https://github.com/adoconnection/raspi-supercap

Raspberry Pi supercapacitor UPS shield
https://github.com/adoconnection/raspi-supercap

Last synced: about 1 month ago
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Raspberry Pi supercapacitor UPS shield

• Host: GitHub
• URL: https://github.com/adoconnection/raspi-supercap
• Owner: adoconnection
• Created: 2018-12-19T18:58:36.000Z (about 6 years ago)
• Default Branch: master
• Last Pushed: 2021-04-17T17:34:07.000Z (over 3 years ago)
• Last Synced: 2024-08-02T05:06:50.018Z (5 months ago)
• Language: C++
• Size: 275 KB
• Stars: 12
• Watchers: 2
• Forks: 2
• Open Issues: 2
• Metadata Files:
  • Readme: README.md

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README

        
# raspi-supercap

Open source Raspberry Pi supercapacitor UPS hat

## Goal 

Make reliable turn on / shutdown shield for Raspberry Pi

## Status

PoC assembly

(!) Not yet tested ;)

![v1](https://github.com/adoconnection/raspi-supercap/blob/master/PCBv1.0.PNG)

![v1](https://github.com/adoconnection/raspi-supercap/blob/master/PCB-B.1.PNG)

## BOM

* PCB – https://easyeda.com/adoconnection/raspi-supercap

* 20F x 2 supercapacitors

* ATMega328

* resistors

* diodes

* MT3608 DC-DC Step up converter board

## Open questions

- [x] Use special supercapacitor chargers or not? (https://www.analog.com/en/ltc3225) – not in v1

## To-Do checklist 

- [x] Firmware

- [x] Monitor PI state

- [x] Call shutdown pin

- [x] On power on wait for capacitors to be charged and turn on Raspberry

- [x] I2C slave to query external power status and capacitors charge level

- [x] Reset Raspberry pi if shutdown was activated and power is restored

- [ ] Customizable power off behavior

![v1](https://github.com/adoconnection/raspi-supercap/blob/master/Workflow.png)

## I2C 

Default bus address is 0x77

Registers:

| Address  | Mode | Default value | Info |

| ------------- | ------------- | ------------- | ------------- |

| 0x01  | R  | 0x64 | Test register, always return 0x64  |

| 0x02  | R  |  | External power connected. Return 0x00 or 0x01  |

| 0x03  | R  |  | Capacitor charge in percents 0 - 100  |

| 0x04  | RW  | 3 | Turn off timeout in seconds. Wait for N seconds before issue a turn off command.  |

| 0x05  | RW  | 50 | Turn off threshold. Shutdown pi at 50% charge left. |

| 0x06  | RW  | 30 | Turn on threshold. Pi boot at 40% charged capacitors. Valid values 0 - 100  |

| 0x50  | RW  | 0x21 | I2C address |

## Sources of inspiration

* https://juice4halt.com/

* https://www.saveyourpi.com/

* https://www.youtube.com/watch?v=m20o3P-S5s8

* http://www.hackerspace-ffm.de/wiki/index.php?title=Raspi_EDLC_UPS

* https://raspberrypi.stackexchange.com/questions/74641/how-to-make-a-simple-reliable-15-second-ups-for-shutdown

* https://raspberrypi.stackexchange.com/questions/22579/pi-headless-how-to-confirm-that-the-pi-is-shut-down

* https://raspberrypi.stackexchange.com/questions/5489/how-do-i-turn-on-my-raspberry-pi-after-shutdown

* https://code.google.com/archive/p/tinkerit/wikis/SecretVoltmeter.wiki

* https://www.arduino.cc/en/Tutorial/MasterWriter

* https://raspberrypi.stackexchange.com/questions/3704/i2c-library-for-mono-c