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How to setup the board using only a usb cable

Beware! If you use this, you just need to have a usb cable plugged in.

Install jumpers and connectors as indicated in the figure below. Jumpers necessary are the white and the green ones.

Installation

Preparing Python

pip3 install pyftdi matplotlib numpy scipy

Installing iceprog to flash the fpga

iceprog is the software used to put the fpga on the flash storage on the board, which will be read by the fpga on boot. The easiest way is to :

sudo apt install fpga-icestorm

If this doesn’t work, then this may work:

sudo apt-get install libftdi-dev git gcc 
git clone https://github.com/cliffordwolf/icestorm.git
cd iceprog
make 
sudo make install

This will create and install the iceprog utility, used to flash the fpga program (bitstream).

FTDI rules.

Notes for Linux: Create a file /etc/udev/rules.d/53-lattice-ftdi.rules with the following line in it to allow uploading bit-streams as unprivileged user:

ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6014", MODE="0660", GROUP="plugdev", TAG+="uaccess"

This should solve usb access rules.

Setting jumpers

Put jumpers on the J23 header, only on Jumper2 and on "SPI FT if ON". See at the bottom of the page for the VGA connections.

Optional: connection for VGA

For this binary, you will need to connect VGA lines to the board, using the header close to the buttons (beware, this image should be rotated to align with the actual board silkscreen).

  • IO1_RPI = GREEN (color of your choice really)
    • A 270 Ohm R should be inserted in series with the line.
  • IO2_RPI = VSYNC
    • A 120 Ohm R should be inserted in series with the line.
  • IO4_RPI = HSYNC
    • A 120 Ohm R should be inserted in series with the line.
  • GND = GND

Beware, IO3 seems not to be working on this bin.

Below, and example of my connections with nice resistors.

Connect the usb cable

Check that the FTDI device is well created by typing:

dmesg

Programming it 

wget https://github.com/kelu124/un0rick/raw/master/usb/usb.bin
iceprog usb.bin

Using the python lib

In python

In essence, installing the module pip3 install un0usb before, or, to get a specific one:

wget https://github.com/kelu124/un0rick/raw/master/usb/python_lib/un0usb-0.2.6.tar.gz
pip3 install un0usb-0.2.6.tar.gz

Then, from a python shell, you can initialise the board with the following code.

import un0usb as USB # neeeds `pip3 install un0usb` before
fpga = USB.FpgaControl('ftdi://ftdi:2232:/', spi_freq=8E6) # init FTDI device 
fpga.reload() # reload configuration
fpga.reset() # reset fpga

file = fpga.stdNDTacq() # Running a standard NDT acquisition
plot = USB.FView() # Opens a viewing object
data = plot.readfile(file) # plots it

After the fpga.reset() command, D7 should be starting to blink.

Managing the VGA output

If not jumper is put on Jumper2, you should start having on the VGA output a picture of what is happening on the board in real time. The board registers and parameters can be set via USB, but acquisition triggers is managed by the board itself, not allowing you to read from the buffer.

LARGE IMAGE, BEWARE

If a jumper is set on Jumper2, the display with only display the latest acquisition, and the board will be fully controlable via USB, including the option to read from the board RAM.

Result

The full log is here.

Going in deeper details

###

The lib and examples should be self sufficient. However, you can go at a deeper level by exploring the un0usb library.

Pulser control

To control the waveform, one would set the fpga.csr.ponw, fpga.csr.interw and fpga.csr.poffw, that are respectively integers for setting the width (timing) of the pulse, width of a relaxation period before damping, and then duration of damping. Unit are (1/128us).

The fpga.csr.initdel register is the delay between the beginning of the acquisiton and the pulse.

fpga.csr.initdel = InitDel
fpga.csr.ponw = PONWidth
fpga.csr.interw = INTERWidth
fpga.csr.poffw = PDAMP

Below is plotted amplitude of an echo as a function of the fpga.csr.ponw for a 4MHz transducer. One sees that a setting at 16 provides most

(See full experiment here).

Gain and acquisitions

And do acquisitions with acq_res = fpga.do_acquisition(acq_lines=32, gain=gain, double_rate=True) which will return an array of acq_lines acquisitions, of length 256us at 64Msps. double_rate=True provides a half clock offset to odd lines, so that one can interleave two subsequent acquisition to have, in a fixed setting, a 128Msps acquisition.

The gain setting is an array of integers, of length 32, that can range from 0 to 1023, controlling gain for each of the 32 8us-segment of acquisition within the 256us line.

Other registers

  • fpga.csr.led3 = 0 sets LED3 off. led1, led2, led3 are possible, can be set to 0 or 1.
  • fpga.csr.topturnX reads input 1 to 3 on the input header.
  • fpga.csr.jumperX reads jumper 1 to 3 close to the programming jumper.
  • fpga.csr.outXice writes/reads output 1 to 3.
  • fpga.csr.nblines = acq_lines - 1 is the register controlling the number of lines acquired.
  • fpga.csr.dacout reads the DAC/TGC/VGA level outside of acquisitions.
  • fpga.csr.acqstart = 1 to start the acquisition
  • fpga.csr.drmode = int(double_rate) triggers the interleaving mode.
  • fpga.csr.acqstart = 1 to start the acquisition
  • fpga.csr.acqdone is equal to 0 during acquisitions.
  • fpga.csr.author reads the ID of the author of the binary.
    • 1 : kelu124
  • fpga.csr.version reads the ID of the author’s binary.
    • 1 The current binary version

Don’t hesitate to improve the gateware and push more here.

Example of acquisitions

Raw signal, with DAC

The signal is in blue, the gain levels are in green. Here there are 32 visible steps, of 8us each.

Detail of an echo

Interleaved acquisiton mode = ON

Doublign acquisition speed (yellow and red dots below)