RTC not working

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Suncoaster
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RTC not working

Post by Suncoaster » Sun Jun 17, 2018 7:48 am

My RTC is no longer working, I have replaced the CR2032 battery but it makes no difference. There is 3.2v measured at the battery holder but that's it.

Any assistance would be appreciated.

Dave

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MikeB
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Re: RTC not working

Post by MikeB » Sun Jun 17, 2018 8:21 am

Check the RTC does run when you set it (I think you may have already done that).
The battery supplies power to the RTC chip (U2, a MCP79410-I/SN device) via resistor R81 (100 ohms) and diode D7, ending at pin 3 of U2. Check the battery voltage reaches each of these.

Mike
ersky9x/er9x developer
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Suncoaster
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Re: RTC not working

Post by Suncoaster » Sun Jun 17, 2018 2:16 pm

MikeB wrote:
Sun Jun 17, 2018 8:21 am
Check the RTC does run when you set it (I think you may have already done that).
The battery supplies power to the RTC chip (U2, a MCP79410-I/SN device) via resistor R81 (100 ohms) and diode D7, ending at pin 3 of U2. Check the battery voltage reaches each of these.

Mike
The RTC does not run, and the checks you have listed will require daylight to check as my eyesight under artificial light is not the best. I will check this tomorrow and report back.

Dave

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jhsa
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Re: RTC not working

Post by jhsa » Sun Jun 17, 2018 2:31 pm

Please be careful not to short anything while measuring :)

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MikeB
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Re: RTC not working

Post by MikeB » Sun Jun 17, 2018 6:18 pm

If the RTC doesn't run at all when you set it, as opposed to not keeping the time when poaered off, then the problem is unlikely to be the battery.
I'll possibly need to see if I can do some specific test firmware to help investigate.

Mike
ersky9x/er9x developer
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The impossible takes a little longer!


Suncoaster
Posts: 216
Joined: Thu Dec 29, 2011 10:18 am
Country: Australia
Location: Cooloola Cove, Australia

Re: RTC not working

Post by Suncoaster » Mon Jun 18, 2018 2:17 pm

Suncoaster wrote:
Sun Jun 17, 2018 2:16 pm
MikeB wrote:
Sun Jun 17, 2018 8:21 am
Check the RTC does run when you set it (I think you may have already done that).
The battery supplies power to the RTC chip (U2, a MCP79410-I/SN device) via resistor R81 (100 ohms) and diode D7, ending at pin 3 of U2. Check the battery voltage reaches each of these.

Mike
The RTC does not run, and the checks you have listed will require daylight to check as my eyesight under artificial light is not the best. I will check this tomorrow and report back.

Dave
I have 3.2v at pin 3 of u2.

Dave

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MikeB
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Re: RTC not working

Post by MikeB » Mon Jun 18, 2018 4:03 pm

The RTC is an I2C interface dvice, so you should see 3.3V on pins 5 and 6. Pins 1 and 2 connect to the crystal (X2).

Mike
ersky9x/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

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