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+++ b/bg_cnano/11sensor_assembly.md
@@ -10,4 +10,143 @@ parent: Build guide - Charybdis Nano
 1. TOC
 {:toc}
 
-// TODO
\ No newline at end of file
+
+
+# Preparing the 3d holder assembly
+## Top housing - screw inserts
+
+![](../assets/pics/guides/cnano/39.jpg)
+
+**For the following step, please prepare:**
+
+- 3d printed bottom housing (x1)
+- M3 screw insert (x3)
+
+{: .tip }
+There are 2 sizes of screw inserts in your kit. In this step, we will use the small ones.
+
+- Install the 3 screw inserts
+- **Use the same method as for the case**
+- Let gravity do the work
+- Push it 2/3 of the way in, then flip it and push flush against a flat surface
+
+![](../assets/pics/guides/cnano/40.jpg)
+
+## Bottom housing - screw inserts
+
+![](../assets/pics/guides/charybdis/53.jpg)
+
+**For the following step, please prepare:**
+
+- 3d printed bottom housing (x1)
+- M3 screw insert (x3)
+
+{: .tip }
+There are 2 sizes of screw inserts in your kit. In this step, we will use the small ones.
+
+{: .note }
+Depending on your kit, the bottom housing might look slightly different. The process to prepare it and install it is the same. 
+
+- Install the 2 screw inserts
+- Use the same method as for the case
+- Let gravity do the work
+- Push it 2/3 of the way in, then flip it and push flush against a flat surface
+
+![](../assets/pics/guides/charybdis/54.jpg)
+
+## Bottom housing - bearings
+
+![](../assets/pics/guides/charybdis/55.jpg)
+
+**For the following step, please prepare:**
+
+- 3d printed bottom housing (x1)
+- M3 screw (x3)
+- M3 bearing (x3)
+
+**For each of the 3 bearings:**
+
+![](../assets/pics/guides/charybdis/56.jpg)
+
+- Install the bearing in its spot
+- Screw in the M3 torx screw
+- Make sure it can rotate freely. If not, unscrew by half a turn and check again
+
+# Spin the ball
+- If you printed the case yourself, the bearings might scratch a bit against the 3d print and not roll correctly
+- Rest the trackball on top of the 3 bearings
+- Place your palm on top of the trackball
+- Applying gentle pressure, make a circle movement, make sure you can hear the bearings rotating
+- Do this for around 30 seconds, or until the trackball feels smooth
+
+# Soldering the sensor PCB to the Splinky Shield
+
+![](../assets/pics/guides/cnano/41.jpg)
+
+**For the following step, please prepare:**
+- keyboard assembly
+- sensor PCB assembly
+
+
+{: .note }
+On the pictures, we use a Splinktegrated - those come with premium kits. The Splinky + Shield work exactly the same, so inspect the pictures carefully.
+
+Inspect the Splinky shield: there is a `SPI` header, that we need to connect to the sensor PCB.
+- you can match the 3v3 with the 5V
+- the rest of the pins will aligh 
+
+![](../assets/pics/guides/cnano/42.jpg)
+
+Install the cable and solder it just like the other ones. Make sure to match the labels.
+
+![](../assets/pics/guides/cnano/43.jpg)
+
+# Placing the sensor PCB
+
+Remove the lens:
+![](../assets/pics/guides/cnano/44.jpg)
+
+Guide the sensor through the hole in the 3d print:
+
+![](../assets/pics/guides/cnano/45.jpg)
+![](../assets/pics/guides/cnano/46.jpg)
+
+Reinstall the lens:
+![](../assets/pics/guides/cnano/47.jpg)
+
+# Installing the 3d holder assembly
+
+## Top part
+
+- Insert the top sensor holder assembly into the case
+- The top sensor holder assembly has a specific way of being inserted
+- Locate the side with a cut part
+- Install it from the top of the keyboard, by pushing in the opposite side first. Use the picture below to check correct insertion
+
+![](../assets/pics/guides/charybdis/57.jpg)
+
+Push in the other side. It will scrap a little bit against the case.
+
+![](../assets/pics/guides/charybdis/58.jpg)
+
+
+## Bottom part
+
+{: .tip }
+Depending on your kit, the bottom housing might look slightly different. Install the screws to match the picture below.
+
+- Insert the bottom part of the assembly from under the case
+- Screw in the 3 screws
+- Make sure it's tight, but do not overtighten - you might damage the print
+- The whole assembly should not move at all
+
+![](../assets/pics/guides/charybdis/50.jpg)
+
+
+# Installing the sensor PCB
+
+- Install the sensor PCB on top of the holder, aligning the two holes of the PCB with the two holes of the holder
+- Screw in the sensor PCB using 2 M3 torx screws
+- Use the picture below for reference
+
+![](../assets/pics/guides/charybdis/49.jpg)
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