TIM 2015 Technical Manual v1 (February 2018)
Page 36
reason the Catalex module sometimes repeats the End of File message. If that happens, the PIC just ignores it but it appears that the
Catalex module then delays playout of the next file.
4.
The most significant delay that you need to consider relates to the amount of time required by the Catalex module to access each file
stored on the microSD card. To confuse things further, this delay varies according to the card speed, the formatting option chosen
and the degree of fragmentation. The delay could in theory be reduced a little by changing the SD card format settings (increasing the
allocation unit size) — but not enough to make this ploy worthwhile.
5.
Another thing that can delay playback slightly is the microSD card formatting cluster size. The designer of this project experimented
with increasing the cluster size from the default and it did reduce the time taken to load a file from the SD card (but this was a matter
of milliseconds, so it should not really make much difference unless the sequence timing is very close to being too long).
6.
The Catalex module begins to fade-up at around 60ms after the start of each file. If your audio files begin immediately (with no
preliminary silence), this leads to some loss of sound.
Consequently you need to include at least 60ms of silence at the beginning of
your audio file
. This simple to arrange in Audacity.
7.
As a result of all these factors the program starts the command for the pips file 98ms earlier than second x8 (or second x0 for USA-
format voices) to allow the pips to start playing promptly at second x8 (or x0).
8.
Fragmentation of the data on the microSD card caused by files being added and removed can cause the Catalex module to fail to play
files (delete all files on the card and re-copy all files in one fell swoop to avoid this problem). The other delays (the time taken to
execute serial commands and latency in accessing data on the microSD card) may also contribute to the sequence over-running into
the next pips and the Catalex player becoming confused and truncating announcements. We suspect that the Catalex file processing
system is very basic and does not handle fragmented files very well.
9.
The Catalex device will definitely truncate (cut off) the end of a file being played if it receives the next Play File command too early
(for example it always sends the Play File command for the three pips at the start of second 8 regardless of any existing file still
playing). For this reason the ‘and
nn
seconds’ audio file may need to be shortened (by removing some silence following the speech)
to give the microcontroller more time to ensure the Catalex module has finished before sending the command to play the three pips
.
Careful editing of voice files (and not putting more than five voices in a microSD card will avoid these unwanted effects.
10.
MP3 files do not work well with TIM 2015. While using some MP3 files, the designer encountered trouble with files not playing
properly. But they worked fine after converting them to .WAV format and also removing any data from the file headers (created when
saving them in Audacity).
Содержание TIM 2015
Страница 1: ...TIM 2015 Technical Manual v1 February 2018 Page 1 TIM 2015 Speaking Clock TECHNICAL MANUAL...
Страница 9: ...TIM 2015 Technical Manual v1 February 2018 Page 9 Board dimensions 140 x 85mm...
Страница 10: ...TIM 2015 Technical Manual v1 February 2018 Page 10 Board layout...
Страница 11: ...TIM 2015 Technical Manual v1 February 2018 Page 11 Circuit diagram...