Submodule and protection shield.
In this course, a set of submodule PCB's will be provided for the PYNQ board. This interface connects to the physical and digital baby setups, providing easy access to power, baby sensors, and PYNQ board pins, all conveniently located next to a central breadboard. Each group will also receive a set of protection shields for their PYNQ board. This shield adds an extra layer of protection between the I/O interfaces of the PYNQ board and the breadboard interface, ensuring that a large current flow does not damage the PYNQ board.
The submodule
The image below shows the submodule. It includes the breadboard surrounded by all the terminal connectors. The plugs for these are supplied during the course. With these you can connect all interfaces to the breadboard using circuit wires. The large serial connector on the left, indicated in yellow, connects to the Baby backbone. Below there are three pairs of jumper jack connectors indicated in purple. Ensure these are connected to power the PYNQ from the baby setup. The ribbon cable indiciated in red connects your PYNQ board to all the terminal connectors on the submodule, so make sure it's plugged in.
For more information on connecting the PYNQ board to the baby, see the section Connecting the Submodule to the Baby Backbone.
Mounting the Shield
See the below image for how to mount the protection shield. First, place the protection shield on the PYNQ by aligning the gap in the shield with the Ethernet port on the PYNQ board and pushing the pins in the jumper connectors. Then, mount the LED screen to the area marked with an X .
Connect the ribbon cable, ensure uniform pressure when placing shield or LED to avoid bending the pins on the PYNQ or shield.
Protection Circuit
The protection circuit is a key part of the shield. It prevents overcurrent and voltage spikes from damaging the PYNQ board by regulating the current flow and redirecting it in case of a sudden surge.
For the Arduino pins, the circuit uses a diode to reduces reverse voltage to ground when polarity is switched. This enables these pins safely for both input and output.
The analog pins have additional protection with a buffer circuit, which only allows input to the pins. While the Switchbox application can reroute internal wiring to enable these pins to output signals without the protection shield, as indicated by A in the upper image. However with the shield on, they only accept input to protect the Analog to Digital converter. This means that the pins in location B are only input. Keep this in mind when trying to generate a PWM signal.
Removing the Shield
If you need to remove the shield, do as follows:
gently lift it from the head and back of the PYNQ board. Do not lift from the sides as it may bend the Raspberry Pi Headers and potentially disable some of them which is a common occurrance. Refer to the images below for a visual guide.
The same holds for the LED display on top of the shield. When it needs to be removed do so slowly in the same direction as the protection shield as these headers are also easily damaged.
Connecting the submodule to the baby backbone
Note that the ribbon cable needs to be connected to allow the pynqboard to be powered by the backbone.
Step 1: Set the correct jumpers on submodule
on the submodule PCB, set the provided Jumpers on S7 and S8 connectors.
Step 2: Switch the power jumper on the PYNQ
on the PYNQ, move the power jumper from the USB position to the REG position. This is to allow it te be powered from the pins instead of USB.
Step 3: Turn the Powern on the PYNQ on
On the PYNQ, turn the power switch on. This is as normal with the power toggle switch
Step 4: Connect the 12V power supply.
ONLY ON PHYSICAL BABY. On the Backbone, connect the provided 12v black power brick (NOT the LAB 3-channel universal power supply)
