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mubase
03-19-2016, 10:14 PM
Hi all. My partner and I are starting a project that involves playing audio samples from an SD card. Quite simply, we woiuld like to know, if we want to use the audio library (which is impressive to say the least!) do we need the audio adaptor board or can we get away with using just the Teensy 3.2 board and adding our own socket for output..
?
Thanks,
Steve.S

PaulStoffregen
03-19-2016, 10:17 PM
You can play sound on the DAC pin, but it's only 12 bits and only mono. Just use the design tool to connect the dac object, instead of i2s. If using the examples, delete all the sgtl5000 stuff, since you won't have that chip.

The DAC can drive the input of amplified computer speakers, but it's not strong enough for headphones or a speaker. You need to add an amp for those.

mubase
03-20-2016, 02:15 PM
You can play sound on the DAC pin, but it's only 12 bits and only mono. Just use the design tool to connect the dac object, instead of i2s. If using the examples, delete all the sgtl5000 stuff, since you won't have that chip.

The DAC can drive the input of amplified computer speakers, but it's not strong enough for headphones or a speaker. You need to add an amp for those.

Hi Paul. Thanks for the info. Well, I've just seen your Audio board and think it'll be well worth using them instead of just the dac pin. :) I've come across the SGTL5000 before on the STm32F4 discobery and Riotboard. I've wanted to get a Teensy for audio for a couple of years now but not got round to it. The project is part of my partners's sound artist residency at Senate House Library in London (part of UCL.) We want to install speakers in the lifts there that play samples of Shakespeare lines depending upon whether the lift is ascending (angels, heaven, wings blah blah) or descending (demons, Macbeth, bowels blah blah.) We also want to install the devices along some of the corridors to be triggered as people walk past a sensor. At the moment, for the corridors we're thinking of using ultrasonics as they have a reasonable range and the sounds played could be made to increase in volume as the person walked up to it and decrease as they walk away (I know, the ears do this anyway (brainwave..lol) )but there's a dynamic involved here..or something, I'll have to ask Hannah.. Theres a stockist of the boards here in London (Cool components) which is handy. :)

PaulStoffregen
03-20-2016, 05:06 PM
The built in DAC might do pretty well for this sort of project. The main issue is going to enough speakers and a powerful amp so it can be heard at a good distance.

Ultrasonic distance sensors usually come with pretty optimistic claims about the maximum range they can detect. The work pretty well when the sound reflection is from a large & flat metal surface. Irregular and smaller shapes don't reflect the ultrasonic sound as well. Likewise for soft materials (like humans and animals) which tend to absorb much of it. You can detect the presence of people, but the range and performance will be much less than the published specs might lead you to believe.

mubase
03-20-2016, 07:38 PM
Hi Paul. OK thanks :) , well the ultrasonics will be placed in a corridor to reflect presence/movement of people. As its all concrete walls we SHOULD be OK...hmmmm...
Ahhh, also, would it be possible to use a PIR sensor to wake up the Teensy from a sleep mode? We'd like to do this as well so as to save power if we use batteries to run the devices...

mubase
03-21-2016, 12:16 PM
ooh. one more question, do we need powered speakers for the audio board or can we get away with unpowered? We only need something small for the lifts and maybe something a little louder for the corridors..

Theremingenieur
03-21-2016, 01:46 PM
The DAC output has about line level and very limited output current, thus it is not able to drive a speaker directly. But there are lots of small single-chip audio amplifiers on the market which will power your speakers with 1 to 5W depending on the needed sound pressure level.

mubase
03-21-2016, 02:22 PM
The DAC output has about line level and very limited output current, thus it is not able to drive a speaker directly. But there are lots of small single-chip audio amplifiers on the market which will power your speakers with 1 to 5W depending on the needed sound pressure level.

OK. I assume you're talking straight from the DAC pin on the Teensy board. What about if I'm using the Audio breakout board? (the one with the sgtl5000 codec on it.)

PaulStoffregen
03-21-2016, 03:03 PM
You'll need an amplifier with the audio adaptor. It only has headphone and line-level outputs.

The upcoming Prop Shield as a 2 watt audio amp. It's pretty loud when used with a decent quality 4 ohm speaker, like speakers meant for cars.

PaulStoffregen
03-21-2016, 03:15 PM
But in a large space, unless the environment is pretty quiet, 2 watts might not be enough audio power for an enjoyable experience.

Speakers and audio amps are pretty commonly available. With all audio-based installations, it's always wise to do a sound check. If the space has a lot of people or machines making background noise, do a test with the other noise present. It's amazing how loud even 1 watt sounds in a perfectly quiet room, but how inadequate it feels when you've got other noise around.

mubase
03-26-2016, 12:36 PM
Hiya. OK, we've ordered 8 of each from Hobbyelectronics in York. :)

I notice it uses a lot of the pins. If we want to use an accelerometer as well will we still be able to do that? I know with SPI you can just select a different /CE pin for each device ...

PaulStoffregen
03-29-2016, 02:11 AM
Most accelerometers use I2C, and they share nicely with SGTL5000. So even though the audio board seems to use the SDA & SCL pins, you can easily use them to also connect almost any accelerometer.

Frank B
03-29-2016, 09:03 AM
What to do with msgs like this with SPAM links ? Report them ?



Edit.. the msg i was referring to is deleted :)

defragster
03-29-2016, 09:30 AM
Odd - yeah he just copies a prior post and adds his gibberish links - I saw the gibberish but ignored because with the copied post it was 'in context'.

PaulStoffregen
03-29-2016, 01:32 PM
Ugh, yeah, that's a nasty spam technique. I just fell for it in another thread, while trying frantically to get caught up on the last few days of messages I've missed.

mubase
03-30-2016, 01:19 PM
Hi everyone. We're excited. The boards came today! :cool:
So when I've done some other stuff I'll take a look at your nice long video. :)
This is great. I've wanted to use the Teensy for a long time and now we have the opportunity!!