RDS PIRA32 Manual
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Contents
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PIRA32 Microcontroller© 2016 Pira.cz m32.pdf - page 93.8 Output low-pass filterThe output RDS signal modulated at 57 kHz subcarrier requires no special filtering. Spurious products are keptbelow -70 dB broadcast limit and the D/A conversion residues around the sampling frequency can be cut-off usingany simple low-pass filter. This may be based either on active filter or a simple LC element. For FM broadcastpurposes the low-pass filter rejection should be at least 20 dBc on the sampling frequency. It is recommended forhigh quality FM broadcasting that the output filter characteristics interpolate at least these values:15 kHz 57 kHz 360 kHz-20 dB 0 dB -30 dB3.9 Expansion I2C busThe PIRA32 Microcontroller supports several external devices that extend its functions and features. All of thesedevices are optional, i.e. the final design is highly customizable. The devices are recognized automatically onpower-up or device reset.The I2C devices supported are listed in following table:Device name Manufacturer Description24LC256 Microchip Serial EEPROM. Non-volatile memory for storing RDS andconfiguration data. Recommended for proper function.PCF8563 NXP Battery powered backup real-time clock (RTC).MCP23008 Microchip Parallel port for 16×2 LCD display based on HD44780 driver.MCP4551-103 Microchip Digital potentiometer for software control of RDS output level.3.10 Operation without EEPROM on I2C busOperation without EEPROM is possible. If EEPROM is not detected on the I2C bus after power-up or reset, theRAM memory is filled with blank data. The RDS generator is turned off. The user may fill the RAM with validvalues using RS-232 ASCII commands and then turn on the RDS generator by the command RDSGEN=1. |
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