Spider ;)

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Spider ;)

Postby Demmo » Wed May 20, 2009 7:40 am

Hi,
I'd like to introduce my.. uhmm.. spider :lol:
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I want to interface n9500 camera with ARM microcontroller for onboard vision system - I don't have any robot (yet), neither "brain" board but here are my first steps with the camera. First of all I've bought this cam because it was very cheap - 5zl which is about 1,14euro + shipping cost c.a. 1euro ;) So it wouldn't be a disaster if I just screw it up :mrgreen: All I have found about this cam are n9500 schematics where the cam connector pinout is described and.. that't all :D no datasheet = more fun :lol:
Pinout implies parallel 8-bit data bus and I2C/TWI interface for configuration. I have studied some other cameras datasheets and registers are different so there is no always-used standard :roll:

Original 20-pin connector was too small to solder 20 wires (I don't have the slot yet for simple connecting it to board - soldering the slot to PCB would be hundred times better and easier than making "spider-connection" :roll: ) so first decision - chop off the elastic tape containing connector...

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Fortunately there are pads underneath :) So far so good ;)

I have used the thinest wires I had but anyway soldering them to the cam module was pain in the ass :roll:

Image

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My ARM eval board with goldpins added (originally there are only pads without pins) and cam with "new" 20-pin connector ;) I have to build power-supply circuits because cam requires 2.8 and 1.8V so I have to reduce 3.3V available onboard

Image
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
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Re: Spider ;)

Postby Noodle » Wed May 20, 2009 10:37 am

How does the cam work as an I/O device with the microcontroller? Interesting project.
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Re: Spider ;)

Postby Demmo » Wed May 20, 2009 1:07 pm

I assume that on 8-bit data bus pixels are clocked out one by one and pixel position on screen (actually on photo-sensitive matrix) is synchronized by HSync and VSync signals - the same way as image is displayed on LCD without controller. There are input pins Dclk & Extclk so I assume that Extclk is clock for internal controller and Dclk is for data clocking out - faster Dclk should cause higher fps
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
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Re: Spider ;)

Postby Matt Denton » Wed May 20, 2009 9:17 pm

From what I understand of CMOS/CCD cameras, (whihc isn't much) is that they require a very high data bandwidth and as such require some kind of FPGA to interface to them??
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micromagic systems ltd
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Re: Spider ;)

Postby Demmo » Thu May 21, 2009 6:45 am

I think you are partially right Matt ;) Partially because I assume it relates to the sensor inside and it's (probably) because of lots of conversions needed starting from analog signal measurement, going through color interpolation (from current cell and neighbour photo-cells) and ending on formatting data to YUV or RGB format. Here is a very nice picture:

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Originally you don't have full color info on a pixel and it has to be interpolated etc.

On n9500 schematics the camera is connected directly (through resistors and capacitors) to TI's OMAP processor I/Os. I don't believe that IC which works at 150MHz (not sure now) and has to handle with LCD, GSM modules etc etc dedicates its full operational power to camera module ;)

If there is an option to communicate via I2C/TWI for configuration there must be a controller onboard. And if there is a controller working with your config it means it handles all these calculations and you get properly converted pixel data on data bus 8-)
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
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Re: Spider ;)

Postby Demmo » Thu May 21, 2009 9:35 pm

lol, tie.. first success and first defeat :D

the good thing is that I have prepared a cable connecting my 2 boards and it works (cable) - another spider :D I had to reorganize 34pin connector to 20pin one including the fact that port pins are placed very chaotically on LMs board and not all of them are used to interface with cam. Here is a pic - a little bit scary ;)

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the bad thing is that my conception of decreasing voltage level by use of diode totally collapsed :roll: I assumed that I would get 0.7V drop on each diode so by using one I will get 3.3-0.7=2.6V and by using two I will get 3.3-1.4=1.9V which is pretty close to my needs - rubbish :lol: It seems I have some very low drop diodes and when I measure voltage after second diode I get c.a 3.1V :lol:
yes, I know that this conception stinks and this is not the way it should be done but that was a quick try because I don't have any voltage regulator for 2,8 nor 1,8V... anyway I'll have to get one :roll:

Image
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
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Re: Spider ;)

Postby Matt Denton » Fri May 22, 2009 3:53 pm

Demmo wrote:I assumed that I would get 0.7V drop on each diode so by using one I will get 3.3-0.7=2.6V and by using two I will get 3.3-1.4=1.9V which is pretty close to my needs - rubbish It seems I have some very low drop diodes and when I measure voltage after second diode I get c.a 3.1V


The voltage drop of the diode will vary slightly depending on the load. :)
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micromagic systems ltd
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Re: Spider ;)

Postby Demmo » Fri May 22, 2009 7:31 pm

this is the point where my weak theory meets practice ;) I can't predict the load so I have to use voltage regulator anyway - that would be the safest solution for cam. I don't want to burn it off on first attempt.. maybe on second or third :lol:


[EDIT]
PROJECT TEMPORARILY SUSPENDED. There is an interest in my house management system which is much more important for me so cam has to wait 8-)
[/EDIT]
Demmo
btw. sorry for my english :P I should educate more ;) :lol:
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