Ideas

some ideas about the functions:

• either for signal processing or for control
• either in continuous time (analog) or discrete (digital) and from one another and vice-versa
• linear or non-linear

Signal processing

Notes

converters vs filters:

• converters seek to maximize energy transfer between input signal and output signal
• filters seek to remove energy from signal. The energy to be removed is decided at by the designer as unwanted under reasons specific to each design (anti-aliasing, noise reduction, x-talk removal, blockers, ...)

Convertors

* A2D:
    * voltage to digital (most often simply refered to as `ADC`)
    * current to digital
    * time to digital (TDC)
* D2A
    * DAC
* A2A
   * voltage to voltage: buck, boost, sepic, AC/DC, ...
   * current to voltage: TransImpedance, ...

overview in below table

input\output	voltage	current	delta time	frequency	digital	R	C	L
voltage	DCDC, DCAC, ACDC	transconductance, V2I	VTC	V2F	ADC
current	TIA	current mirror	?	?	i-ADC
delta time	integrator	?	pulse shrink/spread, delay	?	TDC, timer
frequency	F2V	?	?	PLL, DLL, ...	FDC
digital	DAC	i-DAC	PWM?	PWM	DSP	dpot
R
C								gyrator
L

filters

* linear: LP / HP / BP ...
* non linear:
    * deadband
    * hysteresis
    * rate limiter
    * saturation
    * ...

maths

* abs value
* sign
* sqrt
* summation
* exponential
* gain block
* log10
* min / max 
* product
* greater than / lesser than
* derivative
* integral

Control Processing

logic

* and / or / xor / ...   

    * [fuzzy logic Zadeh operator](https://en.m.wikipedia.org/wiki/Fuzzy_logic#Fuzzy_logic_operators) `AND(X,Y)` == MIN, `OR`== MAX; `NOT(X)` == 1-X

* if then else

events

* edge triggered
* flip flop: SR/JK
* zero cross detect / - to + / + to - or ZCD
* time delay

signal routing

* look-up tables (many to many)
* DEMUX (1 to many)
* MUX (many to 1)
* switch (1 to 1)

Conversion to electricity

Energy	Effect	Device
Thermic	Seebeck effect	type-K
Thermic	Seebeck effect	TEG
Thermic	Peltier effect
Thermic	Thomson effect
Light	Photovoltaic	c-Si
Light	Photovoltaic	a-Si
Light	Photovoltaic	OPV
Light	Photovoltaic	DSSC
Light	Photoelectric	LED
Light	Photoelectric	laser
Light	Photoelectric	photodiode
Light	Photoelectric	gas discharge
Chemical	Battery	Li-ion
Chemical	Battery	NiMH
Chemical	Battery	NiCd
Chemical	Battery	NiCd
Chemical	Battery	Fuel cell
Chemical	Photo-electrode	pH
Chemical	Photo-electrode	oRP
Chemical	electro-chemical	3 lead cell
Chemical	electro-chemical	2 lead cell
Thermal	Pyro-electric
	Tribo-electric
Cinetic	piezo-electric	microphone
Cinetic	piezo-electric	buzzer
Cinetic	?	dynamo
Magnetic	?	hall
Electro-Magnetic	?	antenna

Resistance dependant

• Light
• Strain

Capacitance dependant

*MOXFET

Schematics guidelines

Readability

• Power supplies use supply symbols (not wires) with useful names
• Positive supplies point up, ground and negative supplies point down. Always.
• All important nets are descriptively named
• Net “stubs” (nets visually connected to only one pin) use an “off-sheet” type of label with the correct In/Out/Bidirectional flag shape and cross reference info (sheet / location)
• Functional blocks are clearly labeled (plenty of whitespace around it, or maybe even a box)
• Functional blocks have text that describes what they do and their requirements (e.g., Vbatt to 3.3 V @ 1 A switching power supply”)
• There's a frame around the schematic
• It's clear where your power is coming from and what the power requirements are (V/I)
• Data flow (inputs, outputs, requirements) are clear and labeled
• All connectors have text that describes what they go to
• Route wires at a consistent distance from each other and avoid crossing net wires as possible
• Groups of nets above about ≥ 4 nets collected into buses

Schematic Symbols

• All symbols are schematic symbols, not packages (inputs on left, outputs on right, power on top and bottom)
• Pins have correct electrical rule check (ERC) direction (inputs, outputs, passives, etc)
• Components with symbolic shapes use those shapes (e.g, opamps are triangles)

Part values

• Capacitors have the appropriate voltage (usually ≥ 2x working voltage, also see this) and specify dielectric type if necessary
• Special case capacitors marked with power and tolerance
• Power dissipation checked on all resistors
• Special case resistors marked with power and tolerance
• Layout features that are circuit elements (e.g., copper inductor) are labeled in the schematic

IC Key Points

• MOSFETs oriented correctly WRT the body diode (!), with note if intentionally forward conducting
• Check IC part numbers reflect the correct package type
• Small, low ESR (e.g., ceramic) bypass capacitors on all IC supplies (check datasheet for values)
• Check voltage inputs and outputs match across power domains (e.g., 5V to 3.3V)
• Check that powered-off domains are not phantom powered by their inputs from other circuits (including test circuits, like UARTs)
• Check for UART TX/RX swaps (TX to RX, RX to TX)
• Check for pull-up/down resistors on open collector/drain outputs (e.g., I2C lines)
• Check for required pull-up/down resistors to set nets in a default state at power up
• Check for no floating nodes (especially during sleep states)

Design for Test

• Place test points on critical signals, especially power and ground
• Make sure crocodile or scope can easily use those when probing nearby nodes
• Consider the right side for SMT test points, or use through-hole test points (esp for bed-of-nails testers)
• Add debugging hardware (e.g., LEDs, UART connectors, jumpers, scope probe points, etc)

Design for Fail

• Group components in separable modularly powered blocks and use zero ohm resistors or cuttable jumpers to disconnect (especially for switching power supplies!)
• Unused pins (especially GPIO) should go to usable test points. Consider adding some random pull-up and pull-down resistors connected to a test point on the board, too
• Consider somehow encoding your PCB hardware revision in hardware (GPIO pullups, etc)
• UART (serial port) TX/RX are always mixed up, consider cuttable jumpers here
• Consider over-voltage/ polarity input protection if you or your user can screw this up

Electrical Rule checks (ERC)

• No unapproved errors OR warnings in the ERC
• All important excluded errors/warnings have a comment on why they’re approved

BOM Fixes

• Add “MFR” (Manufacturer) and “MPN” (Manufacturer’s Part Number) to all components as attributes
• Add a datasheet link and description to part attributes

MISC

• Peer reviewed by at least one person not involved in the design.
• Check stock at 1+ distributor
• Re-run ERC and double check your approved errors, looking for accidentally approved errors
• Revision Control:
  • record changes to the schematic in a table or in nearby documentation
  • Update your schematic version and/or date