Practical Serial Communication

• Serial Port
  • RS-232
• many devices out there are serial
  • BASIC Stamp, Arduino, accelerometer, RFID
  • barcode readers in your favourite shop, magnetic stripe readers, you name it
  • very simple protocol, unlike USB
• but most computers today don't have a serial port any longer
• the 9-pin male connector (DB9=DE9) used to be ubiquitous at the back of PCs
  • serial connectors can have other shapes, Macs used to have it differently (RS-422) on DIN connectors
  • the Palm Pilot connector is also serial
  • many mobile phone connectors as well
• USB-serial converters
  • many are based on the FTDI chip, see their USB-serial drivers
    • though the name might not actually indicate that
    • converters made by Parallax for the Stamp use FTDI
    • so do Arduino USB boards
      • the Arduino software comes with a copy of the FTDI chip drivers, but in case of problems, install the ones from FTDI
  • not all converters work on the Mac (FTDI do)
  • upon USB connection, they create a serial port
    • the name of the COM port created on the PC cannot usually be assigned
      • you can find the COM port in the control panel of your operating system (Device Manager on Windows)
  • this is an issue especially if you have Bluetooth installed, that creates a large number of other COM ports
  • Arduino seems not to work with COM ports > COM9
  • one way to fix: uninstall using FTClean and reinstall
  • besides, on many computers there is software that continuously monitors COM ports
    • firewalls
    • mobile phone connectivity software
    • this might confuse devices like Arduino
  • still, unlike with Phidgets, making USB-serial work is the only installation difficulty
    • but you don't have to make it work on all computers, one per group is enough!
  • Power issues: may need a powered USB hub