ESP32 NodeMCU


ESP32 NodeMCU
ESP32 Docs	ESP32 Home	ESP8266 Home	Generic
Generic 2	Getting Started	Getting 3	Get Date Time
Getting Started DevBoard	ESP32 Pinout.html	Install ESP32 on IDE	Troubleshooting Guide
Config NTP Client	NodeMcu ESP32 Libs	Useful WiFi Stuff	Features
ESP32 basic	ESP32 WiFi Funcs	System Time ESP32 Pgm	Get DateTime via ESP32
ESP32 DeepSleep Wake Srcs	Get Started ESP32 Dev	ESP Time	ESP Time Zones
DS3231 Clock Instructions	DS3231 Datasheet TCX0 MAXIM	NTP Intro
ESP32 Daasheet	NodeMCU-32s Datasheet	ESP32S Datasheet Wroom	ESP32S Registers
ESP32 Datasheet	ESP32 Web Server
Interrupts
ESP32 Interrupts	Install ESP32 Board in IDE	ESP32 Interrupts	Create ESP32 Interrupts
ESP32 Interrupt Tut Configu
Events	System Events
WiFi
Conn To WiFi
Touch Sensors
Touch Sensors
Weather Station Info
Weather Station	Weather Station HTML Page	Weather Station Code


ESPRESSIF DOCS
Pgmming Guide	Espressif Site


ESP32 Internal Registers Etc.
Register Table	Address Map	I² Interface	Clock & Calendar

ESP32 Registers

Address	Bit 7 MSB	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0 LSB	Function	Range
00h	0	10 Secs			Secs				Seconds	00-59
01h	0	10 MIns			Mins				Minutes	00-59
02h	0	12,*24	*AM, PM	10 Hour	Hour				Hours	1-12 + *AM,PM 0-23
03h	0	0	0	0	0	Day O Week			Day	1-7
04h	0	0	10 Date		Date				Date	01-31
05h	Century	0	0	10 Month	Month				Month/Century	01-12 Century
06h	10 Year				Year				Year	00-99
07h	A1M1	10 Seconds			Seconds				Alarm 1 Secs	00-59
08h	A1M2	10 Minutes			Minutes				Alarm1 Mins	0-59
09h	A1M3	12, *24	*AM,PM	10 Hour	Hour				Alarm 1 Hours	1-12 + *AM,PM
09h	A1M3	12, *24	20 Hour	10 Hour	Hour				Alarm 1 Hours	0-23
0Ah	A1M4	Dy,Dt	10 Date		Day				Alarm 1 Day	1-7
0Ah	A1M4	Dy,Dt	10 Date		Date				Alarm 1 Date	1-31
0Bh	A2M2	10 Minues			Minutes				Alarm2 Minutes	0-59
0Ch	A2M3	12,*24	*AM,PM	10 Hour	Hour				Alarm 2 Hours	1-12 + *AM,PM 00-23
0Ch	A2M3	12,*24	20 Hour	10 Hour	Hour				Alarm 2 Hours	1-12 + *AM,PM 00-23
0Dh	A2M4	12 *DT	10 Date		Day				Alarm 2 Day	1-7
0Dh	A2M4	12 *DT	10 Date		Date				Alarm 2 Date	1-31
0Eh	*EOSC	BBSQW	CONV	RS2	RS1	INTCN	A2IE	A1IE	Control	-
0Fh	OSF	0	0	0	EN32kHz	BSY	A2F	A1F	Control/Status	-
10h	SIGN	DATA	DATA	DATA	DATA	DATA	DATA	DATA	Aging Offset	-
11h	SIGN	DATA	DATA	DATA	DATA	DATA	DATA	DATA	MSB of Temp	-
12h	DATA	DATA	0	0	0	0	0	0	LSB of Temp	-

Address Map

Figure 1 shows the address map for the DS3231 time- keeping registers. During a multibyte access, when the address pointer reaches the end of the register space (12h), it wraps around to location 00h. On an I 2 C START or address pointer incrementing to location 00h, the cur- rent time is transferred to a second set of registers. The time information is read from these secondary registers, while the clock may continue to run. This eliminates the need to reread the registers in case the main registers update during a read.

I 2 C Interface

The I 2 C interface is accessible whenever either V CC or V BAT is at a valid level. If a microcontroller connected www.maximintegrated.com to the DS3231 resets because of a loss of V CC or other event, it is possible that the microcontroller and DS3231 I 2 C communications could become unsynchronized, e.g., the microcontroller resets while reading data from the DS3231. When the microcontroller resets, the DS3231 I 2 C interface may be placed into a known state by tog- gling SCL until SDA is observed to be at a high level. At that point the microcontroller should pull SDA low while SCL is high, generating a START condition.

Clock and Calendar

The time and calendar information is obtained by reading the appropriate register bytes. Figure 1 illustrates the RTC registers. The time and calendar data are set or initialized by writing the appropriate register bytes. The contents of the time and calendar registers are in the binary-coded decimal (BCD) format. The DS3231 can be run in either 12-hour or 24-hour mode. Bit 6 of the hours register is defined as the 12- or 24-hour mode select bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5 is the AM/PM bit with logic-high being PM. In the 24-hour mode, bit 5 is the 20-hour bit (20–23 hours). The century bit (bit 7 of the month register) is toggled when the years register overflows from 99 to 00. The day-of-week register increments at midnight. Values that correspond to the day of week are user-defined but must be sequential (i.e., if 1 equals Sunday, then 2 equals Monday, and so on). Illogical time and date entries result in undefined operation. When reading or writing the time and date registers, sec- ondary (user) buffers are used to prevent errors when the internal registers update. When reading the time and date registers, the user buffers are synchronized to the internal registers on any START and when the register pointer rolls over to zero. The time information is read from these secondary registers, while the clock continues to run. This eliminates the need to reread the registers in case the main registers update during a read. The countdown chain is reset whenever the seconds register is written. Write transfers occur on the acknowl- edge from the DS3231. Once the countdown chain is reset, to avoid rollover issues the remaining time and date registers must be written within 1 second. The 1Hz square-wave output, if enabled, transitions high 500ms after the seconds data transfer, provided the oscillator is already running.