Because each system will consist of a transmitter and a detector, we can verify operation using a loopback circuit that is implemented on the ECEn Dev Board. Using this loopback circuit, you are essentially “shooting” yourself. The nice thing is that you can completely verify the operation of your system without connecting any external circuitry. Later on, when you connect up all the gun circuitry, if things don't work properly, you know that it is most likely that any failures that occur are caused by the newly added circuitry. This approach dramatically improves the odds of implementing a working system. A simple block diagram of the loopback circuitry with its connections is shown below. As shown the output from the transmitter pin is connected to some circuitry which, in turn, is connected to the input of the ADC. Below are pictures for both the old board (top) and the new board (below).

The schematic of the loopback circuitry is shown below. It is quite simple. It consists of a voltage divider that takes the 3.3-volt output from the transmitter pin and converts that into a voltage that is less than 1.0 volt. The ADC cannot tolerate anything over 1.0 volt so this protects the ADC circuitry. A potentiometer is provided so that you can attenuate the signal to simulate increasing gun distance. Finally a few “pull-downs” and the hit-led are connected as shown. Those 5 jumpers short the connections shown on the schematic. The names on the schematic match those on the development board. You simply use the loopback circuitry as is. The schematic is provided just for those who were curious.

The only thing you have to do is to make sure that all of the jumpers are properly installed on your development board as shown in the photo below. There should be 5 jumpers in place. If any are missing, please go to the shop and ask for shorting blocks and push them on as necessary. Alternatively, ask the TAs to help you.