小小的一把尺子，几乎是每个工程师桌上必备，因此很多厂商打起了这方面的主意，比如Adafruit做的这把尺子：
还有这个用于体验CircuitPython的称之为PyRuler的尺子，直接把电路做在了尺子上：
它的功能：
ATSAMD21E18 32-bit Cortex M0+ - 256KB Flash, 32 KB RAM, 48 MHz 32 bit processor
Native USB supported by every OS - can be used in Arduino or CircuitPython as USB serial console, Keyboard/Mouse HID, even a little disk drive for storing Python scripts.
Can be used with the Arduino IDE or CircuitPython
Four capacitive touch pads.
Lots of LEDS - Built in green ON LED, red pin #13 LED, RGB DotStar LED, plus red/yellow/green/blue matching LEDs for each capacitive touch pad
5 GPIO header pins are available and are not shared with USB or the touch pads/LEDs - so you can use them for whatever you like! Digital I/O with pullup/down. 3 ADCs, 1 DAC, 2 PWM, 3 extra captouch sensors
Can drive NeoPixels or DotStars on any pins, with enough memory to drive 8000+ pixels. DMA-NeoPixel support on one pin so you can drive pixels without having to spend any processor time on it.
Native hardware SPI, I2C and Serial available on two pads so you can connect to any I2C or Serial device with true hardware support (no annoying bit-banging). You can have either one SPI device or both I2C and Serial.
Reset switch for starting your project code over
Power with either USB or external output (such as a battery) - it'll automatically switch over
今天我们再来看一把专门给树莓派爱好者设计的尺子，这是在Kickstarter上众筹的一款尺子。：
那么它都有些啥呢：
正面：
15CM, and 6 inch rules with 1mm and 1/16" graduations.
Raspberry Pi 4 GPIO pinout with through plated holes.
Wire sizes from 10AWG to 28AWG.
Circuit board trace widths from 10mils to 80mils, and .25MM to 2MM.
Ohm's Law.
背面：
Resistor color code.
LED package and pinout.
Bipolar junction transistor packages and pinouts
Field effect transistor packages and pinouts .
Font height in mils and mm.
Formula for resonate frequency.
Formulas for capacitive and inductive reactance.
USB 2.0 plug pinouts.
RJ-45 T-568B pin out.
是不是很有用呢？
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