DFR0998 / SD3031 RTC - does it work with 3.3V?

Hi Jenna.

TL;DR

I produced this entire response and then….

Right down the bottom I provided info from the spec sheet.

And there it is staring me in the face - the I2C bus voltage is specified as 4.5 ~ 5.5 V

So, thank you very much for your offer of help, but it looks like user error → not reading the manual properly!

Though it begs the question - do you know of any other RTCs that operate at 3.3V, that will produce a periodic interrupt?

I've left my response for interest sake.

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I am using the Pico Pi W board with minimal configuration/setup.

I have pre-programmed the DFR0998 using an Arduino running at 5V.

So my Pico setup is simply reading the time from the RTC, and outputting to a serial port.

I2C pin connections:

Here's the code for my main routine - my apologies i can't find a way to attach a text file.

#include "stdio.h"#include "pico/stdlib.h"#include "pico/binary_info.h"

#include "hardware/i2c.h"

#include "MyI2CHelper.h"

#define SD3031_IIC_ADDRESS       0x32  ///< Sensor device address#define SD3031_REG_SEC           0x00  ///< RTC Seconds Register#define SD3031_REG_MIN           0x01  ///< RTC Minutes Register#define SD3031_REG_HOUR          0x02  ///< RTC Hours Register#define SD3031_REG_WEEK          0x03  ///< RTC Week Register#define SD3031_REG_DAY           0x04  ///< RTC Day Register#define SD3031_REG_MONTE         0x05  ///< RTC Month Register#define SD3031_REG_YEAR          0x06  ///< RTC Year Register#define SD3031_REG_ALARM_SEC     0x07  ///< RTC Seconds Alarm Register#define SD3031_REG_ALARM_MIN     0x08  ///< RTC Minutes Alarm Register#define SD3031_REG_ALARM_HOUR    0x09  ///< RTC Hours Alarm Register#define SD3031_REG_ALARM_WEEK    0x0A  ///< RTC Week Alarm Register#define SD3031_REG_ALARM_DAY     0x0B  ///< RTC Day Alarm Register#define SD3031_REG_ALARM_MONNTE  0x0C  ///< RTC Month Alarm Register#define SD3031_REG_ALARM_YEAR    0x0D  ///< RTC Year Alarm Register#define SD3031_REG_ALARM_CON     0x0E  ///< RTC Alarm Control Register#define SD3031_REG_CTR1          0x0F  ///< Control Register 1#define SD3031_REG_CTR2          0x10  ///< Control Register 2#define SD3031_REG_CTR3          0x11  ///< Control Register 3#define SD3031_REG_COUNTDOWM     0X13  ///< Countdown Register#define SD3031_REG_TEMP          0x16  ///< Internal Temperature Register#define SD3031_REG_IIC_CON      0x17  ///< I2C Control#define SD3031_REG_BAT_VAL       0x1A  ///< Battery Level

#define PIN_SDA 14#define PIN_SCL 15

typedef struct{ uint16_t year; uint8_t  month; uint8_t  day;//  String   week; uint8_t  hour; uint8_t minute; uint8_t second;} sTimeData_t;

uint8_t bcd2bin(uint8_t val){   return val - 6 * (val >> 4);}

int main(){   stdio_init_all();

   gpio_set_function(PIN_SDA, GPIO_FUNC_I2C);   gpio_set_function(PIN_SCL, GPIO_FUNC_I2C);

   i2c_init(i2c1, 100 * 1000);

   uint8_t data = 0;   data = 0x80;   reg_write(i2c1, SD3031_IIC_ADDRESS, SD3031_REG_IIC_CON, &data, 1);

   while (1)   {       sTimeData_t sTime;

       uint8_t buffer[7];

       reg_read(  i2c1, SD3031_IIC_ADDRESS, SD3031_REG_SEC, buffer, 7);

       sTime.year = 2000+bcd2bin(buffer[6]);       sTime.month = bcd2bin(buffer[5]);       sTime.day   = bcd2bin(buffer[4]);

       sTime.hour = bcd2bin(buffer[2]&0x7f);       sTime.minute = bcd2bin(buffer[1]);       sTime.second = bcd2bin(buffer[0]);

       printf("%d/%d/%d %d:%d:%d \r\n", sTime.year, sTime.month, sTime.day, sTime.hour, sTime.minute, sTime.second);

       sleep_ms(1000);   }} 

Here's the weird bit:

- using 3.3V from the Pico, or using a 3.7 battery - the time coming back from the RTC is garbage.

Of course, I am using common GND for all of my voltage sources, and only ever connect 1 voltage source to the VCC pin on the RTC at a time.

TBH - I believe the spec sheet is wrong, and the 2.7V specified is for the battery as opposed to a range of voltages. From original SD3031 PDF in Chinese

From PDF out of google translate:

And of course, now that I'm looking at these screen grabs - plain as day it explicitly says I2C voltage is 4.5V ~ 5.5V

Hi!

What board are you using? The operating voltage of this product is 3.3V. It should work at this voltage. Could you pls upload the code and wiring diagram? Let's find the problem better.