INSTRUCTIONS
================================

# Building the B2xx FX3 Firmware

The USRP B200 and B210 each use the Cypress FX3 USB3 PHY for USB3 connectivity.
This device has an ARM core on it, which is programmed in C. This README will
show you how to build our firmware source

**A brief "Theory of Operations":**
The host sends commands to the FX3, our USB3 PHY, which has an on-board ARM
which runs the FX3 firmware code (hex file). That code translates commands into
SPI commands to/from the AD9361. The SPI lines run through the FPGA (bin or bit
file), where they are level-translated, and then head to the AD9361. Note that
the FPGA takes no action on these SPI lines. They are passive pass-throughs.

## Setting up the Cypress SDK

In order to compile the USRP B200 and B210 firmware, you will need the FX3 SDK
distributed by the FX3 manufacturer, Cypress Semiconductor. You can download the
[FX3 SDK from here](http://www.cypress.com/?rID=57990).

Once you have downloaded it, extract the ARM cross-compiler sub-directory from
the zip file and put it somewhere useful. The highest level directory you need
is `arm-2011.03/`.

Now that you have extracted the cross compilation toolchain, you need to set up
some environment variables to tell the B2xx `makefile` where to look for the
tools. These variables are:

```
    $ export ARMGCC_INSTALL_PATH=<your path>/arm-2011.03
    $ export ARMGCC_VERSION=4.5.2
```

Now, you'll need to set-up the Cypress SDK, as well. In the SDK, navigate to
the `firmware` directory, and copy the following sub-directories into
`uhd.git/firmware/fx3`: `common/`, `lpp_source/`, `u3p_firmware/`.

Your directory structure should now look like:

```
uhd.git/
       |
       --firmware/
                 |
                 --fx3/
                      |
                      --ad9361/             # From UHD
                      --b200/               # From UHD
                      --common/             # From Cypress SDK
                      --gpif2_designer/     # From UHD
                      --lpp_source/         # From Cypress SDK
                      --u3p_firmware/       # From Cypress SDK
                      --README.md           # From UHD
```


## Applying the Patch to the Toolchain

Now, you'll need to apply a patch to a couple of files in the Cypress SDK. Head
into the `common/` directory you just copied from the Cypress SDK, and apply the
patch `b200/fx3_mem_map.patch`.

```
    # cd uhd.git/firmware/common/
    $ patch -p2 < ../b200/fx3_mem_map.patch
```

If you don't see any errors print on the screen, then the patch was successful.

## Building the Firmware

Now, you should be able to head into the `b200/` directory and simply build the
firmware:

```
    $ cd uhd.git/firmware/fx3/b200
    $ make
```

It will generate a `usrp_b200_fw.hex` file, which you can then give to UHD to
program your USRP B200 or USRP B210.