THG TIM 2015, Техническое руководство

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TIM 2015 Technical Manual v1 (February 2018) Page 6
Chapter 1 Technical description
People can use TIM 2015 very happily without reading anything in this manual! The information in this section is provided for people who
like to look ‘under the bonnet’ (British English) or ‘under the hood’ (US English) of TIM 2015.
How TIM 2015 works
The clock is controlled by a Microchip PIC18F25K22 microcontroller running encrypted assembler code at a clock speed of 32MHz from its
internal oscillator.
Timekeeping is provided by a Maxim DS3231 RTC (Real Time Clock) chip (fitted to module MOD3 .) This chip has an integrated
temperature-compensated crystal oscillator (TCXO) and 32768 kHz crystal for timekeeping accuracy of ±2ppm (or better) from 0°C to
+40°C. A long-life CR2032 lithium 3V coin cell maintains timekeeping during power failure.
The DS3231 communicates with the microcontroller using a serial I
2
C Interface and also provides a 1-second pulse to synchronise the voice
and time display updates (module MOD3 also contains a separate memory chip, which is not used).
The time-of-day speech announcements are handled by the Catalex player module ( MOD4 ). This contains a dedicated YX5300 stereo audio
processor chip usually used for MP3 players. It also plays the WAV files used for the voice announcements in TIM 2015. The device
supports audio sampling frequencies of 8, 11.025, 12, 16, 22.05, 24, 32, 44.1 and 48 kHz.
Only one audio channel is being used for the mono recordings employed in TIM 2015. The microcontroller controls the Catalex player using
command strings sent at 9600 baud.
Voice files are stored as .WAV files (or .MP3 files) in folders on a microSD card. For each time-of-day announcement the microcontroller
compiles a list of required files and commands the Catalex module to play each file in sequence. The module reports when each file has
been played, ready for the microcontroller to request the next one.
The audio output from the Catalex player is filtered by an op-amp, IC3B (MC33072), to reduce frequencies higher than 3,300Hz, as they lie
above the range of frequencies used for telephony.