> For the complete documentation index, see [llms.txt](https://inacks.gitbook.io/inacks-is3720-i2c-dmx+rdm-receiver-ic/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://inacks.gitbook.io/inacks-is3720-i2c-dmx+rdm-receiver-ic/datasheet/pins.md).

# Pins

<figure><img src="https://4031855160-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FMR1I6AmpcBW5WamvgJ4O%2Fuploads%2FLQWHPIP15P4vSMJxugoB%2FEvadrw00103r1.png?alt=media&amp;token=2a60be11-7779-4fc2-ad94-79db5bba0f00" alt="" width="270"><figcaption></figcaption></figure>

<table><thead><tr><th width="73">Pin</th><th width="110">Name</th><th width="144"></th><th>Description</th></tr></thead><tbody><tr><td>1</td><td>SDA</td><td><p>Open-Drain</p><p>5 V-Tolerant</p></td><td>I2C data pin. Connects to your microcontroller. Open‑drain pin; a pull-up resistor is required.</td></tr><tr><td>2</td><td>VDD</td><td>Supply</td><td><p>3.3 V power supply pin.</p><p>Bypass this pin to VSS with a 100 nF and 2.2 μF ceramic capacitors. Place them as close as possible to the IC.</p></td></tr><tr><td>3</td><td>VSS</td><td>Supply</td><td>0 V reference pin.</td></tr><tr><td>4</td><td>DIR</td><td><p>Output</p><p>Open-Drain</p><p>5 V-Tolerant</p></td><td><p>DMX+RDM UART Direction Pin. Open‑drain pin; a pull-up resistor is required.</p><p>Connect this pin to the Driver Enable (DE) and Receiver Enable (RE) pins of the RS485 transceiver, with a pull‑up resistor connected to the transceiver supply voltage.</p></td></tr><tr><td>5</td><td>RX/TX</td><td><p>Input-Output</p><p>Open-Drain</p><p>5 V-Tolerant</p></td><td><p>DMX+RDM UART receive and transmit pin at TTL voltage levels.</p><p>Connect this pin to the Receiver data Output (RO) and Driver data Input (DI) pins of the RS485 transceiver, with a pull‑up resistor connected to the transceiver supply voltage.</p></td></tr><tr><td>6</td><td>INT</td><td><p>Output</p><p>Push-Pull</p></td><td><p>Interruption pin. This pin can optionally be connected to your microcontroller to notify changes to</p><p>DMX_START_ADDRESS or IDENTIFY_DEVICE registers.</p></td></tr><tr><td>7</td><td>I2CSPD</td><td><p>Analog Input</p><p>0 to 3.3 V</p></td><td><p>I2C-Serial Interface Speed Selection pin.</p><ul><li>For 100 kHz pull to VSS.</li><li>For 400 kHz make a voltage divider of VDD/2 (1.65 V).</li><li>For 1 MHz pull to VDD (3.3 V).</li></ul></td></tr><tr><td>8</td><td>SCL</td><td><p>Open‑Drain</p><p>5 V-Tolerant</p></td><td>I2C clock pin. Connects to your microcontroller. Open-drain; requires a pull-up resistor.</td></tr></tbody></table>

### RX/TX and DIR Pins <a href="#refheading___toc23978_752506811" id="refheading___toc23978_752506811"></a>

DMX+RDM UART Communication Pins.

DMX+RDM communication is half-duplex; therefore, devices connected to this interface can operate either in receive or transmit mode, but not both simultaneously.

Since the communication is half-duplex, a single RX/TX pin is used for both reception and transmission, along with a data direction (DIR) pin.

An RS485 transceiver (e.g., THVD1500) is required to convert the logic levels of RX/TX pin to DMX+RDM (RS485) differential signals.

Both RX/TX and DIR pins are open‑drain and require a pull-up resistor to the same supply voltage that the transceiver is working, typically 3.3 V or 5 V.

The RX/TX pin is connected to both the Driver data Input (DI) and the Receiver data Output (RO) of the RS485 transceiver.

The DIR pin controls the data direction. It is set high when the TX/RX pin is transmitting and low when receiving. This pin is connected to both the DE (Driver Enable) and RE (Receiver Enable) pins of the RS485 transceiver.

Using 5 V transceivers is preferred, as they provide better noise immunity and support longer cable lengths.

Refer to the Hardware Examples section for more details.

### INT Pin <a href="#refheading___toc115816_4215993856" id="refheading___toc115816_4215993856"></a>

Interruption Pin.

This pin generates a positive pulse whenever the DMX\_START\_ADDRESS (70 ms) or IDENTIFY\_DEVICE (50 ms) registers are modified.

Since these registers need be monitored for changes, this pin allows the microcontroller to avoid continuously polling them via I2C and instead relay on the pin status.

### SCL and SDA Pins <a href="#refheading___toc23982_752506811" id="refheading___toc23982_752506811"></a>

I2C-Serial Interface Pins.

SCL (Serial Clock Line): This pin is used to synchronize data transfer between the IS3720 device and your microcontroller or other CPU.

SDA (Serial Data Line): This bidirectional pin is used for both sending and receiving data between the IS3720 and your microcontroller..

Both pins are open-drain and must be pulled up to 3.3 V or 5 V. The pull-up resistor value should be chosen based on the bus speed and capacitance. Typical values are 4.7 kΩ for Standard Mode (100 kHz) and 2 kΩ for Fast Mode and Fast Mode Plus (400 kHz and 1 MHz).

### I2CSPD Pin <a href="#refheading___toc23984_752506811-copy-1-copy-1" id="refheading___toc23984_752506811-copy-1-copy-1"></a>

I2C-Serial Interface Speed Selection Pin.

This pin configures the IS3720 internal I2C-serial Interface timings and filters to properly work with the selected bus speed.

For a 100 kHz setting, set the I2CSPD pin to VSS.

\
For a 400 kHz setting, set the I2CSPD to 1.65 V (VDD/2) using a balanced voltage divider. This can be achieved by placing two 4.7 kΩ resistors from the I2CSPD pin: one to VDD and the other to VSS.

\
For a 1 MHz setting, set the I2CSPD pin to 3.3 V.


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