The Sleepy Pi 2 exposes a mixture of Raspberry Pi GPIO and also Arduino I/O to the outside world.
The Sleepy Pi 2 is compatible with either 26-pin or 40-pin Raspberry Pi's and optionally uses the following Raspberry Pi GPIO lines:
Most of these lines are not exclusively for use with the Sleepy Pi 2 and can be used for other things if required. You can if you want reduce the GPIO count to zero if required. In the next section, I'll describe reducing the GPIO load.
If you look at each of the GPIO lines it can be seen that in certain applications, you can dispense with using them. The Sleepy Pi 2 has been designed with minimal GPIO impact in mind, but retains compatibility with Sleepy Pi 1.
As an example, you can have a Zero GPIO load. In this case, we don't use the i2c communications to talk to either the RTC or the Arduino. We don't program the Arduino or communicate with it over the serial link. Instead we program the Arduino offline via the Programming Adapter - we also disconnect GPIO 22 Reset via a solder jumper. We are not interested in the GPIO 23 Alarm, GPIO 24 or GPIO 25 Handshaking which we can disconnect with solder jumpers. We use the Current Monitor to determine when the Raspberry Pi is operating and when it is awaiting shutdown.
Between the Zero GPIO load and a Full GPIO load, you can decide which GPIO pins are required by your application and in some cases solder jumpers are available to physically disconnect the pins from the Raspberry PI GPIO connector.
The solder jumpers are as follows:
Removing solder on these jumpers will disconnect the relevant pin. The default settings for solder jumpers are shown in brackets and on the diagram and are used to maintain software compatibility with Sleepy Pi 1.
The Sleepy Pi 2 has a number of expansion connections as shown below:
You can solder directly to these pins or use a set of expansion headers and prototyping blanket to add extra soldering options.
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