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