I've put the same photo on my website, with various annotations about what the abreviations http://www.gammon.com.au/uno
giving a reading between 0 (for 0V) and 1024 (for 5V) using the analogRead function
between 0 and 1023
I'm not sure where to post this, but here goes ...Below is a modified photo of the Uno Rev3 board, with annotations about the extra meanings of some pins (not printed on the board):I personally find that when trying to hook up I2C or SPI, I can never remember which pin is SDA and which is SCL. Hopefully this photo will help others to quickly connect up their systems.Earlier boards are similar except that they don't have the ICSP header for programming the USB interface chip, and the extra SDA/SCL sockets for use with I2C.I find that the pins on the ICSP header (on the right) are useful for grabbing an extra +5/Gnd combination if I need to power other devices (or for hooking up a multimeter or logic analyzer).
QuoteI can never remember which pin is SDA and which is SCLSCL = Simply Connect Last (at least on an Arduino 328)SDA = Shouldbe Dhe Ather (The other)
I can never remember which pin is SDA and which is SCL