RS232 3 Click is a compact add-on board representing a universal usable RS232 transceiver. This board features the SP3221E, a low-power RS232 transceiver from MaxLinear. The SP3221E uses an internal high-efficiency, charge-pump power supply and is compliant with EIA/TIA-232-F standards when powered by any of the mikroBUS™ power rails. The AUTO ON-LINE® feature allows the SP3221E to automatically "Wake-Up" from a Shutdown state when an RS232 cable is connected and a peripheral device is turned on. When not connected or not in use, the SP3221E will automatically shut down, drawing less supply current. This Click board™ is suitable for low-power serial communications, portable serial devices, point-of-sale equipment, and many more applications.

RS232 3 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.

RS232 3 Click as its foundation uses the SP3221E, a low power, RS232 transceiver (single driver/single receiver) solution with a 250kbps data rate from MaxLinear. The SP3221E uses an internal high-efficiency, charge-pump power supply and is compliant with EIA/TIA-232-F standards when powered by any of the mikroBUS™ power rails. This charge pump and MaxLinear's driver architecture allow the SP3221E to deliver compliant RS-232 performance from a single power supply intended for portable or handheld applications such as embedded computers, data logging devices, medical diagnostics, and remote sensors.

The SP3221E 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 LED indicator labeled as STATUS that indicates whether a valid RS232 signal is present not. This signal is also routed to the INT pin of the mikroBUS™ socket, labeled as STA. Alongside UART communication, several signals connected to the mikroBUS™ socket pins are also used to forward the information to the MCU.

For proper operation of SP3221E, this board uses a combination of two pins, EN and SHD pins routed to the CS and RST pins of the mikroBUS™ socket. The receiver is active when the AUTO ON-LINE® circuitry is enabled or when in Shutdown. The AUTO ON-LINE® feature, controlled via ON pin routed to the PWM pin of the mikroBUS™ socket, allows the SP3221E to automatically "Wake-Up" from a Shutdown state when an RS232 cable is connected, and a peripheral device is turned on. During the Shutdown, the receiver will continue to be active. If there is no activity at the receiver for a more extended period or when the SHD pin is enabled, the device goes into a Standby mode. Also, driving the EN pin to a high state forces the receiver's output into a high impedance state.

This Click board™ can operate with both 3.3V and 5V logic voltage levels selected via the VCC SEL jumper. This way, it is allowed for both 3.3V and 5V capable MCUs to use the communication lines properly. However, the Click board™ comes equipped with a library that contains easy-to-use functions and an example code that can be used, as a reference, for further development.

• Interface: UART
• Compatibility: mikroBUS™
• Dimensions: 57.15 x 25.4mm
• Input Voltage: 3.3V or 5V
• Data Rate: 250 kbps
• Operating Temperature Range: Min. -40°C, Typ. +25°C, Max. +85°C

• Schematic
• SP3221E Datasheet
• mikroSDK
• GitHub