Working a lot with a microscope gives some challenges. You need to sit exactly in front of the microscope to get a good view. You get uncomfortable after a while. How to fix this? With the new VRScope!

The Altran Innovation Budget made it possible to buy a microscope (which you can see here).

For that we both (Guus and Marco) bundeled our budget to be able to buy this nice piece of equipment. Guus has an awesome private Makerspace where we both have 24/7 access to. All our shared equipment is placed here. The project idea is to attach a set of camera’s to the microscope and view the video stream through a Google kind of cardbox device. We also ordered the RPI Compute module, which makes it possible to make the device super light. Now we have to find the display to go with it. Normally you place a telephone in the cardbox, but this makes things kind of heavy. We want to make something with awesome resolution which is also light and comfortable.

Raspberry Pi Compute Module v3.0


MIPI CSI interface


The CSI (Camera Serial Interface) gives the possibility to connect a camera to the board. It is a standard from the MIPI organisation. Sorry to see it is a closed standard, but some documentation is leaking out, let’s find it.

Camera containing CSI transmitter
and CCI slave
Controller containing CSI receiver
and CCI master
CSI transmitter
Uni-directional
high speed link
CSI receiver
Data3+ (optional)
—>
Data3+ (optional)
Data3- (optional)
—>
Data3- (optional)
Data2+ (optional)
—>
Data2+ (optional)
Data2- (optional)
—>
Data2- (optional)
Data1+ (optional)
—>
Data1+ (optional)
Data1- (optional)
—>
Data1- (optional)
Data0+
—>
Data0+
Data0-
—>
Data0-
CCI slave
400 kHz Bi-directional
Control Link
CCI master
SCL
<---
SCL
SDA
<--->
SDA
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Besides the standard implementation there is sometimes GPIO to directly control things.

It looks like CSI-2 D-PHY is used looking at the wire configuration. In the beginning I thought that both CSI’s were identical, but that is not true. CSI1 has the full amount of connections (4 lanes), but the CSI0 only has 2 lanes available. this means that CSI0 has alimited amount of resolution possible.

CSI0 (D-PHY v1.x?)

CAM0_DP0, CAM0_DN0 Differential pairs
Data lane 0 .. 1
1.5 Gbit/s per lane
CAM0_DP1, CAM0_DN1
CAM0_CP, CAM0_CN Clock lane
CD0_SCL, CD0_SDA Camera Control (using CameraCommandSet CCS?)
Shared between camera and display
CAM0_IO0 2 GPIO’s
CAM0_IO1

CSI1 (D-PHY v2.0?)

CAM1_DP0, CAM1_DN0 Differential pairs
Data lane 0 .. 3
1.5 Gbit/s per lane
CAM1_DP1, CAM1_DN1
CAM1_DP2, CAM1_DN2
CAM1_DP3, CAM1_DN3
CAM1_CP, CAM1_CN Clock lane
CD1_SCL, CD1_SDA Camera Control (using CameraCommandSet CCS?)
Shared between camera and display
CAM1_IO0 2 GPIO’s
CAM1_IO1

The reason probably is that the SOC only supports this amount of lanes. Maybe in the future the SOC will support more lanes on both camera interfaces. Until that time I might need to use 2 RPI CM’s.

DSI Display Serial Interface


Ways to connect a display to the CM3 is to use a DSI screen. Why not try the iPhone 4S display. I have a 4S which is broken, I might be able to connect this screen, would be awesome! There should be a connector to get it to work, on the internet I found a link to a diverse number of different connectors. I am not sure yet which will fit. First I need to get my hand on the iPhone and see how many pins it has. Maybe find out the pin layout and go from there.

DSI0
DSI1

On the left you see the normal RPI, on the right you see the CM3, Camera adapter and Camera board (NoIR version). The CM3 setup will be a lot smaller, and lighter 😀

Bill of Material (2017-11-27):

Article ArticleNumber Amt Price € Total €
SM-4TP stereomicroscoop 7-45x SZM7045NT-STL2 1 695,00 695,00
Dimbare ledring voor microscopen LEDR60 1 49,00 49,00
Barlow lens 0.5x SM05 1 39,00 39,00
SubTotal Eleshop   1   783,00
Article ArticleNumber Amt Price € Total €
Raspberry Pi Compute Module 3 Development Kit KW-1783 1 224,95 224,95
Raspberry Pi NoIR Camera Board V2 – 8MP – Infrarood Camera KW-1703 2 29,95 59,90
Flexkabel voor Raspberry Pi Camera Board – 100cm RPI-FLXCBL100 2 4,95 9,50
SubTotal Kiwi Electronics B.V.       294,75
Total       1077,75
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iPhone displays


For the screen we need a high PPI value but we do not explicitly need the 16:9 ratio. I think the iPhone 4 screen is a nice place to start. Current iPhone display specs:

Phone Model Size Pixels Ratio PPI
iPhone 1st Gen/2G A1203 3.5″ 320 x 480 3:2 ~165
iPhone 3G A1241
iPhone 3GS A1303
iPhone 4 A1332, A1349 3.5″ 640 x 960 3:2 ~330
iPhone 4S A1387
iPhone 5 A1428, A1429 4.0″ 640 x 1136 16:9 ~326
iPhone 5c A1456, A1507, A1526,
A1529, A1532
iPhone 5s A1453, A1457, A1528,
A1530, A1533
iPhone SE A1662, A1723, A1724
iPhone 6 A1549, A1586, A1589 4.7″ 750 x 1334 16:9 ~326
iPhone 6s A1633, A1688, A1700
iPhone 7 A1660, A1778,
A1779, A1780
iPhone 8 A1863, A1905, A1906
iPhone 6 Plus A1522, A1524, A1593 5.5″ 1080 x 1920 16:9 ~401
iPhone 6s Plus A1634, A1687, A1699
iPhone 7 Plus A1661, A1784,
A1785, A1786
iPhone 8 Plus A1864, A1897, A1898
iPhone X A1865, A1901, A1902 5.8″ 1125 x 2436 19.5:9 ~458

Possible screens to connect to the RPI family:
http://nl.farnell.com/raspberry-pi/raspberrypi-display/raspberry-pi-7inch-touchscreen/dp/2473872

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