It also does not require external components. Internal 8.5MHz oscillator, divided by 256 (~33kHz): Provides better frequency stability than the internal 150kHz RC oscillator at the expense of higher (by 5 uA) deep sleep current consumption. In this case, the 32K_XP pin cannot be used as a GPIO pin. Additionally, a 1 nF capacitor must be placed between the 32K_XP pin and ground. Common mode voltage should be in the range of 0.1 < Vcm < 0.5xVamp, where Vamp is signal amplitude. The amplitude should be less than 1.2 V for sine wave signal and less than 1 V for square wave signal. The external clock signal must be connected to the 32K_XN pin. Provides better frequency stability at the expense of slightly higher (by 1 uA) Deep sleep current consumption.Įxternal 32kHz oscillator at 32K_XN pin: Allows using 32kHz clock generated by an external circuit. However, as frequency stability is affected by temperature fluctuations, time may drift in both Deep and Light sleep modes.Įxternal 32kHz crystal: Requires a 32kHz crystal to be connected to the 32K_XP and 32K_XN pins. Internal 150kHz RC oscillator (default): Features lowest deep sleep current consumption and no dependence on any external components. The RTC timer has the following clock sources:
If you want to choose a different timer, configure CONFIG_ESP32_TIME_SYSCALL in project configuration. It is recommended to stick to the default setting which provides maximum accuracy. The settings for the system time source are as follows: Time will be measured at 1 us resolution. It uses the APB_CLK clock source (typically 80 MHz), which has a frequency deviation of less than ☑0 ppm. The reason for using this timer is to achieve greater accuracy. High-resolution timer: Not available during any reset and sleep modes. The frequency deviation depends on an RTC Clock Source and affects accuracy only in sleep modes, in which case the time will be measured at 6.6667 us resolution. RTC timer: Allows keeping the system time during any resets and sleep modes, only the power-up reset leads to resetting the RTC timer. There are the following two time sources: The choice depends on the application purpose and accuracy requirements for system time. So a delay of 250ms comes after the print of the selected parameter and after that delay a 2 spaces is printed which makes the parameter disappears from the LCD and another 250ms delay comes after the print of the 2 spaces.System time can be kept using either one time source or two time sources simultaneously. With this function we can see the blinking of the selected parameter with a frequency of 2Hz.
When called and without pressing any button the total time is 10 x 25ms = 250ms.
Void blink_parameter() : this small function works as a delay except that it is interrupted by the buttons B1 (connected to pin 8) and B2 (connected to pin 9). Void DS3231_display() : displays time and calendar, before displaying time and calendar data are converted from BCD to decimal format. Minute = (minute > 4) * 10 + (minute & 0x0F) The DS3231 works with BCD format only and to convert the BCD to decimal and vise versa I used the 2 lines below (example for minute):
#Set up eon timer and ds clock code#
The Arduino code below doesn’t use any library for the DS3231 RTC, the Wire library is for the communication between the Arduino and the DS3231 using I2C protocol. The DS3231 Arduino code is similar to the DS1307 code and it works with both RTC chips. Button B1 selects the parameter and B2 increments the selected parameter.Īrduino real time clock with DS3231 code: In the circuit there are 2 push buttons (B1 & B2) connected to pins 8 and 9 respectively, the two push buttons are used to set time date parameters (minutes, hours, date, month and year).
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