// ===================================================================================
// Project: TinyPocketRadio - FM Tuner based on ATtiny13A
// Version: v1.0
// Year: 2020
// Author: Stefan Wagner
// Github: https://github.com/wagiminator
// EasyEDA: https://easyeda.com/wagiminator
// License: http://creativecommons.org/licenses/by-sa/3.0/
// ===================================================================================
//
// Description:
// ------------
// This code implements a simple Pocket Radio with three control buttons
// (Vol+/- and Channel Seek). The FM tuner IC RDA5807MP is controled via
// I²C by the ATtiny.
//
// The I²C protocol implementation is based on a crude bitbanging method.
// It was specifically designed for the limited resources of ATtiny10 and
// ATtiny13, but should work with some other AVRs as well. Due to the low
// clock frequency of the CPU, it does not require any delays for correct
// timing. In order to save resources, only the basic functionalities which
// are needed for this application are implemented. For a detailed
// information on the working principle of the I²C implementation visit
// https://github.com/wagiminator/attiny13-tinyoleddemo
//
// The code utilizes the sleep mode power down function to save power.
// The CPU wakes up on every button press by pin change interrupt, transmits
// the appropriate command via I²C to the RDA5807 and falls asleep again.
//
// Wiring:
// -------
// +-\/-+
// --- RST ADC0 PB5 1|° |8 Vcc
// I2C SDA ------- ADC3 PB3 2| |7 PB2 ADC1 -------- VOL+ BUTTON
// I2C SCL ------- ADC2 PB4 3| |6 PB1 AIN1 OC0B --- VOL- BUTTON
// GND 4| |5 PB0 AIN0 OC0A --- SEEK BUTTON
// +----+
//
// Compilation Settings:
// ---------------------
// Controller: ATtiny13A
// Core: MicroCore (https://github.com/MCUdude/MicroCore)
// Clockspeed: 1.2 MHz internal
// BOD: BOD disabled
// Timing: Micros disabled
//
// Leave the rest on default settings. Don't forget to "Burn bootloader"!
// No Arduino core functions or libraries are used. Use the makefile if
// you want to compile without Arduino IDE.
//
// Fuse settings: -U lfuse:w:0x2a:m -U hfuse:w:0xff:m
// ===================================================================================
// Libraries and Definitions
// ===================================================================================
// Libraries
#include <avr/io.h> // for GPIO
#include <avr/sleep.h> // for sleep functions
#include <avr/interrupt.h> // for interrupts
#include <util/delay.h> // for delays
// Pin definitions
#define BT_SEEK PB0 // CH+ button
#define BT_VOLM PB1 // VOL- button
#define BT_VOLP PB2 // VOL+ button
#define I2C_SDA PB3 // I2C serial data pin
#define I2C_SCL PB4 // I2C serial clock pin
#define BT_MASK (1<<BT_SEEK)|(1<<BT_VOLM)|(1<<BT_VOLP)
// ===================================================================================
// I2C Implementation
// ===================================================================================
// I2C macros
#define I2C_SDA_HIGH() DDRB &= ~(1<<I2C_SDA) // release SDA -> pulled HIGH by resistor
#define I2C_SDA_LOW() DDRB |= (1<<I2C_SDA) // SDA as output -> pulled LOW by MCU
#define I2C_SCL_HIGH() DDRB &= ~(1<<I2C_SCL) // release SCL -> pulled HIGH by resistor
#define I2C_SCL_LOW() DDRB |= (1<<I2C_SCL) // SCL as output -> pulled LOW by MCU
// I2C init function
void I2C_init(void) {
DDRB &= ~((1<<I2C_SDA)|(1<<I2C_SCL)); // pins as input (HIGH-Z) -> lines released
PORTB &= ~((1<<I2C_SDA)|(1<<I2C_SCL)); // should be LOW when as ouput
}
// I2C transmit one data byte to the slave, ignore ACK bit, no clock stretching allowed
void I2C_write(uint8_t data) {
for(uint8_t i = 8; i; i--, data<<=1) { // transmit 8 bits, MSB first
I2C_SDA_LOW(); // SDA LOW for now (saves some flash this way)
if(data & 0x80) I2C_SDA_HIGH(); // SDA HIGH if bit is 1
I2C_SCL_HIGH(); // clock HIGH -> slave reads the bit
I2C_SCL_LOW(); // clock LOW again
}
I2C_SDA_HIGH(); // release SDA for ACK bit of slave
I2C_SCL_HIGH(); // 9th clock pulse is for the ACK bit
I2C_SCL_LOW(); // but ACK bit is ignored
}
// I2C start transmission
void I2C_start(uint8_t addr) {
I2C_SDA_LOW(); // start condition: SDA goes LOW first
I2C_SCL_LOW(); // start condition: SCL goes LOW second
I2C_write(addr); // send slave address
}
// I2C stop transmission
void I2C_stop(void) {
I2C_SDA_LOW(); // prepare SDA for LOW to HIGH transition
I2C_SCL_HIGH(); // stop condition: SCL goes HIGH first
I2C_SDA_HIGH(); // stop condition: SDA goes HIGH second
}
// ===================================================================================
// RDA5807 Implementation
// ===================================================================================
// RDA definitions
#define RDA_ADDR_SEQ 0x20 // RDA I2C write address for sequential access
#define RDA_ADDR_INDEX 0x22 // RDA I2C write address for indexed access
#define R2_SEEK_ENABLE 0x0100 // RDA seek enable bit
#define R2_SOFT_RESET 0x0002 // RDA soft reset bit
#define R5_VOLUME 0x000F // RDA volume mask
#define RDA_VOL 5 // start volume
// RDA write registers
uint16_t RDA_regs[6] = {
0b1101001000000101, // RDA register 0x02
0b0001010111000000, // RDA register 0x03
0b0000101000000000, // RDA register 0x04
0b1000100010000000, // RDA register 0x05
0b0000000000000000, // RDA register 0x06
0b0000000000000000 // RDA register 0x07
};
// RDA write specified register
void RDA_writeReg(uint8_t reg) {
I2C_start(RDA_ADDR_INDEX); // start I2C for index write to RDA
I2C_write(0x02 + reg); // set the register to write
I2C_write(RDA_regs[reg] >> 8); // send high byte
I2C_write(RDA_regs[reg] & 0xFF); // send low byte
I2C_stop(); // stop I2C
}
// RDA write all registers
void RDA_writeAllRegs(void) {
I2C_start(RDA_ADDR_SEQ); // start I2C for sequential write to RDA
for(uint8_t i=0; i<6; i++) { // write to 6 registers
I2C_write(RDA_regs[i] >> 8); // send high byte
I2C_write(RDA_regs[i] & 0xFF); // send low byte
}
I2C_stop(); // stop I2C
}
// RDA initialize tuner
void RDA_init(void) {
I2C_init(); // init I2C
RDA_regs[0] |= R2_SOFT_RESET; // set soft reset
RDA_regs[3] |= RDA_VOL; // set start volume
RDA_writeAllRegs(); // write all registers
RDA_regs[0] &= 0xFFFD; // clear soft reset
RDA_writeReg(0); // write to register 0x02
}
// RDA set volume
void RDA_setVolume(uint8_t vol) {
RDA_regs[3] &= 0xFFF0; // clear volume bits
RDA_regs[3] |= vol; // set volume
RDA_writeReg(3); // write to register 0x05
}
// RDA seek next channel
void RDA_seekUp(void) {
RDA_regs[0] |= R2_SEEK_ENABLE; // set seek enable bit
RDA_writeReg(0); // write to register 0x02
}
// ===================================================================================
// Main Function
// ===================================================================================
int main(void) {
// Setup pins
PORTB |= (BT_MASK); // pull-ups for button pins
// Setup pin change interrupt
GIMSK = (1<<PCIE); // turn on pin change interrupts
PCMSK = (BT_MASK); // turn on interrupt on button pins
sei(); // enable global interrupts
// Disable unused peripherals and set sleep mode to save power
ADCSRA = 0; // disable ADC
ACSR = (1<<ACD); // disable analog comperator
PRR = (1<<PRTIM0) | (1<<PRADC); // shut down ADC and timer0
set_sleep_mode(SLEEP_MODE_PWR_DOWN); // set sleep mode to power down
// Setup radio
uint8_t volume = RDA_VOL; // set start volume
RDA_init(); // initialize RDA
RDA_seekUp(); // seek a channel
// Loop
while(1) {
sleep_mode(); // sleep until button is pressed
_delay_ms(1); // debounce
uint8_t buttons = ~PINB & (BT_MASK); // read button pins
switch (buttons) { // send corresponding command to RDA
case (1<<BT_SEEK): RDA_seekUp(); break;
case (1<<BT_VOLM): if(volume) RDA_setVolume(--volume); break;
case (1<<BT_VOLP): if(volume < 15) RDA_setVolume(++volume); break;
default: break;
}
}
}
// Pin change interrupt service routine
EMPTY_INTERRUPT(PCINT0_vect); // nothing to be done here, just wake up from sleep
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