- spi needs pull ups on cs and clk, mosi good idea. 10k or 100k.
- 10k pullup on reset
- use pull resistors to permanently tie enable signals to a rail
- use standard debug connector pin out (swd, esp-prog)
- do not use 1117 ldo, there are better ones
- ceramic capacitors lose capacitance at applied voltage
- do not use ldos for more than 300mA for 5v->3.3v and more than 50mA for 12v input
- 12v in a car can go above 14v, and above 60V in stress conditions
- use 5.1k resistors on usb type-c peripheral cc lines
- do not use ferrites
- you most likely do not need a separate analog voltage rail
- do not use separate analog ground
- try to use differential signaling when running long cables (e.g. CAN, RS-485, Ethernet) to reduce emissions
- input pins need to have defined voltage; place pull resistors if the pins don’t have internal pulls
- prefer leaded parts over leadless (QFN, DFN, BGA) parts
- consider adding test poins for all signals and power rails, but especially for those signals that do not have exposed pads. add several ground test points.
- ESD protection on every line that leaves the enclosure or that can be reached by the user (e.g. tactile button)