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Poll: How much would you be willing to pay for a Neo900 (complete device) with TI DM3730 1GHz/512M-RAM/1GB
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How much would you be willing to pay for a Neo900 (complete device) with TI DM3730 1GHz/512M-RAM/1GB

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#2761
Originally Posted by wpwrak View Post
Of course, two parameters are still a very course approximation of the actual spectrum. But you'd probably need serious lab equipment to determine that. (A comparison between two LEDs would be easier, though, since any systematic errors of the test setup would affect both measurements in the same way. Joerg suggested using a prism. You'd still need a proper lab setup, though, if only to make sure the geometry doesn't change between tests.)

- Werner
There's a nice instruction on how making a spectrometer out of cardbox and a DVD-R as a diffraction grating:
https://publiclab.org/sites/default/...ni-spec3.8.pdf
Using a good camera, it seems possible to get surprisingly good results from this:
https://publiclab.org/notes/cfastie/...ometer-testing

So, if you're a bit into that stuff, it could be fun to build one (I feel a bit tempted to do this myself now ).

But the most pragmatic solution probably is this: get a colorchecker chart, take a raw image on the n900 with fcamera using LED illumination, compare using a standard white balance setting, pick the LED closest to the original one. Just from the spectrum, the effects of different LEDs could be a bit hard to predict, because of the color filter array on the sensor and its transmission function.
 

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#2762
maybe our tech affine community members want to contribute to a recent discussion Werner and I do about the HackerBus USB connection? Concerns are about mechanical stability of the 3pin header (Mill-Max 851-43-003-30-001000) as well as about signal integrity with a unterminated stub of >5mm length (from the header springs) on DP/DN. Alternatives we look into: Zebra strips (http://www.abatek.com/en/products/connectors.html) or pogopins on user's extension board (http://www.digikey.com/product-searc...4-11-0&stock=1)

/j
 

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#2763
Jolla, take note... THIS is how you do openness!
 

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#2764
enyc contributed great inspiration (IRC) and Werner revisited pinmux and we plan to come up with a dedicated USB interface on HackerBus primary connector (2 GPIO_x function reassignment). The OTG USB will have landing zone pads for pogopins mounted on user circuit, instead of that 3-pin SMT connector. Our recommendation is to leave OTG alone and rather use the dedicated USB host interface on hackerbus, for sake of less conflicts with original purpose of the OTG interface
Comments solicited

[edit] revised HB main connector pin assignment:
Code:
VBAT_RAW | VBAT_RAW
USB_HB_DP|USB_HB_DM
         GND   |  GND      
  NFC_GND | NFC_ANT
         GND   |  GND 
VBUS_OTG | VBAT_SWITCHED
GPIO_d/3V3 | GPIO_c
      GPIO_b | GPIO_a
   UART_TX | UART_RX 
 UART_CTS | UART_RTS
/j

Last edited by joerg_rw; 2016-01-27 at 19:54.
 

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#2765
Originally Posted by wpwrak View Post
Great, thanks a lot !

I currently have my eyes set on the L130-5780002011001 with 5700 K and a minimum CRI of 80%. CRI is something new I found:
https://en.wikipedia.org/wiki/Color_rendering_index

Of course, two parameters are still a very course approximation of the actual spectrum. But you'd probably need serious lab equipment to determine that.
Is this flash color still an active issue? The comments are 2 months old.

I have both an original N900 and an x-rite i1Pro2 spectrophoto/radiometer. It should be able to read the flash color as detailed spectrum curve, and the dominant color in K.

Is there still interest in this, particularily by the persons who select the flash components? Please give feedback here on the thread or by email in case that such a measurement is still useful at this point.
 

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#2766
Originally Posted by jetmarc@hotmail.com View Post
Is there still interest in this, particularily by the persons who select the flash components?.
Yes, of course. Highly appreciated, many thanks for helping with this

/j
 

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#2767
http://neo900.org/stuff/joerg/4_BB-xM/
Thanks to xes for moderation!
Let's see if mouser actually can ship the ordered 6 board in 3 days - ordered a 20 months ago
 

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#2768
Originally Posted by joerg_rw View Post
Yes, of course. Highly appreciated, many thanks for helping with this

Ok I did this today, and this is what I got.

Target: My N900 was bought some 3-6 months after market introduction. The aparture of the camera/flash unit had a blue-colored tint on the edges, which was neutralized with black ink. To measure the flash color, I turned on the "flashlight" mode. I am not sure if this is a low current mode and if the current influences the color, but it is easier to measure. Let me know when this is not good enough.

Tools: x-Rite i1Pro2 and ArgyllCMS 1.8.3

Measurement 1: spotread -a -N

For this measurement I used the ambient light adapter and had the phone shining into the sensor from a distance of maybe 2 cm.

Code:
 Result is XYZ: 10381.329780 11168.856635 10074.093410, D50 Lab: 542.634253 -29.250888 -29.109195
 Ambient = 11168.9 Lux, CCT = 5675K (Delta E 9.687946)
 Suggested EV @ ISO100 for 11168.9 Lux incident light = 12.1
 Closest Planckian temperature = 5403K (Delta E 8.488890)
 Closest Daylight temperature  = 5517K (Delta E 4.974792)
 Color Rendering Index (Ra) = 70.1 [ R9 = -37.7 ]
 Television Lighting Consistency Index 2012 (Qa) = 48.5
Measurement 2: illumread -v -N

This measurement consists of 3 individual measurements. The first is of the flash shining directly into the sensor, and I used the a similar setup as before (ambient light adapter, approx 2 cm). The second measurement is reflected from paper, and I used vanilla office printer paper and an angle of 45 degrees approx. The third measurement is the paper color itself, and I use the normal spot reading setup. The last two measurements are supposed to clue about the UV contents of the light source.

Code:
SPECT  

DESCRIPTOR "Argyll Spectral power/reflectance information"
ORIGINATOR "Argyll CMS"
CREATED "Sun Mar  6 02:25:02 2016"
SPECTRAL_BANDS "45"
SPECTRAL_START_NM "290.000000"
SPECTRAL_END_NM "730.000000"
SPECTRAL_NORM "1.000000"

NUMBER_OF_FIELDS 45
BEGIN_DATA_FORMAT
SPEC_290 SPEC_300 SPEC_310 SPEC_320 SPEC_330 SPEC_340 SPEC_350 SPEC_360 SPEC_370 SPEC_380 SPEC_390 SPEC_400 SPEC_410 SPEC_420 SPEC_430 SPEC_440 SPEC_450 SPEC_460 SPEC_470 SPEC_480 SPEC_490 SPEC_500 SPEC_510 SPEC_520 SPEC_530 SPEC_540 SPEC_550 SPEC_560 SPEC_570 SPEC_580 SPEC_590 SPEC_600 SPEC_610 SPEC_620 SPEC_630 SPEC_640 SPEC_650 SPEC_660 SPEC_670 SPEC_680 SPEC_690 SPEC_700 SPEC_710 SPEC_720 SPEC_730 
END_DATA_FORMAT

NUMBER_OF_SETS 1
BEGIN_DATA
0.00490145 0.00490145 0.00490145 0.00490145 0.00490145 0.00490145 0.00490145 0.00490145 0.00490145 0.00490145 0.00177026 0.00431980 0.0214035 0.145008 0.653737 2.039361 3.369266 1.993886 0.779962 0.403550 0.404197 0.686909 1.171644 1.634942 1.913347 2.028934 2.063459 2.059977 2.020874 1.931819 1.784170 1.599621 1.397492 1.196757 1.008129 0.835002 0.681009 0.547155 0.433853 0.336795 0.259777 0.201203 0.157002 0.124581 0.104186 
END_DATA
This file can be examined using specplot:

Code:
Type = File 'test2' spect 0 [Black]
XYZ = 0.931246 1.000000 0.900338, x,y = 0.328878 0.353159
D50 L*a*b* = 100.000000 -5.762902 -5.919376
CMYV density = -0.144735 -0.240183 -0.112879 -0.219696
CCT = 5650.126305, VCT = 5387.721842
CDT = 5651.454724, VDT = 5501.851749
CRI = 70.1 [ R9 = -37.0 ]
TLCI = 48.5
CIEDE2000 Delta E = 1.901252
The last command also creates a plot image: base64 -d > plot.png

Code:
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AAAASUVORK5CYII=
Hopefully this helps for your project. I really liked the N900. To me it was a little laptop in my pocket, with SSH openvpn and rdesktop. Now I am on Android and I really miss these things. On Android, you can only do what you are supposed to do (much like on the N9, which ended the the drawer after just 2 days). Sometimes I still use the N900 as laptop replacement on short trips, and I wish someone would offer a modern device for developers.
 

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#2769
@jetmarc
Many thanks! This is extremely helpful.

re flashligt mode: yes that is with reduced LED current, the LEDs would burn out at full power used during flashing for longer than 1 or 2 seconds. It's also known that there been a greenish hue aberration in iirc macro mode before iirc PR1.2 drivers.

I guess the results from your test are good enough to determine which color binning we should use for the LEDs, however if it doesn't cause too much of a hassle to you, a short reference colortemp test with flash mode would be welcome - to extend the flash duration you should cover the cam lens.

Again many thanks
cheers
jOERG
 

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#2770
Originally Posted by jetmarc@hotmail.com View Post
Ok I did this today, and this is what I got.
Thanks a lot, this is great data ! A question about interpreting the color temperatures:

Code:
 Ambient = 11168.9 Lux, CCT = 5675K (Delta E 9.687946)
 Closest Planckian temperature = 5403K (Delta E 8.488890)
 Closest Daylight temperature  = 5517K (Delta E 4.974792)
I realize that there is a lot to know about light that I didn't even know I didn't know ;-) Of these three, would "CCT" (approx. 5700 K) be the one that corresponds to the CCT parameter of the LED ?

In the L130 series, we get to choose between nominal CCT values of 5000 K and 5700 K (or values further out). Each also comes with fairly large tolerances, e.g., 5500 K would still seem to be within the "best" tolerance bin of the nominally 5700 K LED.

The color binning is shown in figure 16 of
http://www.lumileds.com/uploads/461/DS209-pdf

Code:
 Color Rendering Index (Ra) = 70.1 [ R9 = -37.7 ]
I'm very happy about this one. I had been a bit worried about the CRI, since the best we can get at 5700 K is 80%, and I wasn't sure if the "missing" 20% would be a problem. But this is actually even one step better than the original then.

Code:
The last command also creates a plot image: base64 -d > plot.png
Thanks a lot ! The curve does indeed look like the 5700 K curve of the L130.

Again, thanks a lot ! It's always better to have solid data to rely on than guesswork, no matter how sophisticated.

- Werner
 

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neo900, thank you!

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