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MCP79520 RTC over SPI with Bascom

 
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EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 757

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PostPosted: Thu Oct 22, 2020 4:27 pm    Post subject: MCP79520 RTC over SPI with Bascom Reply with quote

Hello.
This is the basic example of handling this RTC with the Bascom syntax like $Tme & $Date
It work over SPI not I2C.



Chip have 64Bytes of battery keeped/powered RAM and some Eeprom.
It can tell when power was down and when it rise up again.
Ofcourse two alarms are also available.
Can be digitaly calibrated by one register.
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albertsm

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Joined: 09 Apr 2004
Posts: 5316
Location: Holland

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PostPosted: Fri Oct 23, 2020 12:08 pm    Post subject: Reply with quote

Excellent work EDC.
Thanks for sharing your work.
I see the attachment is complete with PDF and code.

If you dont mind i add it to the bascom samples.

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EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 757

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PostPosted: Fri Oct 23, 2020 10:36 pm    Post subject: Reply with quote

Okay. ::::::Very Happy
I need it and must use it ...and with bascom it was easy Very Happy
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Duval JP

Bascom Member



Joined: 22 Jun 2004
Posts: 1019
Location: France

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PostPosted: Sat Oct 24, 2020 10:09 am    Post subject: Reply with quote

Hi EDC
I use DS3231 with internal cristal. It is a TCXO (very higt precision ) and I2C connexion (2 wires and it lets SPI for AVRdos or others) Why did you prefer yours ?
I'm only curious
JP
Wink

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EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 757

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PostPosted: Sun Oct 25, 2020 7:28 am    Post subject: Reply with quote

Cause my AVR device is also I2C slave. In this project Im also using AVR-DOS and W5500 Ethernet chip so..for SPI it is not a problem...
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EDC

Bascom Expert



Joined: 26 Mar 2014
Posts: 757

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PostPosted: Wed Nov 24, 2021 8:51 pm    Post subject: Reply with quote

For reasons beyond my control, I had to postpone the project using this RTC.
Now Im working wit it again and one very interesting issue came out.
This RTC dont work on battery hahahahaha Very Happy

Third bit of DayOfWeek byte must be set to join battery with RTC. This bit is disabled by default.
This is handy in some cases I think. You can install battery in your commercial device and ship it no worries about the battery.
Only when end user set the clock then battery will be joined with the clock.

This is made by this line -> "Rtc_buff(6) = Makebcd(day_of_week) Or &B0000_1000" so DayOfWeek must be send atleast once.

Corrected code below:
Code:
Settime:

  Rtc_buff(1) = Write_
  Rtc_buff(2) = &H01                                        'point to seconds
  Rtc_buff(3) = Makebcd(_sec) Or &B1000_0000                'bit 7 starts oscillator
  Rtc_buff(4) = Makebcd(_min)
  Rtc_buff(5) = Makebcd(_hour)
  Rtc_buff(6) = Makebcd(day_of_week) Or &B0000_1000         'bit 3 enables battery backup
  Reset Rtc_ss
   Spiout Rtc_buff(1) , 6
  Set Rtc_ss

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albertsm

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Joined: 09 Apr 2004
Posts: 5316
Location: Holland

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PostPosted: Thu Nov 25, 2021 10:56 am    Post subject: Reply with quote

thanks for the update. indeed this is valuable info Very Happy
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