E1.20 RDM (Remote Device Management) Protocol Forums  

Go Back   E1.20 RDM (Remote Device Management) Protocol Forums > RDM Developer Forums > RDM Interpretation Questions

RDM Interpretation Questions Discussion and questions relating to interpreting and understanding the E1.20 RDM Standard.

Reply
 
Thread Tools Search this Thread Display Modes
Old April 9th, 2021   #1
FishAI
Junior Member
 
Join Date: Jul 2019
Posts: 6
Default E1-20: Sensor Values With Base 2

Hello all you great girls and guys,

please help me out again.

Recently my colleague and I discussed one interesting bit of the E1-20 standard. Beneath Table A-14 is the following annotation:
"When a prefix is used with MEMORY, the multiplier refers to binary multiple. i.e. KILO means multiply by 1024."

We had a great argument about this note.
From our understanding this refers to the interpretation of the sensor value received by SENSOR_VALUE, not the representation of this value.
For example, a sensor reporting a present value of 1 with the sensor's prefix being PREFIX_KILO, the sensor reports a true value of 1024 bytes.
It is not reporting 1000 (true) bytes, which should be represented as ~0.98 kibibyte.

However, we did not figured out whether the multiple of 1024 is only valid if and only if the Sensor Type is SENS_MEMORY.
SENS_MEMORY seems to be the closest match to the mentioned MEMORY, but we are unsure whether the standard does mean any memory related types or indeed solely SENS_MEMORY.

For example manufacturer specific parameters using UNITS_BYTE is a big question here. Should the prefix there also be based on the binary multiple?
Or should a device using manufacturer specific parameters report 1024 UNITS_BYTE to mean 1 kibibyte?

If the binary base refers only to SENS_MEMORY:
Does this mean, that any SENSOR_DEFINITION with its sensor type being different from SENS_MEMORY but its unit being UNITS_BYTE, should NOT use 2 as its base?

Also, there is the special case of exponents being less than 1. What would you expect, if any device reports the following values:
SENSOR_DEFINITION: SENS_MEMORY, UNIT_BYTE, PREFIX_MILLI
SENSOR_VALUE: PresentValue: 0x00000120
Obviously the device reports some sort of undefined partially byte. But would you expect a value of 0.288 millibyte or something different?
We do not know any defined prefix for base 2 with the exponent being less than 1 (like kibi for the exponent being 3). Are there any?

What is the correct interpretation of the mentioned note, what are you recommendation?

Best regards,
FishAI
FishAI is offline   Reply With Quote
Old April 11th, 2021   #2
sblair
Administrator
 
Join Date: Feb 2006
Posts: 429
Send a message via AIM to sblair Send a message via MSN to sblair
Default

Fish,

You raised some very good questions. These are questions we will need to clarify in a future revision to the standard.

I went back to Wayne Howell who wrote that portion of the original document. Here's his comments on the original thinking:

Quote:
For SENS_MEMORY or any sensor type using UNITS_BYTE, the prefix is 1024. So using the commenter’s example:

No Prefix - 1024 UNITS_BYTE = 1024 bytes = 1 Kbyte
Kilo prefix - 1 UNITS_BYTE = 1024 bytes = 1 Kbyte
Kilo prefix - 1000 UNITS_BYTE = 1000 Kbytes
Kilo prefix - 1024 UNITS_BYTE = 1 Mbyte

Using milli etc was never considered and should be thought of as undefined.
__________________
Scott M. Blair
RDM Protocol Forums Admin
sblair is offline   Reply With Quote
Old April 12th, 2021   #3
FishAI
Junior Member
 
Join Date: Jul 2019
Posts: 6
Default

Hi sblair,

Thank you for the quick reply and for contacting the original author.
We are looking forward to seeing this clarified in future revisions.
Until then, we would probably use the factor 1024 when a value has the unit UNITS_BYTE, as it was surely intended by Mr. Howell.

Best regards,
FishAI
FishAI is offline   Reply With Quote
Old 3 Weeks Ago   #4
peternewman
Junior Member
 
Join Date: Oct 2018
Location: London
Posts: 11
Default

Quote:
Originally Posted by FishAI View Post
Recently my colleague and I discussed one interesting bit of the E1-20 standard. Beneath Table A-14 is the following annotation:
"When a prefix is used with MEMORY, the multiplier refers to binary multiple. i.e. KILO means multiply by 1024."
I suspect you'll find most controllers are probably just concatenating the PREFIX and UNIT fields together, so the multiplier is more for the device end to ensure it sends the correct value, i.e. you need to divide your bytes measurement by 1024 to get the value you send to the controller.


The real edge case here is if they show mkg or g for grammes!


Quote:
Originally Posted by FishAI View Post
Also, there is the special case of exponents being less than 1. What would you expect, if any device reports the following values:
SENSOR_DEFINITION: SENS_MEMORY, UNIT_BYTE, PREFIX_MILLI
SENSOR_VALUE: PresentValue: 0x00000120
Obviously the device reports some sort of undefined partially byte. But would you expect a value of 0.288 millibyte or something different?
We do not know any defined prefix for base 2 with the exponent being less than 1 (like kibi for the exponent being 3). Are there any?
Quote:
Originally Posted by sblair View Post
I went back to Wayne Howell who wrote that portion of the original document. Here's his comments on the original thinking:Using milli etc was never considered and should be thought of as undefined.

Couldn't you use 128 millibytes (miB) to represent a bit?!
peternewman is offline   Reply With Quote
Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Sensor type and Sensor unit for No of Phases question berntd RDM General Implementation Discussion 1 October 1st, 2009 10:04 PM
Sensor type and Sensor unit for DMX rate question berntd RDM General Implementation Discussion 3 October 1st, 2009 12:41 AM
SC_SUB_MESSAGE values Brian Sidebotham RDM Interpretation Questions 5 August 7th, 2006 05:37 PM


All times are GMT -6. The time now is 09:33 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2021, vBulletin Solutions, Inc.