Connecting Arduinos using SoftwareSerial

In tutorial three we used three LEDs, a potentiometer and an Arduino as a status indicator

Now we want to implement the same functionality using two Arduinos

Connect the LEDs and Potentiometer as described in tutorial three

Verify that the hardware setup works using one of the working code examples

For the next tasks we will need two Arduinos

Assemble in groups and decide who will write code for the sending / receiving unit

The sending unit should take the analog values from the potentiometer, encode them and transfer them using SoftwareSerial on pins 2 and 3

Use the code from tutorial three and the code from the lecture as a reference

Hint: You can still use Serial.print for debugging

The receiving unit should read values using SoftwareSerial on pins 2 and 3, decode them and turn on the corresponding LEDs

Use the code from tutorial three and the code from the lecture as a reference

Hint: You can still use Serial.print for debugging

Sender / Receiver

high ─┐ ┌─────┐     ┌──────
      │ │     │     │
low   └─┘     └─────┘
bit#   S 0 1 2 3 4 5 6 7 E

The baud rate is the number of symbols that are transmitted per second

A symbol can be the start bit, a data bit, a stop bit or a parity bit

The defaults are 9600Bd, one start bit, eight data bits, no parity bit and one stop bit

high ─┐ ┌─────┐     ┌──────
      │ │     │     │
low   └─┘     └─────┘
bit#   S 0 1 2 3 4 5 6 7 E

Write a sender that uses digitalWrite and delayMicroseconds to transfer the data

Hint: The following slides contain more hints should you get stuck

1 pinMode(3, OUTPUT);
2 digitalWrite(3, s);

The software serial port used pin 3 as TX line,

this is where data should be sent

1 void uart_bit_send(boolean s)
2 {
3   digitalWrite(3, s);
4   delayMicroseconds(104);
5 }

9600 Symbols are transmitted per second,

this means that the transmission of one symbol takes 1s/9600 ≈ 104µs

1 uart_bit_send(LOW);
2 // Transfer data
3 uart_bit_send(HIGH);

The transmissions start with a 0 (start bit) and ends with a 1 (stop bit)

1 uart_bit_send(LOW);
2 for(uint8_t b=0; b<8; b++) {
3   uart_bit_send(defcon & 0x01);
4   defcon>>=1;
5 }
6 uart_bit_send(HIGH);

…