As mentioned on the description and packaging, these buttons are optional and if you want to use them you will need to solder yourself. If you do, they connect as follows:
SW1 = BUT1 = pin 36 = GPIO 16
SW2 = BUT2 = pin 37 = GPIO 26
SW3 = BUT3 = pin 38 = GPIO 20
SW4 = BUT4 = pin 40 = GPIO 21
Also see the schematic area this refers to on the image here.
PaPiRus HAT has on board pull up resistors and protection resistors for the button GPIOs, so there is no need to use the internal pull-up resistors on the Raspberry Pi. You can see these on the schematic.
CN2
PaPiRus has an on board voltage regulator MCP1801T which guarantees that there is always a 3V3 rail available on the board as the screens require 3V3 power. This could be useful to power the board from different platforms which may not have 3V3 power available natively e.g. Arduino. See circuit diagram for more info.
You can configure the jumper as follows:
2-3 for 5V
1-2 for 3V3
CN14
Some of the ePaper screens have a "border control" pin which controls the status of a 1px border around the edge of the screen. The method of driving this differs between the screens and so this jumper is used to configure the border control for different screens. If you configure it incorrectly, the screen will still operate normally but will display a 1px black border around the edge of the screen (but maybe some people will want this effect?).
You can configure the jumper as follows:
2-3 for 1.44"-2.0"
1-2 for 2.7"
No for 1.9"-2.6"
CN5 3V3
CN6 5V
CN7 GND
CN8 I2C_SDA
CN9 I2C_SCL
CN10 RTC
CN11 Raspberry Pi pin 7
CN12 Raspberry Pi pin 15
On the underside of the PaPiRus HAT (picture here) you will see two FPC connectors. The one closest to the edge (with a brown clasp - CN1) is for the ePaper display to connect into. The other FPC connector (CN4), is for use as a GPIO breakout in conjunction with the GPIO breakout adapter from Watterott Electronic. This can be used in one of two ways...either to breakout the GPIO pins and use them for additional purposes whilst the HAT is on top of the Pi, or to connect the PaPiRus HAT to the Raspberry Pi from further away, using an FPC cable (for example, if you wanted to mount the screen on the side of a case but have the Pi itself in the base of the case).
There is a pogo pin included in the packaging for free. The purpose of this is to utilise the wake-on-alarm functionality built into the RTC (real time clock) on the HAT. This ties into the RUN pin on the Raspberry Pi and allows the Pi to be waken from a "halt" state at a specific time that you set in the RTC. There are two available positions for this - one for the A+/B+/2B and one for the new location on the Pi 3B. This needs to be soldered into place if you wish to use this functionality. The part number for the Pogo Pin is a Mil-Max 0908-9-15-20-75-14-11-0
The RTC is a Microchip MCP7940N and on our board it is located at 0x6F on i2c-1 when using a 40 pin Raspberry Pi. If you are using this with a 26 pin Raspberry Pi it will be on i2c-0 at the same address but this is a rare use case. The RTC has a wake-on-alarm output which is connected to the pogo pin output (listed above) and this allows you to wake up the Raspberry Pi from a halt state at a specific time and date - the pogo pin interfaces with the run header.
The temperature sensor in use is a NXP LM75BD and this is located at 0x48 on i2c-1 when using a 40 pin Raspberry Pi. If you are using this with a 26 pin Raspberry Pi it will be on i2c-0 at the same address but this is a rare use case.
Both the RTC and temperature sensor have many more features than we have documented. We will not be officially supporting all of these features as they are already well documented in the datasheets and elsewhere. But we have left them available for advanced users.
The latest hardware version of the ePaper / eInk displays themselves no longer require the PWM pin found on the PaPiRus HAT v1.9 (BCM18 / Pin 12). This is why the PaPiRus Zero hardware no longer makes use of this pin. Because of this, whilst it is connected with a trace on the PCB itself, it is not needed to be connected for the latest displays...it only remains because the PaPiRus HAT also supports some of the legacy displays from Pervasive Displays (this will likely be phased out in version 2.0).
For this reason, if you need to use BCM18 / Pin 12 for another reason, you can just cut the trace or desolder the header for that pin. Alternatively, we have had success in "disconnecting" this pin by getting a 40 pin through hole extension header and removing pin 12 out - by pulling it or cutting it out.
We are proud to say that the PaPiRus HAT is certified by the Open Source Hardware Association with UID number UK000017. Our certification mark is below:
