[ 01.11.2015 ] : The 1st of my dozen PCBs I designed over the holiday break arrived in yesterday’s mail. These designs fabbed out 12.26.2014 and arrived 01.20.2015. Cost was $3 and $5.
[ Micro USB Backdoor FT232HL ]
This board uses a FTDI USB 2.0 interface chip the FT232HL that I have not used before. My experience with the FTDI USB 1.0 chips has been great as they require very few components ( internal Oscillator and termination resistors ) but they are limited in data rates. I use them as standard serial converters at 921,600 baud. This project is to try and get a faster serial “Backdoor” interface into my FPGA designs. The FT232HL does require an external XO ( backside ) but promises to deliver a default 12Mbps UART over 2 wires using my existing FTDI cable 1×6 header connection that all of my FPGA boards already have. My FPGAs clock at 80 MHz, so sampling 12 Mbps should not be an issue. This should be 12x faster than my existing FTDI cable solution and require very little change in software, hardware or connections.
[ Micro USB FIFO FT232HL x16 ]
The x16 variant is basically the same design using the FT232HL, but pinned out to interface to my x16 “Nano Bus” that I now have standard on my Spartan3 and Spartan6 Nano FPGA boards. The FT232HL can be configured to use a “245 FIFO” interface mode of 8 data bits plus 8 control bits and transfer data at 40 MBytes/Sec. If Windows can keep up, this would be 320x faster than my existing 921,600 baud FTDI cable solution. A complication for this circuit is that the chip must be told to use the “245 FIFO” mode from an external PROM ( SOT23-6 ) that is configured via the FTDI configuration application.