[Dprglist] Fwd: PAA5100JE Near Optical Flow SPI Breakout is now available at Pimoroni!

Murray Altheim murray18 at altheim.com
Tue Jun 8 16:24:59 PDT 2021

Hi Karim,

I'll be very interested in hearing how you and yours figure out the best way to
use these new sensors. I think overall they'll be very helpful to those wanting
some sort of optical odometry, or at least some kind of optical assist. As I
mentioned, even if it can't be used for truly accurate odometry over varied
surfaces it still might be very handy for driving in a straight line, or other
tricks we haven't even thought of yet.



On 9/06/21 9:34 am, Iron Reign wrote:
> Thanks Murray. Very helpful. I've ordered a brace of them. They're not in the Amazon store yet, so gotta wait on international shipping.
> On Tue, Jun 8, 2021 at 4:18 PM Murray Altheim via DPRGlist <dprglist at lists.dprg.org <mailto:dprglist at lists.dprg.org>> wrote:
>     Hi Karim,
>     I'll try to get the post, which is about half ready, posted ASAP, though I've
>     got a lot going on right now at home and work.
>     I think it's definitely worth a look. My initial play with it was using the
>     existing PMW3901 Python library, as suggested by the Pimoroni techs, and I'd
>     tested it out over nine different surfaces and with that library I found the
>     image complexity was clearly related to the measured velocity, but Pimoroni
>     updated their library, and while the update doesn't entirely eliminate that
>     issue, it's much less significant than before. I don't think you'll be able
>     to use the sensor solely to measure distance over significantly varied
>     surfaces with accuracy, but over a relatively constant surface I think it's
>     pretty good, within a few percent.
>     It outputs a simple stream of x,y values when moving, clearly on an interrupt
>     basis as that stream stops when the movement stops. I measured the 'x'
>     dimension (oriented as it was) over one meter and so long as I stayed on the
>     kind of surface that I calibrated it for the measurements were quite accurate.
>     An interesting notion might be to use the other axis with a PID controller to
>     travel in a straight line, as while dragging my little robot sled over the
>     test surface I'd get small 'y' values that could be used for course correction.
>     With the new Python library I think the minimum to maximum of the nine
>     surfaces I tested on (tile, wood floor, lawn, concrete, rug, etc.) varied by
>     something like 10-15%, but on any given surface the ten runs of my test
>     varied by only a few percent max, often less than 1%. Repeatable results.
>     It'd be possible to calibrate the sensor over different surfaces and switch
>     calibrations based on the surface if it were possible to detect the surface
>     type, possibly using a camera or spectrometer sensor like the Pimoroni
>     AS7262 that could detect color (which actually works pretty well, e.g.,
>     it's easy in my house to know the difference between my tile, wood and
>     carpet flooring by color). I've got a spreadsheet of results that will be
>     part of the review/blog post.
>     At £18.90 (US$26.75 / NZ$37) it's not cheap but I think worth a look, yes.
>     The only downside really, which was entirely predictable, is that its
>     operating range is 10-35mm, suitable for hanging underneath a small robot,
>     but not so much under say, a Mars rover, whose bottom is likely higher than
>     35mm. In that case the PWM3901 would be more suitable, but not necessarily
>     as accurate,
>     Cheers,
>     Murray
>     On 9/06/21 8:52 am, Karim Virani wrote:
>      > How about at least a teaser? Worth a look?
>      >
>      > On Tue, Jun 8, 2021 at 3:49 PM Murray Altheim via DPRGlist <dprglist at lists.dprg.org <mailto:dprglist at lists.dprg.org> <mailto:dprglist at lists.dprg.org <mailto:dprglist at lists.dprg.org>>> wrote:
>      >
>      >     Hi,
>      >
>      >     FYI, Pimoroni has finally announced stock availability on their new PAA5100JE
>      >     Near Optical Flow Sensor, which I'll be posting a review on hopefully soon.
>      >
>      >         PAA5100JE Near Optical Flow SPI Breakout
>      >         Detect motion of close-up surfaces with this Breakout Garden compatible
>      >         optical navigation breakout - great for floor tracking for ground dwelling robots!
>      > https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout <https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout> <https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout
>     <https://shop.pimoroni.com/products/paa5100je-optical-tracking-spi-breakout>>
>     ...........................................................................
>     Murray Altheim <murray18 at altheim dot com>                       = =  ===
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Murray Altheim <murray18 at altheim dot com>                       = =  ===
http://www.altheim.com/murray/                                     ===  ===
                                                                    = =  ===
     In the evening
     The rice leaves in the garden
     Rustle in the autumn wind
     That blows through my reed hut.
            -- Minamoto no Tsunenobu

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