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$20 add-on provides Real-Time Clock for the Raspberry Pi

Apr 27, 2021 — by Eric Brown — 540 views

On Kickstarter: a $20 “USB RTC for Raspberry Pi” Real-Time Clock add-on that plugs into a Pi’s USB port with a USB-to-UART/I2C converter to enable accurate timestamps.

A start-up led by Amrit Singh has successfully launched a Real-Time Clock add-on for the Raspberry Pi to record the passing of time and provide timestamps. The $14 USB RTC for Raspberry Pi early birds are gone, but for $20 you can receive the device in May.

The USB RTC for Raspberry Pi is not a HAT, but an add-on board/dongle that plugs into a Raspberry Pi USB port. The USB interface is said to avoid the need for jumper cables, soldering wires, or integrating an external PCB to add an RTC to the Pi.



USB RTC for Raspberry Pi with Pi (left) and spec list
(click images to enlarge)

Applications include data loggers, digital clocks, attendance systems, and timestamping for digital cameras. Despite the Raspberry Pi marketing, it appears the device can work with just about any computer with a USB port.

The device integrates a Maxim DS3231 RTC chip with a low-power temperature compensated crystal oscillator. The I2C-interface TCXO oscillator operates at 32.768kHz.



USB RTC for Raspberry Pi detail view
(click image to enlarge)

The other key component is a Microchip MCP2221 USB-to-UART/I2C serial converter, which supports 12Mbps full-speed USB transfer with 64-byte transmit and receive packets. The MCP2221 integrates a Human Interface Device (HID) for I2C for chip control and configuration. It also provides 4x GPIO pins that customers can use for analog input and output, as well as some available UART pins.

The USB RTC for Raspberry Pi, which we saw on Geeky Gadgets, is further equipped with a temperature sensor, a USB 2.0 port, and a battery holder for a 3V CR1220 coin cell. The device can be switched between 3.3V and 5V via a jumper.

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The “open source” board enables logging in 24- or 12-hour formats and offers programmable time-of-day alarms and a programmable square-wave output. The device can also automatically detect a power failure and reset to the backup coin-cell supply.

Singh previously ran a successful Kickstarter campaign for an Air Monitoring HAT. There were some delivery delays with the HAT, which is currently sold out, although on April 6, Singh posted an updated saying that all orders were finally shipped.

 
Further information

The USB RTC for Raspberry Pi is available on Kickstarter through May 2 for 14 UK Pounds ($20), which is said to be 30 percent off retail. Volume discounts are available and shipments are due in May. More information may be found on the Kickstarter page.
 

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One response to “$20 add-on provides Real-Time Clock for the Raspberry Pi”

  1. b1twise says:

    So… it’s hard to see the point of a huge USB stick when I have 5$ RTC’s for the pi that cover 5 pins and use the same chip. I’m just so negative on kickstarter campaigns because of how badly most seem to go. And all the ‘super fast usb ssd’ scams…

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