Closed jbuck2005 closed 1 year ago
The I2C register No.37 is to store the offset value for RTC calibration. Usually this value has been properly set in the factory, but it can be lost if firmware was updated without keeping the EEPROM values. It is possible to calibrate the RTC again by measuring the CLKOUT frequency in (unpopulated) P5 header, or count the actual time drift.
Here is an excel file that can calculate the offset value for I2C register No.37: WittyPi_RTC_Calibration.xlsx
This Excel file provides two approaches (by frequency or by time drift) to calculate the offset value. Properly setting the I2C register No.37 will make the RTC accuarate.
Is there a calibration or test routine that can be run? It appears that my RTC is losing 5s per day!!!! This is really not acceptable and I would like to look into what options exist to remedy this.
piuser@pinamehere:~ $ uptime
14:08:31 up 1 day, 4:58, 2 users, load average: 0.18, 0.17, 0.17
piuser@pinamehere:~ $ ntpq -pn
piuser@pinamehere:~ $ ./wittypi/wittyPi.sh