Ftdi
Ok for programming electronics I got myself an ftdi chip buying this package. Now want to be able to invert the TX/RX/... signals so I can get some experiments working that I have in this book.
To do this we have to re-program the device's eeprom.
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read the eeprom
To read the EEPROM of the ftdi, use the software ftdi_eeprom.
- download the software
wget http://www.intra2net.com/en/developer/libftdi/download/ftdi_eeprom-0.3.tar.gz
- unpack it
tar xvzf ftdi_eeprom-0.3.tar.gz cd ftdi_eeprom-0.3
- build it
./configure && make -j4 && make install
- find out your ftdi's serial ID:
hwinfo --usb [...] Serial ID: "A7006Ys2" [...]
- configure ftdi_eeprom to use your serial id:
sed -i "s/^serial=.*/serial=\"A9VQ459E\"/" example.conf
- read your chip's eeprom:
ftdi_eeprom --read-eeprom example.conf
- find the file name where the eeprom is stored in:
ls -ltr [...] -rw-r--r-- 1 root root 128 Dec 15 12:59 eeprom.new
- verify that it is really an eeprom
# hexdump -C eeprom.new 00000000 00 40 03 04 01 60 00 00 a0 2d 08 00 00 00 98 0a |.@...`...-......| 00000010 a2 20 c2 12 23 10 05 00 0a 03 46 00 54 00 44 00 |. ..#.....F.T.D.| 00000020 49 00 20 03 46 00 54 00 32 00 33 00 32 00 52 00 |I. .F.T.2.3.2.R.| [...]
Re-program the eeprom
To re-program the eeprom, better read it before and have a backup.
- download the ftd2xx library http://www.ftdichip.com/Drivers/D2XX.htm
- download http://svn.icmb.utexas.edu/svn/repository/trunk/zpub/sdkpub/usbkey_dlpd/macosx/d2xx/Samples/EEPROM/write/main.c
- compile it using
gcc -o write main.c -L/root/Downloads/release/build/x86_64/ -lftd2xx -lpthread -ldl -lrt -Wl,-rpath,/usr/local/lib
- remove the ftdi_sio driver
modprobe -r ftdi_sio
- disconnect all other FTDI chips
- call the program to re-write the device's eeprom:
./write
understand the eeprom's bits
Using the program ftdi_eeprom I can read the 128 bytes of user's eeprom from the FTDI RS232R chip. Using the "write" command compiled above I can change single values like InvertTXD in the eeprom. So let's set all Invert values to 0x00. The Invert values are:
InvertTXD InvertRXD InvertRTS InvertCTS InvertDTR InvertDSR InvertDCD InvertRI
Now I modify main.c so that all Invert values are 0x01, compile and run it and get eeprom-all1 via ftdi_eeprom. Then I modify main.c so that all Invert values are 0x00, compile and run it and get eeprom-all0 via ftdi_eeprom. Then I use the cmp to find out which values have changed:
# cmp -l eeprom-all0 eeprom-all1 12 0 377 127 107 273 128 176 175
Indeed, byte 12 is 00h in eeprom-all0 and FFh in eeprom-all1. Besides, the last two bytes of the 128 bytes-file seem to contain a checksum, they are different as well.
