Author Topic: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS  (Read 1775 times)

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Offline dendrite

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #25 on: July 31, 2018, 06:47:11 PM »
Not much that I can add, but good work. If you could make the 35 easily plug & play I'd pay for it when the pin 35 is released.

Offline jgentry

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #26 on: July 31, 2018, 08:39:00 PM »
Not much that I can add, but good work. If you could make the 35 easily plug & play I'd pay for it when the pin 35 is released.

Same here!
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Offline mcrossley

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #27 on: August 01, 2018, 02:48:23 AM »
My only question would be power consumption? Power management in the ISS must be pretty tight, would this thing require an external power source?
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Online johnd

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #28 on: August 01, 2018, 04:07:24 AM »
My only question would be power consumption? Power management in the ISS must be pretty tight, would this thing require an external power source?

Davis imply that a cabled ISS consumes 9mA, but I don't know how much of that might be used by the RS422 connection vs turning on the wireless chips every 2.5 secs or so.
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Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #29 on: August 01, 2018, 08:18:50 AM »
My only question would be power consumption? Power management in the ISS must be pretty tight, would this thing require an external power source?

I don't intend to power it from the ISS.  I'm going to use the VCC signal from the ISS to bring the processor out of Sleep mode, let it do it's thing and then go back to sleep.   Perhaps it could be only solar powered and would fit inside a standard wireless Davis ISS enclosure with the solar panel.

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Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #30 on: August 08, 2018, 04:54:53 PM »
Well, I haven't received my SHT35.  In the mean time I wrote some code that reads the SHT75 in a real similar manner that the ISS does.  It is inserted (in txt format) if anyone is interested.  Just copy and paste it into an
Arduino sketch.

 [ You are not allowed to view attachments ]

It is not a final version by no means, but to be used as a diagnostic tool - goes really great with a logic analyzer!

Ray

Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #31 on: August 21, 2018, 07:02:12 PM »
Thanks to SLOweather, I now have a SHT75 connected to my ISS.  I am capturing the real time data in a piggybacked processor.  I am going to let it run for a while to see if it "chokes".

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« Last Edit: August 21, 2018, 07:07:45 PM by rdsman »
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Offline dendrite

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #32 on: August 21, 2018, 09:23:24 PM »
Awesome. Do you have this data online?

Offline galfert

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #33 on: August 21, 2018, 11:28:13 PM »
Nice work on the 75 reader. But I'm looking for an update on the 35 which is the next step in your drop 75 insert 35 data design.  Have you gotten data from the 35 yet?
« Last Edit: August 21, 2018, 11:37:23 PM by galfert »
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Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #34 on: August 22, 2018, 03:56:42 AM »
Awesome. Do you have this data online?

No, but this is the Raw data coming from the SHT75, not what the ISS sends to the console.  The actual temperature and humidity values have to be calculated first.  So the next step is to make sure that I can match what the console is displaying in real time.

Nice work on the 75 reader. But I'm looking for an update on the 35 which is the next step in your drop 75 insert 35 data design.  Have you gotten data from the 35 yet?

Yes, I can read the SHT35. 

Ray

Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #35 on: August 22, 2018, 04:25:19 PM »
Quote
The actual temperature and humidity values have to be calculated first.  So the next step is to make sure that I can match what the console is displaying in real time.

The temperature is dead on every time.  The humidity is exactly 1.0% low when I calculate it based on the captured data.  This is an example:

Console shows 46.
RFBee receiver shows 46.4.
Excel spreadsheet gets 46.4.
Arduino shows 45.4.

??????


Ray

Offline galfert

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #36 on: August 22, 2018, 04:54:06 PM »
Seem like the Arduino has some sort of -1% offset correction going on. Maybe the scale is different. Like maybe you are reading hex codes it is a difference of whether you start at 0 or if you start counting a 1.
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Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #37 on: August 22, 2018, 06:34:23 PM »
Seem like the Arduino has some sort of -1% offset correction going on. Maybe the scale is different. Like maybe you are reading hex codes it is a difference of whether you start at 0 or if you start counting a 1.

Here is my thinking, the console resolution is 1.0% starting at 1.0%.  Maybe the initialized value of RH is set at 1.0% in the ISS because the console can't display tenths of a percent - even though the ISS transmits in tenths.  It would keep the ISS from transmitting values below 1.0%.   Just a thought for now.....


 
Ray

Offline rdsman

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #38 on: August 28, 2018, 04:19:09 PM »
I've made some progress on this project.  While I haven't calculated a percentage of difference between the two, all I can say is most of the time they match each other.  When they differ, is never more than .1 degree in temperature or .1 percent in humidity.

 [ You are not allowed to view attachments ]

Personally, I'd be happy with it the way it is, but I'll see if I can fine tune it.....

I'm amending this to better explain the picture.  The processor is reading the SHT35 and reversing its compensation, calculating what would be expected for the SHT75 and then printing both sets of data out for comparison.
« Last Edit: August 29, 2018, 05:40:50 PM by rdsman »
Ray

Offline jgentry

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #39 on: August 28, 2018, 04:25:30 PM »
I've made some progress on this project.  While I haven't calculated a percentage of difference between the two, all I can say is most of the time they match each other.  When they differ, is never more than .1 degree in temperature or .1 percent in humidity.

 [ You are not allowed to view attachments ]

Personally, I'd be happy with it the way it is, but I'll see if I can fine tune it.....

Awesome! Would love to see how it compares when the RH is in the 90% range, especially near or at 100% Might not be able to do this test, but it would be interesting to see how the temps compare when its below 0F
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Offline CW2274

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #40 on: August 28, 2018, 06:14:29 PM »
I've made some progress on this project.  While I haven't calculated a percentage of difference between the two, all I can say is most of the time they match each other.  When they differ, is never more than .1 degree in temperature or .1 percent in humidity.

 [ You are not allowed to view attachments ]

Personally, I'd be happy with it the way it is, but I'll see if I can fine tune it.....

Awesome! Would love to see how it compares when the RH is in the 90% range, especially near or at 100%
Yes, very impressive. Don't forget us folks at the other end of the spectrum. ;)

Offline galfert

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Re: Convert i2c to sensibus (sensirion) protocol to be read by Davis ISS
« Reply #41 on: August 28, 2018, 07:17:40 PM »
Very nice results. Will you be sharing your code for the drop 75 and replace with 35 data? I can't wait to see that....but if you are keeping it closed source that's cool too.

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