[flashrom] [PATCH] Add Olimex ARM-USB-TINY as an FT2232 SPI Programmer

[Pete Batard]

Hi Benjamin,

On 2011.06.11 18:47, Benjamin Henrion wrote:
> I own a JTAGkey Tiny, I am interested to test flashing an SPI BIOS
> chip with it, what should I do?
>
> The webpage says:
>
> "The Amontec JTAGkey2 can be used with flashrom for programming SPI
> chips. JTAGkey and JTAGkey-Tiny should work, if you add them to
> ft2232_spi.c (untested)."

The first thing to do will be to find the USB Vendor ID (VID) and 
Product ID (PID) of your device. This can usually be accomplished by 
plugging in your device and checking its properties (eg. by issuing the 
command 'lsusb' on Linux). The VID used by Amontec is expected to be the 
same as the one used by FTDI, hence 0x0403, so all you should have to do 
is find the PID.

Once you have these values, you should be able to duplicate the entries 
related to the JTAGKey in ft2232_spi.c, and add a new identifier for 
yours. Then after recompiling (you'll need libftdi installed), you 
should be good to go.

> Should I power the chip externally in 3.3v?

Yes you should. Both the Amontec and the Olimex based products related 
to ARM JTAG interfacing use a standard ARM JTAG pinout, that does not 
include provision for providing power.

An example of the full ARM JTAG pinout is provided in the entry for the 
ARM-USB-TINY [1]. VREF and VTARGET are used as input only (and are 
usually connected together), to adjust to the voltage being used by the 
target device, so unless your device has an additional port to provide 
power, the JTAG port alone will not do as a voltage source.

However, I found that providing power for SPI was really no trouble at 
all: all you need to do is pick up a couple of AA or AAA batteries, put 
them in serial, and you have the 3.0V DC you are after (anything close 
to 3V will do - it doesn't have to be exactly 3.3). If you have any 
remote lying around, that uses 2 AAs, all you have to do is open the 
battery compartment and stick 2 cables where the batteries make contact 
near the middle, since all the remotes I know have the battery 
serialization at the bottom.

The voltage source then needs to be split between the JTAGKey (JTAG 
VREF+GND) and your SPI target (SPI VCC+GND), but if the JTAGKey Tiny 
design is the same as the ARM-USB-TINY from Olimex, even that should be 
a no brainer, as VREF and VTARGET would be connected together, as well 
as all the ground lines. Therefore, you just have to connect the voltage 
source to the key, and you should be able to pull that voltage, from 
duplicated pins, into your SPI port.

Please let us know how your testing goes.

Regards,

/Pete

[1] 
http://www.flashrom.org/FT2232SPI_Programmer#Olimex_ARM-USB-TINY_and_related_devices