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Sleepy Pi
Introduction
The Sleepy Pi is essentially a Smart Power Management board for the Raspberry Pi that
includes a low power Arduino that stays powered when the Raspberry Pi is off. In this way it
can reduce the overall power used by the RPi, particularly when powered from batteries in
applications where the RPi doesn’t need to be on all the time. You can think of it as adding a
“Sleep” mode to the Raspberry Pi, because the Arduino can periodically wake the RPi up to
perform a task and then put it back to sleep. As a side benefit you also get some Arduino I/O
to play with, like Analogue Inputs and PWM’s.
Key benefits include:
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Reduce the effective Power consumption of the Raspberry Pi
Power directly from batteries up to 17V
Adds Arduino I/O to the Raspberry Pi such as Analogue In or PWM
Break out the Raspberry Pi GPIO & Arduino I/O to screw terminals
Prototyping area and expansion headers for daughter boards
Power button for manual switch on/off
“Wake” or “Sleep” in response to events or triggers such as:
o Analogue value crosses a threshold
o Digital input changes
o Specific time to “wake” via Real-time Clock
Sleepy Pi
Information & code examples
All Sleepy Pi Info!
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Sleepy Pi FAQ
Installation and Powering
Setting up the Arduino IDE on Raspbian
Programming from the Arduino IDE
Writing Arduino Code on the Sleepy Pi
Getting the Sleepy Pi to Shutdown the Raspberry Pi
Programming the Sleepy Pi as a Standalone Board
Accessing the Real-Time Clock from the Raspberry Pi
Here: http://spellfoundry.com/sleepy-pi/
Sleepy Pi examples and libraries here: https://github.com/SpellFoundry/SleepyPi
Setting up the Arduino IDE on Raspbian
(It should be possible to apply these same steps for ARCH Linux)
The Arduino processor on the Sleepy Pi can be programmed directly from the Arduino IDE
running on the Raspberry Pi.
Step 1: Arduino IDE Installation
The first step is to load the Arduino environment onto the Raspberry Pi. It is a good idea to
ensure that your OS is up to date by executing the following lines (we are going to need
internet access to our RPi):
sudo apt-get update
sudo apt-get update –fix-missing
sudo apt-get dist-upgrade
This last command could need several minutes. It will ensure that we have the latest
versions of RPi.GPIO which will be required later.
Now install the Arduino IDE:
sudo apt-get install arduino
Sleepy Pi
Step 2: Disable Serial login
The Arduino processor on the SPi can be programmed directly from the RPi using the serial
GPIO lines on the RPi and another GPIO line to reset the Arduino to allow automatic code
upload. These pins are:
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GPIO 14: TXD
GPIO 15: RXD
GPIO 22: Reset (see next section)
By default RPi has exclusive access to the serial pins to output status, debug data and logging
in. Raspbian allows us to login using the serial port. To use the Sleepy Pi we need to disable
this, so we need to edit the following document:
sudo leafpad /etc/inittab
We need to comment the last line out with “#” and save it.
#Spawn a getty on Raspberry Pi Serial line
#T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100
Step 3: Disable Boot info
When Raspbian boots up it outputs boot information to the serial port and hence streams in
to the SPi (which is not particularly intersested in it). To disable this we need to edit this
document:
sudo leafpad /boot/cmdline.txt
We need to delete the following part in bold style:
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200
console=tty1 root=/dev/mmcblk0p6 rootfstype=ext4 elevator=deadline
rootwait
Step 4: Link the Serial port to the Arduino IDE
The Arduino EDE wants to use the /dev/ttyS0 serial port, but we need to use the
/dev/ttyAMA0 which is linked to the GPIO. In order to do this, we need to create a
permanent link that maps AMA0 to S0, so we need to create a small file:
sudo leafpad
We type the following lines in the new file and save it called “80-sleepypi.rules” to
/etc/udev/rules.d/ :
KERNEL=="ttyAMA0", SYMLINK+="ttyS0",GROUP="dialout",MODE:=0666
KERNEL=="ttyACM0", SYMLINK+="ttyS1",GROUP="dialout",MODE:=0666
Sleepy Pi
Step 5: Setting up the Reset (DTR) pin
The Sleepy Pi Arduino processor reset line in connected to GPIO 22. To automatically upload
code from the Arduino IDE we need to pulse this line low to rest the Arduino and enter
bootload mode.
On a normal Arduino system connected to a computer via a USB / serial cable the reset line
is connected to the DTR line. To replicate this behavior on the Raspberry Pi we need to hack
the AVRDude programming software. Dean Mao has detailed a great hack for this. He’s
produced a modified version of Avrdude (avrdude-autoreset) and written a piece of python
code (autoreset) that runs in the background and pulses the GPIO line when required.
Download code as a ZIP file https://github.com/SpellFoundry/avrdude-rpi
After unzip the file, we use the following commands:
cd ./avrdude-rpi-master/
sudo cp autoreset /usr/bin
sudo cp avrdude-autoreset /usr/bin
sudo mv /usr/bin/avrdude /usr/bin/avrdude-original
This renames our original avrdude, so we have a backup and replace it with the new one.
sudo ln –s /usr/bin/avrdude-autoreset /usr/bin/avrdude
Link the new avrdude-autoreset to avrdude so that when something calls for it, the new
version runs instead.
Step 6: Adding the SPi to the Arduino environment
To enable the Sleepy Pi to be selected from the IDE you need to add a folder and file to your
sketchbook. If it is a fresh install and you haven’t yet run the Arduino environment you’ll
need to create a sketchbook folder (skip this step if it already exists).
mkdir /home/pi/sketchbook
mkdir /home/pi/sketchbook/hardware
mkdir /home/pi/sketchbook/hardware/Sleepy_pi
Sleepy Pi
Now we have to create a new file boards.txt with the configuration RPi will need:
sleepypi.name=Sleepy Pi
sleepypi.upload.protocol=arduino
sleepypi.upload.maximum_size=30720
sleepypi.upload.speed=57600
sleepypi.bootloader.low_fuses=0xFF
sleepypi.bootloader.high_fuses=0xDA
sleepypi.bootloader.extended_fuses=0x05
sleepypi.bootloader.path=arduino:atmega
sleepypi.bootloader.file=ATmegaBOOT_168_atmega328_pro_8MHz.hex
sleepypi.bootloader.unlock_bits=0x3F
sleepypi.bootloader.lock_bits=0x0F
sleepypi.build.mcu=atmega328p
sleepypi.build.f_cpu=8000000L
sleepypi.build.core=arduino:arduino
sleepypi.build.variant=arduino:standard
Step 7: Reboot the RPi
sudo reboot
Programming from the Arduino IDE
The Arduino IDE can be found on the Main GUI menu in the Electronics section.
Sleepy Pi
Once loaded the Sleepy Pi should be selected as a target from the Tools menu.
Press the “Upload” button and the sketch will be compiled and uploaded.