FTDI v ISP/ICSP v UART/USART v SPI

These terms cause a bunch of confusion.

Programming

You probably program these things with avrdude. See man avrdude.

Bootloaders

It is popular to put a bootloader on your chip. This takes up some space but allows the chip to "reprogram" itself by writing to its own flash.

Some systems have a separate ISP/ICSP or UART chip on board and you can use that to reprogram the chip without a bootloader.

The purpose of both of these systems is that you can reprogram the chip while it is on-board.

Disambiguation

FTDI is one implementation of UART.

ISP/ICSP is a set of similar protocols created by different companies, AVR ISP is used with AVR chips and is common/popular.

UART is common. USART is uncommon. Many devices support UART and not USART. USART is similar to SPI.

Definitions

asynchronous - uses no clock
synchronous - uses a clock

Synchronous

USART
SPI
ISP/ICSP

Asynchronous

UART (therefore FTDI)

References

Thread on USART v SPI
Wikipedia
- SPI
- ISP/ICSP
- UART

SPI - Serial Peripheral Interface

Direction: Simplex

Channels: 1

I used SPI via Raspberry Pi (original) GPIO pins to program a flash chip that I soldered onto my lenovo x220 mainboard to install coreboot.

ISP/ICSP - `In-system Programming` or `In Circuit Serial Programming`.

Direction:

Channels:

This allows you to program on-chip. There are multiple incompatible ISP technologies.

AVR ISP is very popular right now.

Wikipedia states: "A ISP USB cable must typically be shorter than 180cm"

UART - `Universal Asynchronous Receiver/Transmitter`

Direction: Simplex, Half Duplex, Full Duplex

Channels: 1+ (typically 1 channel)

The foundation of UART is the shift register and clock.

Raspberry Pi <-> Arduino via UART

Note that in the demo, a voltage divider is used to talk from the arduino to the raspberry pi. The raspberry pi uses 3v3 on the UART tx/rx pins. The arduino pin 11 (MOSI) gets the voltage divider to the Raspberry Pi GPIO 16 RxD UART.

Demo

What about Raspberry Pi -> ESP8266EX?

Maybe the Raspberry Pi would be a good way to program the ESP8266EX?

FTDI is UART

Direction:

A common chip in 2017 is FT232RL which goes USB to UART.

The ESP8266EX AiLight uses the [BoyaMicro 25Q32ASSIG Chip] as an ISP.

Future Technology Devices International is a company that apparently makes people sad sometimes.

To use FTDI you need a 512 byte bootloader.

A number of FTDI programmers exist but do not always seem branded as such.

Arduino: FTDI or ISP?

Arduinos used to have an FTDI chip but it was too expensive so they moved to a second chip that can do USB ISP on the primary chip.

UART (FTDI) Programmers

Sparkfun FT232RL Breakout: 3v3 5v
- These are called 'USB to serial IC' boards
- These use miniUSB, there is a different offering for microUSB
- Offers DTR pin but not RTS; DTR resets your arduino; other models offer RTS
Adafruit FTDI Friend FT232RL Breakout: 3v3 and 5v
- Offers RTS pin and DTR as a pad DTR guide
- Offers 3v3 and 5v - signal is 3v3 (5v compatible), power is 5v... make sure you know what you are doing

Other brands

The ESP8266 AiThinker Light Bulb needs an UART programmer
- recommended by the developer: AiLight Jig
- He got some boards from china, I have asked him for a link to the seller

Hardware

JTAG Programmers - Apparently the industry standard. Can we make these for fun?
AVR ISP Programmers
Standard issue microcomputers
- Raspberry Pi
- Arduino Uno
- BusPirate

The CP210x USB to UART from Silicon Labs exists

It is cheaper than the FTDI FT232RL.

Adafruit offers a low-cost breakout board of this chip and it is also in other popular USB->UART devices.

Raspberry Pi

How does this fit into the picture? I have used it with flashrom as a flash programmer for a lenovo x220 with a test clip, how is this related to everything else?

BusPirate

Apparently the BUS Pirate can do all of this, but requires configuration.

Arduino Uno

Careful! Transmits at 5V which will fry the Raspberry Pi and esp8266.

Software

flashrom
avrdude
Arduino IDE