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MAX31343 RTC
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MAX31343 RTC

by bludin on Tue Apr 06, 2021 5:24 pm

I'm planning to use MAX31343 RTC with a rechargeable Seiko button cell. (I might even design a breakout board if there's some interest)
    Has anybody written a lib for that yet?
    I just learned that the internal oscillator of the SAMD MCUs is very imprecise, so I thought it might be worth utilizing the (non-compensated) 32kHz CLKO output as an external oscillator. Would that make sense?
    One problem is that the CLKO output is off by default and has to be enabled by setting a register via I2C. Is it possible to switch from the internal oscillator to an external one with Circuitpython?
    Furthermore, the MAX31343 also has a compensated square wave output that can be set to 1-32Hz (not kHz). Do you have an idea how that could be put to good use?

bludin
 
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Re: MAX31343 RTC

by adafruit_support_mike on Thu Apr 08, 2021 12:04 am

We haven't used the MAX31343, but from a quick skim of the datasheet it looks roughly comparable to the DS3231. I don't know of any existing code to support it, but someone from the community might have more information.

bludin wrote:I just learned that the internal oscillator of the SAMD MCUs is very imprecise, so I thought it might be worth utilizing the (non-compensated) 32kHz CLKO output as an external oscillator. Would that make sense?

It would probably be okay. MEMS resonators are about an order of magnitude less stable than crystal oscillators, but still far better than the ~3% drift of an IC's built-in RC oscillator.

bludin wrote:One problem is that the CLKO output is off by default and has to be enabled by setting a register via I2C. Is it possible to switch from the internal oscillator to an external one with Circuitpython?

No, I don't think that feature is available.

For clock replacement, you'd get better results from a member of the Si5351A family:

https://www.adafruit.com/product/2045

They're designed to work as system clocks, and hold their configuration in memory. Set them once, and they'll start at the same frequency next time they get power.

bludin wrote:Furthermore, the MAX31343 also has a compensated square wave output that can be set to 1-32Hz (not kHz). Do you have an idea how that could be put to good use?

Only in the general 'use it to trigger periodic actions' sense.

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