What are an FTDI adapter and a breakout board, and why are they in the IoT prototyping toolkit?

An FTDI adapter is a USB-to-serial converter that lets a laptop program or talk to a board without its own USB port; a breakout board mounts a tiny chip on a PCB with standard pins so it can be wired up by hand.

Prototyping is mostly about getting parts connected before designing a real circuit board. The toolkit reflects that:

• FTDI adapter. Named after the chip maker FTDI, whose USB-UART chips are the classic choice. It exposes TX, RX, power and ground on a header. Boards like the ESP32 dev board build this in; smaller boards (an Arduino Pro Mini, a bare module) leave it off to save size and power, and you plug an FTDI adapter in only while programming.
• Breakout board. Modern sensors come in surface-mount packages a few millimetres wide. A breakout puts one on a small PCB with 2.54 mm header pins, plus the support parts it needs (regulator, pull-ups).
• Buttons, LEDs, resistors as the basic inputs, outputs and current limiters.
• Power adapter and breadboard to supply and connect everything without soldering, and a case for the finished prototype.
• Screens and instruments. Small OLED or TFT touch displays show data on the device itself; measurement instruments (a multimeter, an oscilloscope or logic analyser) let you see and record the signals when something doesn't work, and measure current draw for power efficiency.

Tip: if you can't see the signal, you are guessing. The instrument is what turns "it doesn't work" into "the I2C clock never toggles".

Go deeper:

• Wikipedia — FTDI — the company behind the USB-serial chips, and the 2014 driver controversy over counterfeit parts.