Softwareserial.h Library -

// Find this line: #define _SS_MAX_RX_BUFF 64 // Change to 128 or 256 (uses more RAM) Don't. Both rely on precise timing and disabling interrupts. They are incompatible. Use hardware serial or an I2C/SPI serial bridge (e.g., SC16IS750). 10. Alternatives to SoftwareSerial | Alternative | Pros | Cons | |-------------|------|------| | HardwareSerial (Serial1, Serial2 on Mega) | Reliable, full-duplex, high speed | Limited ports | | AltSoftSerial (Paul Stoffregen) | Better timing, supports 57600 baud | Fixed pins (8=RX, 9=TX on Uno) | | NeoSWSerial | Interrupt-driven, allows multiple RX | Still software-based | | I2C/SPI UART modules (e.g., MAX3100) | Frees CPU, many ports | Extra hardware cost | | Use a second Arduino as serial bridge | Very flexible | Complex, power hungry | 11. Full Example: GPS + Bluetooth on Uno #include <SoftwareSerial.h> SoftwareSerial gps(10, 11); // GPS module SoftwareSerial bluetooth(8, 9); // HC-05 Bluetooth

1. Introduction: The Hardware Limitation Every Arduino enthusiast eventually hits the wall: "I only have one hardware serial port (pins 0 and 1), but I need to connect two serial devices."

// Must call listen() on active port regularly if (!gps.isListening()) gps.listen(); softwareserial.h library

SoftwareSerial port1(2, 3); SoftwareSerial port2(4, 5); void setup() port1.begin(9600); port2.begin(9600); port1.listen(); // port1 is active

void checkForData(SoftwareSerial &ss) ss.listen(); if (ss.available()) // Process // Find this line: #define _SS_MAX_RX_BUFF 64 //

The classic Arduino Uno, Nano, and Mega 2560 (for its first few ports) have dedicated hardware UARTs (Universal Asynchronous Receiver-Transmitters). However, hardware UARTs are limited in number. Once you connect a GPS module, a Bluetooth module, and a debug console simultaneously, you run out of ports.

Bidirectional Communication with Collision Avoidance Since SoftwareSerial is half-duplex, implement a simple protocol: Use hardware serial or an I2C/SPI serial bridge (e

void loop() if (gps.available()) char c = gps.read(); Serial.print(c); // Echo GPS data to Serial Monitor