MCP79520 RTC over SPI with Bascom

EDC · Joined: 26 Mar 2014 Posts: 971

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.

albertsm · Joined: 09 Apr 2004 Posts: 5915 Location: Holland

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.

EDC · Joined: 26 Mar 2014 Posts: 971

Okay. :::::: Very Happy

I need it and must use it ...and with bascom it was easy Very Happy

Duval JP · Joined: 22 Jun 2004 Posts: 1161 Location: France

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

EDC · Joined: 26 Mar 2014 Posts: 971

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...

EDC · Joined: 26 Mar 2014 Posts: 971

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:

albertsm · Joined: 09 Apr 2004 Posts: 5915 Location: Holland

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

EDC · Joined: 26 Mar 2014 Posts: 971

Since only this year February had 29 days and we have a leap year another small error came out.
The RTC itself recognizes such a year and sets bit 5 in the month register.
Therefore, it should be masked when reading it.