influxdata/telegraf

Modbus Data_Type = "BCD"

Open

#15,925 opened on Sep 22, 2024

View on GitHub
 (8 comments) (0 reactions) (0 assignees)Go (9,892 stars) (4,161 forks)batch import
area/modbusfeature requesthelp wantedsize/s

Description

Use Case

Hi. A Modbus device delivers some Registers as data_type = BCD. For example the "Date & Time" information via 3 Bytes (24bit) as BCD.

So far, I did not find a way to decode these registers :-(

Question is: Is there a way to decode BCD coded registers? or could this become a new feature??

Thanks for your the brillliant "Telegraf" Cheers Jurgen

Expected behavior

Decode for example: Read 3-bytes and assign 4-bits per digit and assign 2 digits to the 1st number ( e.g.: the day) assign 2 digits to the 2nd number (e.g.: the month) assign 2 digits to the 3rd number ( e.g. 2 digit year) etc.

Actual behavior

??

Additional info

No response

Contributor guide

Tech stack
go
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Go programmingTelegraf plugin structureModbus protocol basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
The issue requests adding BCD decoding support in the Modbus input plugin. The implementation likely involves extending the data type conversion logic in `plugins/inputs/modbus/` (e.g., in `field.go` or `converter.go`). Look for existing handling of similar types like INT32 or FLOAT, and add a new BCD type that reads bytes and decodes each nibble as a digit. The maintainers may have discussed specific byte offsets and endianness; review the comments for any clarifications. The existing test files in the same directory should be updated to cover BCD parsing.