rroels/PCF2131-breakout2Small breakout board for the NXP PCF2131 RTC
PCF2131-breakout is an open-source printed circuit board by rroels, from the rroels/PCF2131-breakout repository on GitHub. It is a 2-layer board of 34.2 × 19 mm with 9 parts on 12 nets, routed with 144 tracks and 16 vias.
It is built around the PCF2131TFY. Its parts include 4 resistors, 2 capacitors, 2 connectors and 1 IC. It belongs with the interfaces and adapters and microcontroller boards boards of this library.
[!WARNING] The information and material (code, designs, files, ...) are provided "AS IS". We make no representation or warranty of any kind, express or implied, regarding the accuracy, adequacy, validity, reliability, availability, or completeness of any information or material. Use this at your own risk.
This repository contains a small breakout board for the NXP PCF2131 RTC.
The board has already been manufactured and tested, and I can confirm it works.
However, some design choices have been made that might not meet your needs. For instance, the board is wired for I2C communication only, and there is no support for battery switch-over. Please read section "Design Considerations" for more info on the design choices.
For use with an Arduino, the RTC NXP Arduino library can be used to interface with the chip.
We base ourselves on the following recommended circuits from the datasheet:
I deliberately left out the RC filter for battery switch-over functionality, which led to the following schematics:
| Reference | Footprint | Qty | Value |
|---|---|---|---|
| C1 | C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | 1 | 1nF |
| R3,R4 | R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | 2 | 10k |
| J1 | PinHeader_2x02_P2.54mm_Vertical | 1 | Conn_01x04 |
| R2,R1 | R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | 2 | 4.7k |
| C2 | C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | 1 | 100nF |
| IC1 | SON50P350X450X150-17N-D | 1 | PCF2131TFY |
| J2 | PinHeader_1x07_P2.54mm_Horizontal | 1 | Conn_01x07 |
See image of the PCB below to have a better idea of what these components look like.
All capacitors and resistors and SMD 0603. Instead of the horizontal pin header I used, a vertical pin header will also work fine (as long as the pitch is 2.54mm).
The Gerber file is in this repository (gerber/PCF2131-breakout.zip). Simply upload this file a PCB manufacturer of your choice (JLPCB, PCBWay, ...), and you they will make it for you for as low as $5 for 5 pieces (with the cheapest shipping option, which can take a few weeks).
[!WARNING] Note that you will still have to solder the components onto the PCB yourself!
Everything you need to edit this design in KiCad 8 is included in the repository.
However, this project uses symbols, footprints and 3D models from Component Search Engine. Their license allows us to do pretty much whatever we want with them, except redistributing them. For this reason I can't include them in this repository.
If you would like to edit the design yourself, you will need to download the following component libraries from https://componentsearchengine.com/ (it's free!):
From the downloaded zip file, move the content of the KiCad and 3D subfolders into the project structure, so that the end-result looks like this:
The KiCad project is configured to look for these files in these locations, using relative paths, so no changes to the project itself are required.
| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 10k | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R3, R4 |
| 2 | 4.7k | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R1, R2 |
| 1 | 100nF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C2 |
| 1 | 1nF | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C1 |
| 1 | Conn_01x04 | Connector_PinHeader_2.54mm:PinHeader_2x02_P2.54mm_Vertical | J1 |
| 1 | Conn_01x07 | Connector_PinHeader_2.54mm:PinHeader_1x07_P2.54mm_Horizontal | J2 |
| 1 | PCF2131TFY | PCF2131TFY:SON50P350X450X150-17N-D | IC1 |
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It measures 34.2 × 19 mm and has 2 copper layers, 1.6 mm thick.
9 parts, built around the PCF2131TFY. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
From the rroels/PCF2131-breakout repository on GitHub, at the commit this page was made from: the board is PCF2131-breakout.kicad_pcb and its schematic PCF2131-breakout.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Its repository states no licence, so its author keeps all rights: ask rroels before reusing the design.
