Usb-Hardware.h File Reference

usb-bridge communicates over USB via FTDI USB Bridge IC FT221X More...

#include <stdint.h>
#include <avr/io.h>
#include "Usb.h"

Go to the source code of this file.

Variables
usb_reg	FtCtrl_ddr = &DDRC
usb_reg	FtCtrl_port = &PORTC
usb_reg	FtCtrl_pin = &PINC
usb_reg	FtData_pin = &PIND
usb_reg	FtData_ddr = &DDRD
usb_reg	FtData_port = &PORTD
usb_pin	FtMiso = PC2
usb_pin	FtChipSelect = PC0
usb_pin	FtClock = PC1
usb_pin	FtMiosio0 = PD0

Detailed Description

usb-bridge communicates over USB via FTDI USB Bridge IC FT221X

About the FT221X:

• Provides an embedded interface to a USB host
  • embedded system microcontroller is the FT1248 master
  • microcontroller sees FT221X as FT1248 slave
  • USB host sees FT221X as a USB device
  • USB protocol is entirely handled by the FT221X
• Data:
  • USB 2.0 Full Speed capable
  • Data transfer rate up to 1MByte/s (TODO: measure)
  • 512-byte receive buffer
  • 512-byte transmit buffer
• USB Driver options for Windows, Mac OS X, and Linux:
  • Virtual Com Port (VCP)
    • this is what pyserial uses
    • Chromation uses pyserial for the Python API
  • D2XX
    • FTDI-specific extended functionality
    • write your own Python package to wrap D2XX API calls
      • examples available on the internet
  • Both types free to download from FTDI:
    • https://www.ftdichip.com/Drivers/VCP.htm
    • scroll down to your operating system

FT221X usage in Chromation usb-bridge:

• USB to FT1248
  • usb-bridge uses FT1248 mode with 8-bit-wide data bus
  • USB protocol is entirely handled by the FT221X
    • usb-bridge firmware implements an FT1248 master
    • usb-bridge firmware is ignorant of USB specifics
• Program internal 2kB memory via FTDI GUI FT_Prog:
  • Chromation serial number: CHROMATION123456
    • each dev-kit has a unique six-digit serial number
  • Ft1248 Settings
    • Clock Polarity High: uncheck
    • Bit Order LSB: check
    • Flow Ctrl not selected: check
      • implements flow control when FT221X is not selected
  • CBUS Signals
    • C3: GPIO
• Flow control:
  • when FT221X pin CS# (Not Chip Select) is HIGH:
  • reflect status of receive buffer on FT221X pin MISO
    • receive buffer has data: MISO is LOW
    • receive buffer is empty: MISO is HIGH
    • usage: wait for MISO LOW before a read
  • reflect status of transmit buffer on FT221X pin MIOSIO[0]
    • transmit buffer is full: MIOSIO[0] is LOW
    • transmit buffer has room: MIOSIO[0] is HIGH
    • usage: wait for MIOSIO[0] HIGH before a write
• Dev-kit hard reset:
  • FT221X pin CBUS3 connects to the microcontroller RESET pin
  • USB host drives CBUS3 LOW to hard reset the dev-kit

Definition in file Usb-Hardware.h.