multiIO / Supported devices / SMA
SMA standard protocol
The Scale Manufacturers Association's Standard Scale Serial Communication Protocol — the one entry in this catalogue that belongs to no manufacturer. Its stated purpose is to make the method of scale communication common across all scale manufacturers, so any conformant indicator decodes against a single parser.
2
Compliance levels
1
Output formats
2
Catalogue entries
⚠ These are protocol compliance levels, not scale models, and we do not count them as supported indicators. Where a vendor's own manual names SMA on a specific model, that model gets an entry in that vendor's suite as well — Cardinal's does. Both routes decode the same bytes; they differ in what the reading's identity says downstream.
Models and the formats they offer
| Model | Output formats | Default baud |
|---|---|---|
| SMA Level 1 | Standard ★ | 9600 |
| SMA Level 2 | Standard ★ | 9600 |
The formats
Each one is a separate parser, because which format a site chose is not reliably detectable from the stream — you pick what the box's own menu is set to. Example frames below are produced by that format's own encoder and read back through its own parser.
Standard
The SMA standard response message
A complete, fixed-field specification: a scale status character, a range character, gross/net, motion, a reserved character, a ten-character weight field and a three-character unit field with a 28-entry abbreviation table. Levels 1 and 2 differ in which commands a scale answers, not in what the response looks like.
⚠ The scale never speaks first — the host is always the commanding device and the scale never sends unsolicited responses. Two commands do stream, but both must be sent first, and the gateway's input side is receive-only today, so a real SMA deployment needs the port primed externally until that changes. On the emulation side there is no such problem: there the gateway is the scale answering polls. Error conditions fill the weight field with dashes and carry no weight at all rather than being labelled as a range condition.
Example frame — SMA Level 1, a stable 12.34 kg gross reading
<LF>·1G······12.340kg·<CR>
0A 20 31 47 20 20 20 20 20 20 31 32 2E 33 34 30 6B 67 20 0D
20 bytes · decodes back to 12.34 kg
Verified against: SMA SCP-0499, first edition April 1999, Mod 1 November 2005, §5.1 with the command sets at §6.1 and §6.2
Is your indicator here?
If it is, it works out of the box — pick the model and the format its menu is set to, and readings publish over MQTT, Modbus TCP, OPC UA, REST and six more transports at once. If it is not, describe the line's fields in the console and multiIO decodes it anyway, or send us the manual's serial chapter: that is how most of this catalogue got here.