Bare Bones Radio Code Snippets.

In main, define the following:

//set to KRKT Albany at 99.9Mhz initially
volatile uint16_t  current_fm_freq =  9990; //0x2706, arg2, arg3; 99.9Mhz, 200khz steps
extern uint8_t  si4734_wr_buf[9];
extern uint8_t  si4734_rd_buf[9];
extern uint8_t  si4734_tune_status_buf[8];
extern volatile uint8_t STC_interrupt;     //indicates tune or seek is done


You will also need this:
//******************************************************************************
//                          External Interrupt 7 ISR                     
// Handles the interrupts from the radio that tells us when a command is done.
// The interrupt can come from either a "clear to send" (CTS) following most
// commands or a "seek tune complete" interrupt (STC) when a scan or tune command
// like fm_tune_freq is issued. The GPIO2/INT pin on the Si4734 emits a low
// pulse to indicate the interrupt. I have measured but the datasheet does not
// confirm a width of 3uS for CTS and 1.5uS for STC interrupts.
//
// I am presently using the Si4734 so that its only interrupting when the 
// scan_tune_complete is pulsing. Seems to work fine. (12.2014)
//
// External interrupt 7 is on Port E bit 7. The interrupt is triggered on the
// rising edge of Port E bit 7.  The i/o clock must be running to detect the
// edge (not asynchronouslly triggered)
//******************************************************************************
ISR(INT7_vect){STC_interrupt = TRUE;}
//******************************************************************************


Port E inital values and setup.  This may be different from yours for bits 0,1,6.

//                           DDRE:  0 0 0 0 1 0 1 1
//   (^ edge int from radio) bit 7--| | | | | | | |--bit 0 USART0 RX
//(shift/load_n for 74HC165) bit 6----| | | | | |----bit 1 USART0 TX
//                           bit 5------| | | |------bit 2 (radio reset, active high)
//                  (unused) bit 4--------| |--------bit 3 (TCNT3 PWM output for volume control)

DDRE  |= 0x04; //Port E bit 2 is active high reset for radio 
DDRE  |= 0x40; //Port E bit 6 is shift/load_n for encoder 74HC165
DDRE  |= 0x08; //Port E bit 3 is TCNT3 PWM output for volume
PORTE |= 0x04; //radio reset is on at powerup (active high)
PORTE |= 0x40; //pulse low to load switch values, else its in shift mode


Given the hardware setup reflected above, here is the radio reset sequence.
//hardware reset of Si4734
PORTE &= ~(1<<PE7); //int2 initially low to sense TWI mode
DDRE  |= 0x80;      //turn on Port E bit 7 to drive it low
PORTE |=  (1<<PE2); //hardware reset Si4734 
_delay_us(200);     //hold for 200us, 100us by spec         
PORTE &= ~(1<<PE2); //release reset 
_delay_us(30);      //5us required because of my slow I2C translators I suspect
                    //Si code in "low" has 30us delay...no explaination given
DDRE  &= ~(0x80);   //now Port E bit 7 becomes input from the radio interrupt


Once its setup, you can set the station and get the received signal strength.

fm_pwr_up();        //power up radio
while(twi_busy()){} //spin while TWI is busy 
fm_tune_freq();     //tune to frequency      

//retrive the receive strength and display on the bargraph display
while(twi_busy()){}                //spin while TWI is busy 
fm_rsq_status();                   //get status of radio tuning operation
rssi =  si4734_tune_status_buf[4]; //get tune status 
//redefine rssi to be a thermometer code
  if(rssi<= 8) {rssi = 0x00;} else
  if(rssi<=16) {rssi = 0x01;} else
  if(rssi<=24) {rssi = 0x03;} else
  if(rssi<=32) {rssi = 0x07;} else
  if(rssi<=40) {rssi = 0x0F;} else
  if(rssi<=48) {rssi = 0x1F;} else
  if(rssi<=56) {rssi = 0x3F;} else
  if(rssi<=64) {rssi = 0x7F;} else
  if(rssi>=64) {rssi = 0xFF;}