80 lines
3.3 KiB

# SPDX-FileCopyrightText: 2018 Tony DiCola for Adafruit Industries
# SPDX-License-Identifier: MIT
# Simple demo of using the SI4743 RDS FM transmitter.
import time
import board
import busio
import digitalio
import adafruit_si4713
# Specify the FM frequency to transmit on in kilohertz. As the datasheet
# mentions you can only specify 50khz steps!
FREQUENCY_KHZ = 96300 # 102.300mhz
# Initialize I2C bus.
#i2c = board.I2C() # uses board.SCL and board.SDA
i2c = busio.I2C(board.SCL7, board.SDA7)
# i2c = board.STEMMA_I2C() # For using the built-in STEMMA QT connector on a microcontroller
# Initialize SI4713.
si4713 = adafruit_si4713.SI4713(i2c)
# Alternatively you can specify the I2C address of the device if it changed:
#si4713 = adafruit_si4713.SI4713(i2c, address=0x36)
# If you hooked up the reset line you should specify that too. Make sure
# to pass in a DigitalInOut instance. You will need the reset pin with the
# Raspberry Pi, and probably other devices:
si_reset = digitalio.DigitalInOut(board.D29)
print("initializing si4713 instance")
#si4713 = adafruit_si4713.SI4713(i2c, reset=si_reset, timeout_s=0.5)
# Measure the noise level for the transmit frequency (this assumes automatic
# antenna capacitance setting, but see below to adjust to a specific value).
noise = si4713.received_noise_level(FREQUENCY_KHZ)
# Alternatively measure with a specific frequency and antenna capacitance.
# This is not common but you can specify antenna capacitance as a value in pF
# from 0.25 to 47.75 (will use 0.25 steps internally). If you aren't sure
# about this value, stick with the default automatic capacitance above!
# noise = si4713.received_noise_level(FREQUENCY_KHZ, 0.25)
print("Noise at {0:0.3f} mhz: {1} dBuV".format(FREQUENCY_KHZ / 1000.0, noise))
# Tune to transmit with 115 dBuV power (max) and automatic antenna tuning
# capacitance (default, what you probably want).
si4713.tx_frequency_khz = FREQUENCY_KHZ
si4713.tx_power = 115
# Configure RDS broadcast with program ID 0xADAF (a 16-bit value you specify).
# You can also set the broadcast station name (up to 96 bytes long) and
# broadcast buffer/song information (up to 106 bytes long). Setting these is
# optional and you can later update them by setting the rds_station and
# rds_buffer property respectively. Be sure to explicitly specify station
# and buffer as byte strings so the character encoding is clear.
si4713.configure_rds(0xADAF, station=b"AdaRadio", rds_buffer=b"Adafruit g0th Radio!")
# Print out some transmitter state:
print("Transmitting at {0:0.3f} mhz".format(si4713.tx_frequency_khz / 1000.0))
print("Transmitter power: {0} dBuV".format(si4713.tx_power))
"Transmitter antenna capacitance: {0:0.2} pF".format(si4713.tx_antenna_capacitance)
# Set GPIO1 and GPIO2 to actively driven outputs.
si4713.gpio_control(gpio1=True, gpio2=True)
# Main loop will print input audio level and state and blink the GPIOs.
while True:
# Print input audio level and state.
print("Input level: {0} dBfs".format(si4713.input_level))
print("ASQ status: 0x{0:02x}".format(si4713.audio_signal_status))
# 'Blink' GPIO1 and GPIO2 alternatively on and off.
si4713.gpio_set(gpio1=True, gpio2=False) # GPIO1 high, GPIO2 low
si4713.gpio_set(gpio1=False, gpio2=True) # GPIO1 low, GPIO2 high