Techno Innov Pi RTC and NVMEM Extention System

Product Specifications

• Product Name: PiRTC_SRM Board v0.2
• RTC: Real-Time Clock with Super-Capa power backup
• Non-volatile RAM: 64 bytes
• Connector: 26 pins, compatible with common extension connectors on SBCs
• Designed for: Embedded ARM development using open source software

Product Usage Instructions

Hardware Overview:
The PiRTC_SRM Board v0.2 is an electronics development and prototyping adapter board designed for Single Board Computers (SBC) like OrangePi or Raspberry Pi SBCs. It features an RTC with Super-Capa power backup and 64 bytes of non-volatile RAM.

Hardware Setup:
Connect the PiRTC_SRM board to the SBC using the 26-pin connector, ensuring proper alignment.

Software Configuration:
Configure your SBC to recognize and utilize the RTC and NVMEM features provided by the PiRTC_SRM board.

Development Environment:
If you wish to modify the design or source files of the PiRTC_SRM board, you can use KiCad EDA (GPL) for editing and customization.

Introduction

• You are reading the System Reference Manual for the Pi RTC.
• The Pi RTC is an electronics development and prototyping adapter board for Single Board Computers (SBC) like OrangePi or Raspberry PI SBC’s.
• The Pi RTC provides an RTC with Super-Capa power backup and 64 bytes of non-volatile RAM.
• The Board uses the 26 pins version of the common extention connector found on many SBC with a form factor close to the original Raspberry Pi, often compatible with the pinout of the 40 pin connector.
• The Pi RTC is designed for users interested in embedded ARM development using free, libre and open source softwares only.
• Every information about the design is available and all components documentations are freely accessible. You can download the source files for the Pi RTC and modify them using KiCad 1 EDA (GPL) according to the license terms found in the license section.
• You can create and produce your own Pi RTC or a modified version (but not sell them).

Licenses

Documentation license

• The present document is under Creative Commons CC BY-SA-NC 4.0 2 License.
• It is written in LATEX and the PDF version is generated using pdflatex.

Hardware license

• The Pi RTC hardware and schematics are under Creative Commons CC BY-SA-NC 4.0 3 License.
• You can produce your own original or modified version of the Pi RTC, and use it however you like, but not sell them, even without profit.

Software license
All the software examples created for the Pi RTC are under GPLv3 License.

Hardware

Dimensions
Figure 1 gives the different dimensions and the positions of the main elements of the Pi RTC.

Connectors

P1 Connector
P1 connector is a standard 2.54mm (0.1 inch) pitch header, with 2 row of 13 pins. P1 connector provides access to the common PI expansion header.

Electronics

• The Pi RTC has been created using KiCad 4 EDA software suite for the creation of the schematics and printed circuit boards.
• See page 9 in the annexes for the full schematics. The sources for the schematics are available for download from the tindie product page and the Pi RTC directory 5 on techdata.techno-innov.fr.

  

  Name	Description
  U1	NXP PCF85363 RTC Clock.
  U2	TI LP2985 DC-DC step-down converter.
  SC1	Bussmann 1 Farad supercapacitor.

I2C

The Pi RTC uses the only I2C bus from the 26 pins Pi connector. Bus 1 holds the PCF85363 RTC clock at address 0x51.

I2C Addresses
Table 3 shows all the possible I2C Addresses for the components used on the PiRTC.

RTC Clock

• The Pi RTC includes a PCF85363 RTC with super-capacitor power backup.
• The use of a Super-capacitor for power backup lowers the environmental footprint and remove the need to replace (and dispose of) the battery at the expense of a shorter time retention, which is between one and two months, but should be enough for most applications.
• The Linux kernel has support for the PCF85363 RTC in the rtc-pcf85363 module (CONFIG_RTC_DRV_PCF85363). After loading the rtc-pcf85363 module in the kernel, you must add the RTC to the list of devices on the I2C bus 1 : echo pcf85363 0x51 > /sys/bus/i2c/devices/i2c-1/new_device
• This is not necessary if the device tree already contains the corresponding information.
• You can the access the RTC with the hwclock command (from the util-linux package on Debian based GNU/Linux distributions) as one of the /dev/rtcN (replace ’N’ with the appropriate RTC number).

NVMEM

• The PCF85363 RTC includes 64 bytes of non-volatile RAM (so long as the supercapacitor power runs).
• In order to be able to access this memory you must have the following config set in your Linux Kernel.
  • CONFIG_RTC_NVMEM=y
  • CONFIG_NVMEM=y
  • CONFIG_NVMEM_SYSFS=y
• Refer to our Wiki for further information about how to use the NVMEM.

Software

• We noticed that software information evolves way too quickly to be included in such a documentation.
• You will find all relevant information on our public wiki : http://wiki.techno-innov.fr/index.php/Products/PiRTC

Board revisions history

v0.1

• This board revision has not been sold to public.
• First prototype version, produced on customer request.

v0.2

• Actual version sold as of writting of this documentation.
• Move RTC GPIO Pin to P1 pin7 instead of P1 pin 8 (UART Tx).

Annexes

Schematics
The board schematics and PCB layout have been created using KiCad 7 EDA software suite. You can download the sources on the PiRTC page 8 on wiki.techno-innov.fr.

BOM

Note: Components used on Board may change for functionnally equivalent references without prior notice

Document revision History

Disclaimer
The Pi RTC is provided “as is” without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the Pi RTC is with you. Should the Pi RTC prove defective, you assume the cost of all necessary servicing, repair or correction.

Frequently Asked Questions (FAQ)

• Can I sell my own version of the PiRTC_SRM board?
  According to the license terms, you are allowed to create and produce modified versions of the PiRTC_SRM board for personal use, but not for commercial sale.
• Is the PiRTC_SRM board compatible with all SBCs?
  The PiRTC_SRM board is designed to be compatible with Single Board Computers that feature a similar form factor and pinout to the Raspberry Pi.

Documents / Resources

Techno Innov Pi RTC and NVMEM Extention System [pdf] User Manual Board v0.2, Pi RTC and NVMEM Extention System, Pi RTC and, NVMEM Extention System, Extention System, System

References

• User Manual