Serial communication via USB

1. USB-to-UART bridge (UART mode)

(1) Setup

  • Host: Linux PC, Ubuntu 14.04, ftdi_sio driver.
  • Target: FTDI FT232H.
  • Baud rate: 12 M.

um232h-loopback

(2) Loopback test result: 

  • round-trip time of 128 bytes: 1.48 ms  —> 0.173 Mbaud (= 1.38 Mbits/sec)

 

2. USB-to-FIFO bridge (asynchronous FIFO mode)

(1) Setup

  • Host: Linux PC, Ubuntu 14.04, libftdi 1.2 user-space driver.
  • Target:  FTDI FT2232H + Xilinx FPGA. 
  • Baud rate: 8 M.

ft2232h-flashlink

(2) Loopback test results :

  • round-trip time of 128 bytes  with 25 MHz FPGA clock: 0.13 ms  —> 1.97 Mbaud  (= 15.8 Mbits/sec)
  • round-trip time of 1530 bytes with 25 Mhz FPGA clock: 0.79ms —> 3.87 Mbaud (= 31.0 Mbits/sec)
  • round-trip time of 1530 bytes with 50 MHz FPGA clock: 0.48ms —> 6.38 Mbaud  (= 51.0 Mbits/sec)