doc: Add doc for buspirate programmer

Doc migrated from the wiki page:
https://wiki.flashrom.org/Bus_Pirate

Change-Id: I5a57f08ea3fce0c78d73aa61b85ff7b0cff450b8
Signed-off-by: Anastasia Klimchuk <aklm@flashrom.org>
Reviewed-on: https://review.coreboot.org/c/flashrom/+/83471
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Reguera Garcia (Dreg) <regueragarciadavid@gmail.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

doc/supported_hw/supported_prog/buspirate.rst

@@ -0,0 +1,78 @@
+==========
+Bus Pirate
+==========
+
+The `Bus Pirate <http://dangerousprototypes.com/docs/Bus_Pirate>`_ is an open source design
+for a multi-purpose chip-level serial protocol transceiver and debugger.
+flashrom supports the Bus Pirate for `SPI programming <http://dangerousprototypes.com/docs/SPI>`_.
+It also has `SPI sniffing <http://dangerousprototypes.com/docs/Bus_Pirate_binary_SPI_sniffer_utility>`_
+functionality, which may come in useful for analysing chip or programmer behaviour.
+
+They are available for around US$30 from various sources.
+
+Connections
+===========
+
+The table below shows how a typical SPI flash chip (sitting in the center of the table)
+needs to be connected (NB: not all flash chips feature all of the pins below, but in general
+you should always connect all input pins of ICs to some defined potential (usually GND or VCC),
+ideally with a pull-up/down resistor in between). Most SPI flash chips require a 3.3V supply voltage,
+but there exist some models that use e.g. 1.8V. Make sure the device in question is compatible
+before connecting any wires.
+
+*NB: Some rather rare SPI flash chips (e.g. Atmel AT45DB series) have a completely different layout, please beware.*
+
++----------------------+------------+------+---------------------------------+------+------------+-----------------------------+
+|  Description	       | Bus Pirate | Dir. | Flash chip			     | Dir. | Bus Pirate | Description		       |
++======================+============+======+===+===========+=============+===+======+============+=============================+
+| (not) Chip Select    | CS	    | →	   | 1 | /CS	   | VCC	 | 8 | ←    | +3.3v	 | Supply		       |
++----------------------+------------+------+---+-----------+-------------+---+------+------------+-----------------------------+
+| Master In, Slave Out | MISO	    | ←	   | 2 | DO (IO1)  | /HOLD (IO3) | 7 | ←    | +3.3v	 | (not) hold (see datasheets) |
++----------------------+------------+------+---+-----------+-------------+---+------+------------+-----------------------------+
+| (not) Write Protect  | +3.3v	    | →    | 3 | /WP (IO2) | CLK	 | 6 | ←    | CLK	 | The SPI clock               |
++----------------------+------------+------+---+-----------+-------------+---+------+------------+-----------------------------+
+| Ground	       | GND	    | →	   | 4 | GND	   | DI (IO0)    | 5 | ←    | MOSI	 | Master Out, Slave In        |
++----------------------+------------+------+---+-----------+-------------+---+------+------------+-----------------------------+
+
+Usage
+=========
+
+::
+
+  $ flashrom -p buspirate_spi:dev=/dev/device,spispeed=frequency
+
+Example::
+
+  $ flashrom -p buspirate_spi:dev=/dev/ttyUSB0,spispeed=1M
+
+Troubleshooting
+===============
+
+In case of problems probing the chip with flashrom - especially when connecting chips
+still soldered in a system - please take a look at the doc :doc:`/user_docs/in_system`. In-system programming is often possible
+**only as long as no other devices on the SPI bus are trying to access the device**.
+
+Speedup
+=========
+
+A beta firmware build exists, to speed up the buspirate.
+`See this post on dangerousprototypes.com <http://dangerousprototypes.com/forum/viewtopic.php?f=40&t=3864&start=15#p41505>`_
+
+See also: http://dangerousprototypes.com/docs/Bus_Pirate#Firmware_upgrades
+
+Images
+==========
+
+Bus Pirate v3, front.
+
+.. image:: Buspirate_v3_front.jpg
+
+Bus Pirate v3, back.
+
+.. image:: Buspirate_v3_back.jpg
+
+Recovering a bricked Lycom PE-115 88SE8123 PCIe to SATA adapter using flashrom and a Bus Pirate - power to the
+PE-115 is supplied by a PC. The test probes of the bus pirate are attached directly to the SOIC Atmel AT26F004 SPI flash chip.
+The other test clip is connected to GND on another device for convenience (easier than getting yet another clip onto a SOIC device).
+
+.. image:: Lycom-pe115-flashrom-buspirate-2.jpg

doc/supported_hw/supported_prog/index.rst

@@ -15,5 +15,6 @@ Patches to add/update documentation, or migrate docs from `old wiki website <htt
 .. toctree::
     :maxdepth: 1
 
+    buspirate
     dummyflasher
     serprog/index