DC2209A1

LTC2983 Temperature Module

ESPHome firmware and KiCad hardware designs for reading precision temperature sensors through the Analog Devices LTC2983 — a 20-channel multi-sensor ADC supporting RTDs, thermocouples, diodes, and thermistors.

This chip is complicated. There are lots of variables, especially when you're talking about two and four wire RTD's. Lots of options are available for RTD's with four wires as opposed to two. I'll leave it to you to experiment with excitation current, etc. there are optimizations that can be done that greatly enhance the accuracy and repeatability of measurements that I've discovered, but I'm not going to go into all the gory details as that's for you to discover. This repository will get you a working configuration. Good luck! Oh, and there are some mistakes on the schematic, but you can find those because they are incorrect routing and or things that are not connected, like channel 20 that goes to the PNP transistor. That trace was neglected by mistake.

This repo is a standalone ESPHome device that reads 5× PT1000 RTDs and 5× K-type thermocouples in one multi-channel conversion cycle, with per-channel fault sensors. The board and can be adapted to other sensor combinations on unused LTC2983 channels.

Hardware

SPI wiring (ESP32-S3 → LTC2983)

Channel map

Shared excitation: CH2 = 2 kΩ sense resistor (RSENSE hub). Odd channels CH3/5/7/9/11 tie to CH2. Cold-junction compensation uses a 2N3906 diode on CH20 (emitter → CH20, base + collector → COM).

See schematics/dc2210a-5rtd-5tc-wiring.png and schematics/dc2210a1-sch.pdf for full wiring of demo circuit or KiCad schematics for this implementation.

Firmware

The LTC2983 is driven by a custom C++ handler included directly in the ESPHome config — no external component package required.

Polling uses non-blocking read_ltc2983_sensors(): start a multi-channel conversion (~2 s), publish all channels when DONE, then start the next cycle.

Home Assistant entities

Temperature sensors

• RTD CH4 … RTD CH12 — RTD 1–5 (°C)
• TC 1 … TC 5 — thermocouples (°C)

Fault text sensors (one per channel — OK, Open Circuit, Overrange, etc.)

• Fault CH4, Fault CH6, Fault CH8, Fault CH10, Fault CH12
• Fault TC1 … Fault TC5

Project layout

LTC2983_Temp_Module.yaml   # ESPHome config
ltc2983_handler.h          # LTC2983 SPI driver
common/wifi.yaml           # WiFi package
schematics/                # Wiring diagrams and reference schematics
KiCad/                     # DC2209A1 carrier board (sch, pcb, gerbers)
Demo Circuit Board/        # Analog Devices DC2209A reference files
LTC2983 sketch and info.c  # Reference channel-config notes

Getting started

Prerequisites

• ESPHome installed
• ESP32-S3-DevKitC-1 connected via USB
• LTC2983 board wired per SPI table and channel map above

Secrets

Create secrets.yaml in the project root (gitignored):

wifi_ssid: "YourSSID"
wifi_password: "YourPassword"

Build and flash

Copy to /tmp before running ESPHome (avoids path issues):

cp -r "./LTC2983_Temp_Module" /tmp/ltc2983-temp-module/
cd /tmp/ltc2983-temp-module
esphome run LTC2983_Temp_Module.yaml --device /dev/cu.usbserial-XXXX

Replace /dev/cu.usbserial-XXXX with your serial port. Logs stream automatically — do not use --no-logs.

Home Assistant

Add the device through the ESPHome integration after flashing. All 10 temperature sensors and 10 fault sensors appear under the ltc2983-temp-module device.

References

• LTC2983 datasheet
• DC2210A demo board — 5 RTD + 5 TC reference
• DC2296A evaluation kit
• schematics/dc2210a1-sch.pdf — DC2210A schematic
• schematics/dc2213a1-sch.pdf — DC2213A schematic (single RTD demo)
• KiCad/Gerbers/ — fabrication outputs for the DC2209A1 carrier board