The Reference Shelf
The one-sheet reference cards that hang at the bench — protocols, chips, and power parts, each distilled from the datasheet onto a single printable page. Free to download.
These are the reference cards that hang at the bench. Each one takes a datasheet or a protocol spec and boils it down to the page I look at while soldering: what the part is, the few specs that matter, the pins in use, and the gotcha that bit someone once. They were written for one shop’s builds, so the “why it’s in our system” sections describe our circuits, not yours — but the specs and the gotchas travel.
Offered as-is. One page each, monospace, meant to be printed and taped to a wall. If a number matters to your build, verify it against the manufacturer’s datasheet before committing copper.
Protocols
| Sheet | What it covers | Notes | Download |
|---|---|---|---|
| DMX512 | Stage-lighting control | 250 kbaud over RS-485, 512 channels per universe, why isolation is mandatory on stage. | |
| Art-Net | DMX over the network | Many DMX universes packed into UDP over ordinary Ethernet; the 2.x.x.x convention. | |
| MIDI | Musical instrument control | The current-loop serial protocol and its opto-isolated input convention. | |
| RS-485 | Differential serial physical layer | The balanced two-wire electrical layer underneath DMX and long serial runs. | |
| I2C | Two-wire peripheral bus | Addresses, pull-ups, and the short-reach bus most small peripherals speak. | |
| SPI | Four-wire peripheral bus | The fast clocked bus for ADCs, DACs, and anything daisy-chainable. | |
| UART | Asynchronous serial | Plain start-bit/stop-bit serial — the layer everything else is built on. | |
| USB | Universal serial bus | What a device needs to enumerate and where the data actually flows. |
Chips
| Sheet | What it covers | Notes | Download |
|---|---|---|---|
| LM324 | Quad op-amp | The single-supply workhorse; includes the not-rail-to-rail gotcha that a design review caught. | |
| MCP6004 | Quad rail-to-rail op-amp | The low-voltage counterpart — swings to its rails, but only up to 6 V. | |
| MCP3208 | 8-channel 12-bit ADC | SPI analog input; how the reference sets the scale. | |
| MCP4728 | Quad 12-bit DAC | I2C analog output with per-channel reference options. | |
| MCP23017 | 16-channel GPIO expander | I2C port expander for when the microcontroller runs out of pins. | |
| PCA9745B | 16-channel constant-current LED sink | SPI-set constant current per channel; dissipation math that decides the rail voltage. | |
| Vactrol cell | LED + photoresistor optical pair | Not a chip — a sealed LED/LDR pair used as an isolated variable resistance, nonlinearity and all. | |
| ESP32-C3-MINI | Small Wi-Fi/BLE module | The cheap single-core RISC-V module for simple networked boards. | |
| ESP32-S3-WROOM | High-GPIO Wi-Fi/BLE module | The bigger sibling — dual-core, ~36 GPIO, native USB; strapping-pin list included. | |
| 74LVC1G14 | Single Schmitt-trigger inverter | The one-gate signal cleaner-upper for slow or noisy edges. |
Power and interface
| Sheet | What it covers | Notes | Download |
|---|---|---|---|
| AMS1117 | Linear regulator | The ubiquitous LDO; dropout and dissipation limits. | |
| MP1584 | Buck converter | Step-down switcher for getting from a 12 V rail to logic voltages without cooking a linear part. | |
| AO3401A | P-channel MOSFET | The small high-side switch; gate thresholds and polarity notes. | |
| ADM2587E | Isolated RS-485 transceiver | Transceiver with its own isolated supply — the part that keeps ground loops out of a DMX input. | |
| THVD1450 | RS-485 transceiver | The non-isolated transceiver for runs that share a ground. | |
| H11L1 | Optocoupler with logic output | The standard MIDI-input opto; Schmitt output, no analog ambiguity. | |
| ULN2803A | 8-channel Darlington driver | Relay and load driver array with built-in flyback diodes. | |
| SIP-1A05 | Reed relay | A mechanical contact in a glass tube — a true open and a true short, no semiconductor in the path. |