4N35 – a general purpose optocoupler that consists of a gallium arsenide infrared emitting diode driving a silicon phototransistor in a 6-pin dual in-line package used in microprocessor inputs, digital logic inputs, and power supply regulators due to its features such as high isolation voltage between input and output, operating temperature up to +110✬, and available in wide-lead spacing.

BC550 – an NPN general purpose transistor with low current and low voltage used for low noise stages in audio frequency equipment.

A value of 0xFF permanently enables the pin when configured in this way, it will always reflect the RSSI value of the last-received data packet.The circuit has been designed for telephone apparatus to indicate an incoming call as it rings using an LED for visual indication. The pin will also be set to low at power-up until the first data packet is received. For example, a configured value of 0x1E is equivalent to 30 in decimal and means that the pin will be active for three seconds (30*100=3000ms.) So the LED will light for a total of three seconds, representing the last RSSI value.Īfter the RP time has elapsed and no data has been received, the pin will be set to low and the LED will not light until more data is received. RP value is expressed in hexadecimal notation. Its intensity represents the RSSI value of the last-received data: a brighter light means a higher RSSI value and better signal quality.Ĭonfigure the amount of time the RSSI pin is active, and therefore the amount of time the LED will remain lit, by modifying the RSSI PWM Timer (RP) setting: When this pin is configured as the RSSI pin, the LED lights every time the connected XBee module receives data. The XBee Grove Development Board includes an LED connected to the XBee module's pin 6. XBee module's pin 6 can be configured as an RSSI pin that outputs a PWM (pulse-width modulation) signal representing this value. Therefore, -50 dBm is better than -60 dBm. A greater negative value (in dBm) indicates a weaker signal. Likewise, if a transmitter is moved farther away, signal strength at the receiving antenna decreases. If a distant transmitter is moved closer to a receiver, the strength of the transmitted signal at the receiving antenna increases. Measuring the signal strength at the receiving antenna is one way to determine the quality of a communication link.

It is an approximate value for signal strength received on an antenna.

The Received Signal Strength Indicator (RSSI) measures the amount of power present in a radio signal.

Ring indicator pin