THG TIM 2015, Техническое руководство

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TIM 2015 Technical Manual v1 (February 2018) Page 35
You can add silences anywhere to the files to make them sound right. But never allow an announcement to exceed 9.8 seconds in length, as there is always a
small delay (waiting for the ‘File finished’ status notification to be received from the sound chip) after each file.
The WAV file segments in a particular voice take up around 61MB of memory. Is this acceptable or do we need to convert them to MP3 in order to save
memory?
It is perfectly acceptable and to the user, WAV files sound slightly better than MP3 files. It is perfectly acceptable to use a mixture of MP3 and WAV files
without any problem (just make sure the files are mono and the bitrate matches the rates allowed in the Catalex data sheet).
TIM 2015 is supplied with a 1GB (gigabyte) microSD card and its large capacity means there is no need to worry about file sizes. Of course TIM 2015 will also
works fine with 2GB cards. According to the Catalex specifications the player can take up to 32GB SDHC cards but we haven't tried any sizes above 2GB yet.
More Catalex considerations
The following relates to issues not mentioned in the Catalex data sheet (this document is included separately in your information pack).
They are important for making TIM 2015 behave in the way we wish it to.
1. The Catalex player is an ingenious device and priced attractively. It is not very sophisticated, however, and it cannot play more than
one file at a time. If instructed to, say, sound the three pips before a previous file has finished playing, this will cause it to
malfunction. Early versions of the data sheet for the Catalex player mentioned a ‘Serial Play’ command but when designer of TIM
2015 contacted the Catalex team, they admitted that it did not work — and removed all reference from the data sheet.
2. Did we mention, the Catalex player is not a sophisticated device? It does not know or calculate the total length of the files to be
played in a time announcement. The microcontroller simply puts all of the files in a queue and the Catalex device plays the next file
as soon as it has an indication that a file has finished playing.
At the start of the next time slot (sequence), at x8 seconds (British voices) or x0 seconds (USA voices), the microcontroller must start
a new file queue regardless of whether the Catalex player is still busy or not in order that the pips or toneburst will begin on time.
So the sequence needs to finish within about 9.8 seconds to ensure the module is not still busy when the next pips file command is
sent.
3. The 9600 baud communication link between the Catalex player and the PIC takes about 10.4ms to process each command string, so
the End of File message from the module plus the Play File command from the PIC should take only about 21ms. For some unknown