Facedancer

Links

• http://travisgoodspeed.blogspot.be/2012/07/emulating-usb-devices-with-python.html
• http://blog.opensecurityresearch.com/2012/11/solder-time-facedancer11-and-goodfet41.html
• http://goodfet.sourceforge.net/hardware/facedancer11/

Merging Facedancer & R-Pi

Why?

Facedancer11 is a one-purpose version of the flexible GoodFET board.
It was well designed to move all the intelligence into the host controller, not in the embedded uC.
Facedancer11 hardware can be seen as:

 USBconn -- FT232RL -- MSP430F2618TPM -- MAX3420E -- USBconn

where the first two chips are only converting busses:

 USBconn -- FT232RL -- MSP430F2618TPM -- MAX3420E -- USBconn
         USB   <>   UART     <>       SPI   ...   (USB)

BoM view (excluding taxes, Farnell prices):

 USBconn -- FT232RL -- MSP430F2618TPM -- MAX3420E -- USBconn
 USBconn +  5.45€   +  13.03€         +  8.27€    +  USBconn

So 18.48€ to talk SPI over UART over USB while the Raspberry-Pi has natively SPI, hmmm.
Bus speed view: yes there is a kind of bottleneck there...

 USBconn -- FT232RL -- MSP430F2618TPM -- MAX3420E -- USBconn
        12MB/s      115200bauds       26MHz

Let's try to make a RPi extension board with only the MAX3420E. And to save a few cents and construction pain let's replace the USB connector by a USB cable from a cannibalized mouse. So:

                        RPI-MODA-256M -- MAX3420E -- USBcable

From a BoM point of view this becomes (depending on what you add to the RPi, nice casing etc):

                        RPI-MODA-256M -- MAX3420E -- USBcable
                        27.66€        +  8.27€

Bus speed view:

                        RPI-MODA-256M -- MAX3420E -- USBcable
                                      26MHz

And we get a fully autonomous facedancer which can be even powered over USB and controlled remotely

Schematics

TODO

x
x
P3  Vcc    P1 3v3 -- 0.1uF -- GND
P4  Vcc    P1 3v3 /
P5  GND \                      P
P6  GND /
x
x

x
P10 -RST                       P15-GPIO22
P11 SCLK
P12 -CS
P13 MISO
P14 MOSI
x
x

(P17 INT)
P18 GND
P19 GND
P20 -- 33 -- USB D-
P21 -- 33 -- USB D+
P22 Vcc -- 1uF -- GND
P23 Vcc
P24 USB VBUS -- 1uF -- GND

x
P26 XTal -- 18pF -- GND
P27 XTal -- 18pF -- GND
x
x
x
x
x

Code

#!/usr/bin/env python
# (C) 2013 Philippe Teuwen <phil at teuwen.org>

import spi
import RPi.GPIO as GPIO

class GoodFET:
    data=""
    def __init__(self, *args, **kargs):
        GPIO.setmode(GPIO.BOARD)
        # pin15=GPIO22 is linked to MAX3420 -RST
        GPIO.setup(15, GPIO.OUT, initial=GPIO.LOW)
        GPIO.output(15,GPIO.HIGH)
        spi.openSPI(speed=26000000)
    def __del__(self):
        spi.closeSPI()
        GPIO.output(15,GPIO.LOW)
        GPIO.output(15,GPIO.HIGH)
        GPIO.cleanup()
    def writecmd(self, app, verb, count=0, data=[]):
        if verb: # ignore all but R/W cmd
            return
        if isinstance(data,str):
            data = [ord(x) for x in data]
        data = tuple(data)
        data = spi.transfer(data)
        self.data = "".join([chr(x) for x in data])
    def serInit(self):
        pass