the isue is l've no datasheet and the closest virsion of the sensor l saw was SN-3002-TR-ECTHNPKPH-N01, which l'm not sure if the addressing for common components is the same,
l'd really appreciateany form of assistance given
the isue is l've no datasheet and the closest virsion of the sensor l saw was SN-3002-TR-ECTHNPKPH-N01, which l'm not sure if the addressing for common components is the same,
Most, if not all of those sensors are fraudulent, especially the ones labeled NPK.
The only quantities you can measure with metal rods are temperature and soil conductivity, and many people find that the conductivity measurements are so erratic as to be useless.
Your topic does not indicate that you're trying to interface something with a computer and hence has been moved to a more suitable location on the forum.
at this point I'm wondering if its working at all, so if you may assist on how l can access those parameters
Why buy a sensor with no data sheet, no installation or operating instructions, no support?
l didn't know until l received the sensor
Two sensible options are to ask the seller for information, or better, return it.
oky I'll try that l also heard of trail method, but l'm not sure how its done
A simple search of these forums for "NPK" should provide many hits as this type of sensor appears quite frequently here when used with an Arduino UNO or one of the ESP boards.
The problem you will have is that there are quite a few variants of this sensor that all look the same but some use different register addresses for the parameters that they claim to measure. Without the datasheet specific to your sensor, you would be guessing what parameter is being reported back when the sensor acknowledges a valid register address.
thank you, let me try to talk to the supplier for the datasheet
Some time ago, while helping someone here, I was wondering why the addresses for N,P and K are read/write type.
Then I saw description of one supplier:
NPK storage.The normal use method is that you measure NPK by other methods and then write the data to the device through RS485 command.
It cannot be measured actually, because the nitrogen, phosphorus and potassium values measured by the equipment are not used as a reference. It is ok if it is only for project acceptance.
Which makes sense. Unfortunately most suppliers "forget" to mention that...
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If they are not able to provide datasheet for that specific model, use it as runaround for return/refund. And use completely free random() function on your code to get NPK values... 
Yep, cheaper and equally useful.
Datasheet is here
NPK_7IN1_DATASHEET.pdf (408.1 KB)