Hola de nuevo.
He probado a ejecutar "jtag" como root y ya no me da ese error, pero me sigue fallando:
# jtag
UrJTAG 0.10 #2007
Copyright (C) 2002, 2003 ETC s.r.o.
Copyright (C) 2007, 2008, 2009 Kolja Waschk and the respective authors
UrJTAG is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
There is absolutely no warranty for UrJTAG.
warning: UrJTAG may damage your hardware!
Type "quit" to exit, "help" for help.
jtag> cable usbblaster
Connected to libftdi driver.
jtag> endian big
jtag> detect
IR length: 5
Chain length: 1
Device Id: not supported (bit 0 was not a 1)
Error: Unable to detect JTAG chain end!
jtag>
Estoy un poco perdido, siguire buscango mas.
Gracias.