RTC board

[Sorgelig]

New board for MiSTer - RTC
It's optional. For those who want their MISTer have the real time any time.

There will be be Linux and some cores update to utilize this board.

[Newsdee]

I knew it I guessed from some of your renders.

[Sorgelig]

yeah, it wasn't a secret.
It's strange that DE10-nano includes useless I2C accelerometer chip which is like 5th leg for dog. How they supposed to use accelerometer on board full of connected wires - it's pretty stationary device. They should include RTC instead which is pretty natural chip for such board.

[TorsteinP]

It's strange that DE10-nano includes useless I2C accelerometer chip which is like 5th leg for dog. How they supposed to use accelerometer on board full of connected wires - it's pretty stationary device. They should include RTC instead which is pretty natural chip for such board.

Since DE10-nano is so small, it can be used in drones and robots. Accelerometer makes more sence then

[Sorgelig]

Since DE10-nano is so small, it can be used in drones and robots. Accelerometer makes more sence then

especially if you check the power consumption and heat dissipation

[Newsdee]

Maybe it was just a matter of space utilization on the board / cost reduction? The RPi doesn't have an RTC either.
The DE10 is small enough for mobile devices, maybe the accelerometer could be used as controller?

[TorsteinP]

Question. Why are there 18 pins on the board connector when there are only 14 pins on DE10-nano? It looks like there are space on both sides so it probably doesn't matter. I'm just wondering..

[Sorgelig]

Question. Why are there 18 pins on the board connector when there are only 14 pins on DE10-nano? It looks like there are space on both sides so it probably doesn't matter. I'm just wondering..

It's a good question!
I've found that if i would use 14 pin connector then it's easy to shift the connector while connecting RTC board to the main board due to large space on both sides inside the boxed connector. That's why i've decided to use 18pin connector which perfectly fits inside and doesn't allow shifting.
But you may use 14pin connector if you cannot find 18pin. Then be careful when you connect the board - it's pretty hard to see the alignment.

[THaase]

Hi Sorgelig,

I'm finding your MiSTer Project very interesting and will try to go for it in the near future.

As the Option boards are (more or less) needed I've alreay ordered 10pcs of each board by PCBWay.
While they are on shipment I'm trying to already get the needed parts.

As the SDRAM Board is clear, I've started with the RTC Board.

Can you confirm that the following parts should fit for the RTC Board?

X1 https://www.digikey.com/products/en?key ... 37-1-ND%20
B1 https://www.digikey.com/products/en?key ... 6-CT-ND%20
U1 https://www.digikey.com/products/en?key ... 2FMS-ND%20
R1,R2 https://www.digikey.com/products/en?key ... CRCT-ND%20
C1 https://www.digikey.com/products/en?key ... 25-1-ND%20
P1 https://www.aliexpress.com/item/10-pcs- ... a0a86f5ef1

Thanks a lot in advance.

[Sorgelig]

I cannot confirm first two parts as they are not the same i've used. Battery holder has other positions of legs so i don't know if it will fit. Same goes for XTal.

[THaase]

Thanks a lot - may I know which components you've used?

[Sorgelig]

Thanks a lot - may I know which components you've used?

i wrote the part numbers in schematics. See the PDF file.

[THaase]

Stupid me -I'll check.

Thanks

[TorsteinP]

How do I adjust DST? My minimigs clock is 2 hours late

[Sorgelig]

How do I adjust DST? My minimigs clock is 2 hours late

https://github.com/MiSTer-devel/Main_Mi ... /RTC-board

[TorsteinP]

How do I adjust DST? My minimigs clock is 2 hours late

https://github.com/MiSTer-devel/Main_Mi ... /RTC-board

Ahh! Thanks

[TorsteinP]

Are time and date supposed to be saved when powered off and be restored when powered on without internet connection?
If so, it isn't working. Made 2 boards so far and none of them saves the time.

When network cable is plugged in and I turn on power, date and time shows up in menu after a few seconds. I've left it running for 30+ minutes then turned it off, unplugged network cable, turned it on and date time never shows unless network cable is plugged in.

I'm using the M41T81 chip and a 12.5 pF x-tal. And I've checked that the battery is ok.

[Sorgelig]

Of course saving the date/time during power off is the main task of RTC board.

make sure you've updated the linux part (use SD installer tool) to latest one. Older versions don't support RTC board.
Date/time is not immediately saved to RTC board. Linux saves it once per 11 minutes.
So, you need to keep MiSTer working around 15minutes at least, and with internet connected to the board.

There is a manual setting the date and saving to rtc using linux console, but it's out of this discussion. You may find the linux info on internet if you want to do some manual work.

[kolla]

hwclock --systohc

:p

[TorsteinP]

hwclock --systohc

:p

Thanks, that did it!
Just had to add -u since my local time is +2 ahead of UTC.

[Sorgelig]

The short version it is:
store datetime to RTC:

Code: Select all

hwclock -wu

read RTC:

Code: Select all

hwclock -u

Thanks, that did it!

so, did you fix your problem with RTC?

[Sorgelig]

i found problem with M41T81S chip. After some time in power off it starts to show wrong date - several days behind the actual date.
I don't know if there is problem with particular chip or any M41T81S will work this way.
I have two other boards with M41T81 and MCP79410 - both keep time reliably.

The difference between M41T81 and M41T81S is very minor - the second one has flag of low battery voltage.

[TorsteinP]

i found problem with M41T81S chip. After some time in power off it starts to show wrong date - several days behind the actual date.
I don't know if there is problem with particular chip or any M41T81S will work this way.
I have two other boards with M41T81 and MCP79410 - both keep time reliably.

The difference between M41T81 and M41T81S is very minor - the second one has flag of low battery voltage.

When I tried again today after the MiSTer had been powered off for 18 hours, the date and time was same as when I powered it off yesterday.
This tells me that the crystal isn't working. I used SER4080CT-ND from digikey.

Lucky for me I have some old fashion crystals (they looks like a tiny pencil with legs) previously used with another RTC chip. There's plenty of room for it on RTC and this time it's working. Powered off for 5 mins after setting the time and when I powered on, time had advance correct amount of time.

[Sorgelig]

I'm glad you've fixed the problem.
Crystals are tricky. Besides the frequency they need to have appropriate load capacity. Some RTC chips require 6-9pF while others require 12pF. So, i've tried to make universal pads for different crystal sizes, and even for crystals with wired pins like you're using now.

[TorsteinP]

DigiKey part numbers for crystal CMR200T I found working is 300-8340-6-ND and I use the RTC chip M41T81 with number 497-4709-1-ND.