Reading DS3231 RTC in Node Red

Dashboard
1

Is there a simple way to input time to display on the dashboard from the DS3231 RTC module? Using the I2C IN node, I can see and read what looks like seconds and minutes data using the 00 and 01 commands in those nodes. The SECONDS update to a new number every second, but it isn't decimal. The seconds start at 0 and count to 9 then jump to 16. It displays erratically up to 100 and then the minutes digit changes.

So now I suppose I have to decode this somehow to decimal to display a real looking clock on the dashboard.

This seem very awkward. Is there a simpler way?

2

I think that is called binary coded decimal. Been ages since I’ve seen it but I’m sure google will help

3

Looking at the datasheet the upper 4 bits are the 10 seconds and the lower the seconds, same for the minutes etc.
I don't know Javascript good enough for bit manipulation.
In C we AND the right 4 bits to get the seconds value and then shift the left 4 bits to right to get 10th seconds value.

rtc
rtc870×263 15.1 KB

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4

Yes, I recognize it as HEXADECIMAL, and I could certainly decode it in C but that really wasn't my question.

This was very easy to do on an Arduino so I'll rephrase my question: isn't there an easier way to read this very common device (DS3231 RTC) in NODE RED? Surely someone has done this before.

5

Try this in a function node

var val = msg.payload
msg.payload= ((Math.floor(val/16)*10)+val%16)
return msg;
6

I guess I gotta do what I gotta do.

Thanks for that snippet edje11 ... it decodes and displays perfectly now.

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7

Did you check NPM for a node.js package ? Apparently there are two of them who are up to the job.

8

I did search, but nothing returned. Could you be more specific for my search?

9

Only today I could have a better look on them. Both are lacking a Github repository. It seems to me they are abandoned. You probably did the right choice on handling them directly with I2C node, reading the internal registers.

10

Well, I seemed to have really messed something up. All was working well until I followed some tutorials about how to set the HWCLOCK.

Now, when I scan using 'i2cdetect -y 1' it shows ports 57 and a UU in port 68 where the DS3231 is supposed to be. The 'UU' is supposedly a conflict but the commands 'sudo hwclock -r' and sudo hwclock -w' entered into the terminal seem to work.

Yet using the i2c Scan node, a port 87 appears. I get errors when I try to use the 'i2c in' nodes to connect to 57 or 68. It will connect to the phantom port 87 but I only receive '255' in the msg.

Can someone tell me what I've messed up here?

11

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