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USB Sensor Reader Hardware

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We shall break down the entire PCB into smaller sections and explain each one as shown on the image below. There aren't many parts on this Gizmo, however it is best to read through this to understand better how the device functions and what parts it consists of.
 
Input & Output Signals (I/O)

As you can see from the image above, there are 4 inputs located on each of the 4 headers. Although there are 4 inputs, 2 of them can be considered as 1 (i2C) since an SDA and SCL signals are needed to be able to retrieve data for this protocol. The Other 2 signals are for 1 Wire interface and Digital/Analog. You cannot read both type of signals from the same port at the same time.

Sensor Reader IC


There are 4 IC's for each set of signals. These are PIC16F88 and are operating on 10MHz. The best way to describe how these IC's are connected is to show the schematics for it. So below are the connections as they are on the PCB.

 
Main MCU (Micro Controller Unit)
 


All 4 PIC16F88 are connected to a central unit through a Serial Interface. The central unit is a PIC16F877A and is operating at 20MHz. All the processing, configurations and output is done from this unit. As a final step all the data is outputted from the Serial port of the MCU and converted to a USB signal for a PC interface and readout. Below is the Schematic of these connections for a better understanding on how all this is connected.



Misc Ports


There are some "Extra" ports on the PCB. These are the ICSP ports for each MCU for re flashing of the firmware and updates.

You can find all the Schematics for this Gizmo (with a PDF version of it) in our Projects section. Also any documentation of the hardware for this Gizmo can also be found there.

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