RS232 Isolator 2 Click Board™

How Does The RS232 Isolator 2 Click Board™ Work?

The RS232 Isolator 2 Click Board™ as its foundation uses the ICL3221, a 3.3V powered RS232 transmitter/receiver that provides ±15kV ESD protection on its RS232 pins from Renesas. It features an automatic power-down function that occurs when the RS232 cable is removed and conserves system power automatically, and power-up again when a valid RS232 voltage is applied to any receiver input. It also ensures data rates greater than 250kbps even at worst-case load conditions.

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The RS232 Isolator 2 Click Board™ represents an isolated RS232 interface configuration using PS9121, an optically coupled high-speed active-low type isolator from Renesas, containing a GaAlAs LED on the input side, a photodiode, and a signal processing circuit on the output side rated for 3.75kV isolation and up to 15Mbps data rate. The RS232 transceiver ICL3221 is specified with a data rate of 250kbps and operates from a 3.0V to 3.6V external power supply header on the board's right side. In addition to the optocouplers, the TC7SZ125FU logic buffers from Toshiba Semiconductor are used to drive the necessary LED currents that usually cannot be provided by low-power MCUs or RS232 receiver outputs.

The ICL3221 communicates with MCU using the UART interface with the default baud rate of 115200bps for the data transfer. It also comes equipped with the standard DB-9 connector, which makes interfacing with the RS232 simple and easy, and a red diode indicator labelled as INVALID indicates whether a valid RS232 signal is present or not.

This diode always indicates whether a valid RS232 signal is present at any of the receiver inputs, giving the user a way to determine when the interface block should power down. If the interface cable is disconnected from the DB-9 connector and all the receiver inputs are floating, the ICL3221 detects invalid levels turning the LED. Reconnecting the cable restores valid levels at the receiver inputs, the diode turns off, and the power management logic wakes up the interface block.

The RS232 Isolator 2 Click Board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before use with MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.

SPECIFICATIONS

PINOUT DIAGRAM

This table shows how the pinout of the RS232 Isolator 2 Click Board™ corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin	​				Pin	Notes
NC	1	AN	PWM	16	NC
NC	2	RST	INT	15	NC
NC	3	CS	RX	14	TX	UART TX
NC	4	SCK	TX	13	RX	UART RX
NC	5	MISO	SCL	12	NC
NC	6	MOSI	SDA	11	NC
Power Supply	3.3V	7	3.3V	5V	10	NC
Ground	GND	8	GND	GND	9	GND	Ground

ONBOARD SETTINGS AND INDICATORS

RS232 ISOLATOR 2 CLICK ELECTRICAL SPECIFICATIONS