RDM Responder – IS3720

The IS3720 unlocks the full power and flexibility of the RDM protocol—with zero libraries required. Everything is managed through a simple I2C interface. It’s the easiest way to make your product RDM-compatible. The chip receives DMX data and responds to RDM queries, all handled internally.

How It Works

The chip features two ports:

• I2C Interface: Connects to your microcontroller, FPGA, Arduino, Raspberry Pi, etc. You read the DMX values and configure RDM parameters directly through its memory map.
• UART Output: Connects to your RS485 transceiver. The IS3720 sends and receives DMX and RDM data at TTL levels, so an RS485 transceiver is required. We like the THVD1400 for its robustness and great value, but you’re free to use whatever suits your design.

Advantages and Features

Firmware Advantages

• Forget about RDM protocol handling: No need to deal with frame parsing, timings, or UART interrupts
• No libraries needed: Just use standard I2C functions
• Buffers all 512 DMX channels (a full DMX universe) — no need to refresh DMX data
• Perfect for heavily loaded CPUs or ISR-heavy applications
• Arduino, STM32, and Raspberry Pi examples available
• Evaluation board available to make some tests
• Save firmware engineering time

Hardware Advantages

• Save pins on your microcontroller: No need to sacrifice any UART pins as it uses I2C, a shared interface
• Reduce the CPU load of your microcontroller
• Reduce Flash and RAM memory footprint
• Save microcontroller resources (UART, Timers, etc.)
• Schematic design examples available

Compatibility Advantages

• Great for non-deterministic systems (like Raspberry Pi and single-board computers)
• Compatible with 5V I2C serial interfaces
• Compatible with 5V RS485 transceivers
• Supports I2C speeds: 100kHz, 400kHz, and 1MHz
• Ideal for FPGA designs

Production Advantages

• Easy-to-solder SO8N package
• Reels available for pick-and-place machines

Commercial Advantages

• Speeds up development
• Faster prototyping
• Shorter time-to-market