• Night sky

    kelu12409/01/2018 at 13:49 0 comments

    Some more tests with a probe.. this time from kretz technik. Raw acquisition yield interesting signals.. Doesn't it look like a night sky ?

    The spectrum seems to contain good ultrasound (with a fair dose of noise) - the signal is between the blue lines, between 2.2MHz and 4.2MHz:

    Which yield a classical wirephantom image.

    See more on the notebook -- https://github.com/kelu124/echomods/blob/master/matty/20180901a/20180901a-Client.ipynb

  • Doubling the speed, to 128Msps

    kelu12408/14/2018 at 21:54 0 comments

    Breaking the wall of sound! un0rick can sample at 64Msps but ... one can offset the start of an acquisition by half a cycle. In practice, it means one can do two acquisitions, with one delayed by half a cycle, and interleave the two series. In practice: getting 128Msps acquisition speed!
    In picture, it seems quite nice. The signal is loud and clear!

    And notebook at https://github.com/kelu124/echomods/blob/master/matty/20180814a/20180814a-Server.ipynb . Some improvement on the lib too, not perfect yet but someday better!

  • Working with classes / calibration of TGC

    kelu12407/22/2018 at 12:56 0 comments

    Objectives

    The objective of this experiment is to check :

    1. If class-oriented library works
    2. The TGC functionning, and its calibration
    3. Have fun introducing new class functions

    Resources

    Results

    Type of signal

    Curve of the gain

    Impact of gain on noise

    FFT - content of such a line

  • Production: validated

    kelu12405/23/2018 at 21:10 0 comments

    The good news is that I've just tested the production version and it runs fine. Images of the wirephantom look good (full doc):

    Now working on the data format, and, in anticipation of the first runs, I've started working on the documentation, including some nice visuals:

    What do you think?

  • Comparing modules and fpga board

    kelu12404/17/2018 at 20:35 0 comments

    Let's compare the acquisitions with the modules compare to the un0rick board. At a reduced speed for the un0rick, the acquisitions are quite comparable, showing similar acquisitions at 21Msps and 22.5Msps.
    Blue is from the raspberry board, red from un0rick.Now, going on the details of the acquisitions. we see that the level of acquisitions are higher (which is normal as the range of the un0rick gets data on 10bits, whereas the pHAT is on 9 bits).
    Moreover, the last acquisition, at ~120us, appears quite nicely with un0rick, whereas it is off the radar on the modules.

    One can also see that the level of noise has improved by a factor of 4.. or more.

    But I'd need to be more rigourous to get precise numbers =)

    Log as usual is available.

  • Time gain compensation - check

    kelu12404/08/2018 at 21:35 0 comments

    Ultrasounds, traveling in the medium they image, are attenuated by the very same medium and the further they progress, the faintest the echo comes back.

    In order to compensate for this attenuation, the echoes are usually amplified by by a variable gain which renormalize these echoes.

    The plots below represent in blue, unsimplified signals, and, in green, the amplified signal, with a gain shifting from 0% to 100% in 200us. It seems that makes the echoes great again =)

    More in the log.

  • Retroengineering an ultrasound probe - part 1/X

    kelu12403/18/2018 at 20:57 0 comments

    I just got an interesting mechanical probe, a Bard Site Rite - piezo at 7.5MHz. The plug is quite simple, and digging into the cable yields 2 pairs of cable, one coax, a bigger cable with two "big" cables. I've made sure it's a mechanical probe. The aim is to try and see if I can connect it to my board and get an image.

    Good point for this probe is that it unscrews nicely.

    and even better, it has changeable heads!

    I assume two pairs of cables are for motors / actuators, coax is for the signal coming back (hence the bead). But how can I see that on the pins above?

    Going to search for the reference manual and other resources. I'd rather not unscrew the head yet!

    To be continued... possibly with a corresponding patent... Electromagnets?

  • Progressing with the signal acquisitions

    kelu12402/27/2018 at 22:07 0 comments

    Some good news again =)

    I got to better control pulses (I need to really read more carefully  datasheets), got acquisitions at 64Msps, really looking good, and got some (badly formed at the moment) images!

    Acquisitions - going to specs at 64Msps. Thanks David =)

    Pulser: getting 200ns wide 75V pulses (blue is the pulse with a piezo on, in yellow is the 'damping' control signal.

    Getting some images from a "damaged" probe

    More on the log!

  • Getting great results

    kelu12402/24/2018 at 19:43 3 comments

    That's moving forward! I'm getting some results with the following setup - using a piezo with a fixed distance, and a pulser at 25V.

    Getting nice echoes (x-label in us)

    The gain control works as well =)

    and the FFT looks relatively clean!

  • More hacks

    kelu12402/11/2018 at 22:47 0 comments

    I needed to replace some elements, some stuff is erratic, but hey, I've been able to set up all registers, run the analog part, and control the DAC gain.  I (just) need to run the ADC now, the fpga still thinks s.he's not working ;)

    Some pulse control works, and pulses too! With a 10x probe, on a 25V pulse

    Next step.. digitalization. More on the log.