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Power bank keep alive device
============================
`https://bues.ch/cgit/pbwake.git/ <https://bues.ch/cgit/pbwake.git/>`_
Pbwake is a small USB stick to prevent power banks from shutting off the outputs and falling into deep sleep mode.
Pbwake uses tiny load pulses to simulate a real load on the power bank outputs. The lengths of the load pulse active (high) and inactive (low) phases are pseudo random within configurable bounds.
Pbwake is in a low power state during the inactive (low) phases. Therefore it doesn't waste too much power and guarantees high battery life of the power bank.
Tested power banks
==================
Power banks this has been tested with are:
* Anker PowerCore 20100 model A1271.
* No-name power bank 2200 mAh / 11 Wh with integrated flashlight LED.
Microcontroller
===============
Pbwake supports the following microcontrollers:
* ATTiny-13
* ATTiny-25
* ATTiny-45
* ATTiny-85
* ATMega-328P
Hardware schematics
===================
Schematics: `schematics/pbwake-attiny/pbwake.pdf <schematics/pbwake-attiny/pbwake.pdf>`_
The hardware may be built manually on a simple prototype board.
Board front side:
.. image:: doc/pbwake_front.jpg
Board back side:
.. image:: doc/pbwake_back.jpg
Prebuilt firmware images
========================
The release archives of pbwake contain prebuilt `.hex` files for all supported microcontrollers in the `hex` directory. These hex files can be flashed directly to the microcontroller with a any tool of your choice (e.g. Atmel Studio or avrdude).
The corresponding fuse settings can be found in the file `fuses.txt` in the same directory.
Building the firmware
=====================
The firmware build needs the following tool chain:
* Unix-like operating system
* GNU make
* AVR GCC
* AVR Binutils
* avrdude
Run the following commands to build the firmware:
.. code:: sh
cd firmware
make DEV=t85
Please specify the target microcontroller using the DEV variable as shown above.
Valid values are:
=============== ===========
Microcontroller make option
=============== ===========
ATTiny 13 `DEV=t13`
ATTiny 25 `DEV=t25`
ATTiny 45 `DEV=t45`
ATTiny 85 `DEV=t85`
ATMega 328P `DEV=m328p`
=============== ===========
Additional build options that can be passed to `make`:
================ ======= ================================================================
make option default description
================ ======= ================================================================
CONF_HIGH_MIN_MS 4 Minimum length of high-phase (in milliseconds).
CONF_HIGH_MAX_MS 6 Maximum length of high-phase (in milliseconds).
CONF_LOW_MIN_MS 40000 Minimum length of low-phase (in milliseconds).
CONF_LOW_MAX_MS 55000 Maximum length of low-phase (in milliseconds).
================ ======= ================================================================
Flashing the firmware after build
=================================
Run the following commands to flash the firmware to the target microcontroller:
.. code:: sh
cd firmware
make DEV=t85 print_fuses
make DEV=t85 write_fuses
make DEV=t85 write_mem
Or alternatively use any other of the available AVR flashing tools to program the .hex file and fuses.
License
=======
Copyright (c) 2020 Michael Buesch <m@bues.ch>
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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