August 24, 2018 at 2:51 pm #1524
I have the following questions:
1) Is there a data sheet for RFM3200? I need more functional detail than what is included in the brochure and the application notes.
2) Can the auto-tuning feature of the RFM3200 be disabled?
3) How many different settings or levels or steps are there to the auto-tuning feature?
4) Can the number of steps be decreased or restricted?
5) What is the timing for the auto-tuning per the number of steps?
6) I need to take a temperature reading from multiple tags once or twice per second. How can I select a specific tag to respond with its temperature, instead of all the tags responding on each cycle?
Steve0August 28, 2018 at 7:27 pm #1526
Greg PitnerRFMicron Team Member
I may not be able to fully answer your questions in this format. I’ll make an attempt, but please feel free to contact us at email@example.com for anything I don’t cover below.
First, just to make sure we’re on the same page, the Sensor Code (which essentially reports the outcome of the auto-tuning process) is distinct and independent of the Temperature Code.
To target a specific tag, you can use a Select command which specifies a particular EPC. Your reader will have to be capable of sending at least 2 Select commands in each inventory (communication cycle), since you will also need one to activate the temperature calculation on the tag(s). The specific details on how to do this will depend on the reader you’re using.
The Sensor Code is a 9-bit value, so it theoretically varies from 0 to 511. In practice, due to some subtleties in how it works, the values will not generally swing quite that far — usually they will range from around 5 to around 490. The auto-tuning process happens as soon as the tag wakes up and before any formal communication is established with the reader, so it doesn’t impact temperature reading in any way.
This process can’t be adjusted or deactivated. We do make a temperature-sensing chip that does not have auto-tuning, but it is currently only available on a different kind of tag: the RFM3240. If you can share what you trying to achieve by making the auto-tuning work differently, then we might be able to offer some advice.
Greg0September 5, 2018 at 2:46 pm #1528
Thanks, Greg. Can you send me the data sheet for the RFM3200?
I need to read temperatures from 5o-60 tags every 0.5-1 sec. In order to achieve that fast of a read cycle time, I’ve characterized my sensor array to determine the optimal reader power settings for every tag. I’m now attempting to step through the optimal power settings for each individual or group of tags to take successive temperature readings as fast as I possibly can. Please let me know if you think there’s a better way of doing this.0September 6, 2018 at 11:57 am #1529
Another question: What is the translation formula to convert RSSI value and actual power level (dBm)?0September 7, 2018 at 7:14 pm #1530
Greg PitnerRFMicron Team Member
Please see the documentation for the 3200 on the website, and contact firstname.lastname@example.org if you need additional information.
Your transmit power strategy sounds good, but I suspect it will be pretty difficult to achieve that sample rate. You might also consider using Select commands to choose specific subsets of the tag population that all need the same power level. That way you are only trying to talk to tags that have optimized power levels.
There’s not really a precise mapping between On-Chip RSSI and power levels in dBm. If a tag reports an On-Chip RSSI of 1, then it just barely has enough power to operate. If it reports a value of 31, it is receiving very roughly 15 dBm more power than needed to turn on.0
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