Actions
Forum Thread Details
  • Replies 12 replies
  • Subscribers 190 subscribers
  • Views 2328 views
  • Users 0 members are here
Related

8 bit PIC with RTC chip.

asanyi

Hi, my circuit is composed from a PIC16F15345 microcontroller and a MCP79411 RTC chip, connected with i2c, it has an own 32.768 crystal. The 16F15345 also drives deprez meters and LEDs with PWM signals. While the power of the main circuit is switched off, the RTC runs correctly (precise timing) from its backup 3V battery. But activating the power of the PIC and the PWM driving, the RTC has lost its correct operation, delaying 30 minutes per 12 hour! Any idea to fix is accepted...

Parents

  • You need to show us the circuit diagram and ideally some pictures of the hardware.

    The kind of problem you describe is often caused by bad layout, inadequate power supply decoupling or ciruit errors.

    Without more information it is not possible to tell which, if any, is the cause here.

    MK

  • in reply to michaelkellett

    Please explain how the backup battery and the USB power interacts. Beside the hardware, the I2C commands can mess with the timer. For example, if you have code that stops the timer then restarts, it can explain loosing the 30 second you’ve mentioned.

  • in reply to ggabe

    Main power at normal operation, 5V: supplied the PIC VDD pin, supplied the MCP79411 RTC on pin8 VDD, supplied the anods of the LEDs. The deprez coil are drived from PWM pins of the PIC VIA NPN transistors, the common other ends of the coils are on the 5V of main power. RTC backup (when the main power is switched off):   simple a 3V coin battery is connected to the RTC pin3, as the manual describes. The i2c communication must not disturb the time management of the RTC. The program: the RTC alarm is programmed in sec=0 match, so once per minute. The alarm pin7 of the RTC is connected to the INT pin of the PIC, it is prorammed for falling edge interrupt. When the once per minute interrupt occurs, the interrupt rutin reads the hour and minute timekeeping register of the RTC via i2c and clear the alarm flag. I think this is the regular way. Finally here is my nice schematic...image

Reply
  • in reply to ggabe

    Main power at normal operation, 5V: supplied the PIC VDD pin, supplied the MCP79411 RTC on pin8 VDD, supplied the anods of the LEDs. The deprez coil are drived from PWM pins of the PIC VIA NPN transistors, the common other ends of the coils are on the 5V of main power. RTC backup (when the main power is switched off):   simple a 3V coin battery is connected to the RTC pin3, as the manual describes. The i2c communication must not disturb the time management of the RTC. The program: the RTC alarm is programmed in sec=0 match, so once per minute. The alarm pin7 of the RTC is connected to the INT pin of the PIC, it is prorammed for falling edge interrupt. When the once per minute interrupt occurs, the interrupt rutin reads the hour and minute timekeeping register of the RTC via i2c and clear the alarm flag. I think this is the regular way. Finally here is my nice schematic...image

Children
No Data