Teeny Guitar Audio Board
- Thread starter Blackaddr
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Blackaddr
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Blackaddr
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The board simply uses the SPI and SPI1 busses to connect to a a 8-SOIC SPI device. I don't see why that memory chip wouldn't work if it works on the other Teensy memory boards, though I've not tested it myself.
There are some GPIO I/O on unpopulated headers you could use for switches and encoders but it's much more effective if you control your audio effects with MIDI CC's. Properly debouncing and decoding several rotary encoders and switches reliablty (with filtering) does take some significant processor power which leaves less time for your audio effects to do their work.
It is much better to offload that type of processing to something else (a MIDI foot controller) and just have the Teensy decode the MIDI CC's which is very lightweight.
I am using THIS MIDI controller to have switches and knobs to control my Teensy audio effects. In the video I posted above, I'm using one of those with an expression pedal to send MIDI codes to the Teensy that are controlling the volume gate on my "Sound-On-Sound" effect.
You could also use the USB MIDI provided by the Teensy library to control the effects from your computer if you find a software MIDI controller you like. The Teensy should show up as a MIDI device in Windows/OSX when that feature is turned on in the Arduino IDE.
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I'm using USB MIDI too for my 3.6 synthesizer, but for guitar pedals, I prefer traditionally analog knobs on the pedal. For switches and like, I agree: deboucing is tedious. But for analog input I can't see no timing issue here. So do you think, I could use any free analog input line for that purpose?
Regarding the memory chip: it works perfectly on all teensy audio boards I used so far.
Regarding the memory chip: it works perfectly on all teensy audio boards I used so far.
Blackaddr
Well-known member
I presume you can use the A* pins? I've not used the built-in ADC on the Teensy for anything yet. If you look at the schematic, there are a couple pins (A13, A14, A15) that are available on the expansion headers or test points you could solder too. You could try using those.
Blackaddr
Well-known member
Next batch has been shipped from the assembly house. Should arrive within a week, and after final assembly and testing they'll be put into Tindie store inventory.
Tindie Store
Tindie Store
Blackaddr
Well-known member
2nd batch of boards has completed testing and have been added to the inventory at the Tindie Store.
Also, development on BAGuitar library at Github is continuing. The BAAudioEffectDelayExternal now supports both SPI RAM chips.
Also, development on BAGuitar library at Github is continuing. The BAAudioEffectDelayExternal now supports both SPI RAM chips.
Blackaddr
Well-known member
It is compatible in the sense that it uses the same pins for the codec control (I2C) and the same pins for the audio interface (I2S) as the PJRC audio board. However, you cannot stack the two of them together in order to get a headphone output.
I often use headphones for my testing/developing effects and patches, in which case I use a very small headphone amp.
I've been happy with the M-Audio Bass Traveller. It's very small (a little bigger than a matchbook), very inexpensive, and has a built in USB rechargeable battery so now power cable needed. I feed the output of my TGA Pro into it for headphones.
https://www.amazon.com/M-Audio-Bass-Traveler-Headphone-Amplifier/dp/B00X67G77O/ref=sr_1_1?ie=UTF8&qid=1513022936&sr=8-1&keywords=m-audio+headphone+amp
Blackaddr
Well-known member
The Teensy's support a second I2S interface through it's quad audio support, but you if you attempt to piggy back a PJRC audio board, you'd need to flywire the MCLK/BCLK/LRCLK pins for sure since they are not brought out to the TGA Pro user headers. I'm not sure which pins on the T3.6 are used for the second set of I2S data in/out, but you could likely flywire those as well over to the PJRC board. You would also need to get I2C control over to the audio board, which would require even more flywires. I2S + I2C + power + ground is 9 wires in total.
In a nutshell, maybe you could probably get quad audio working with both the WM8731 on the TGA pro and the SGTL5000 on the PJRC Audio board, but it would be a helluva lot simpler to just buy a headphone amp board that takes analog audio in and use that.
For example, you could use a single shielded wire to connect the TGA Pro output (solder to the output jack Tip pin on the PCB) to the analog input on this board:
http://store.digilentinc.com/pmod-amp2-audio-amplifier/
That board is mono but if you really need the stereo output I'm sure you can find a similar project board. Simply sending the analog audio output to an analog HP amp is much easier than trying to shoehorn a PJRC Audio board on the the TGA Pro. If you wanted to try to get a second I2S interface working, that board does digital as well I think if you want a challenge.
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Blackaddr
Well-known member
The existing GUI can be used and the exist modules can be used with a few caveats:
1) The AudioControlWM8731 can be used as-is, but you cannot disable the codec's HPF which introduces noise. The same problem occurs on the codec for the PJRC Audio board but Paul has provided a function to disable the noisy HPF.
- I have provided BAAudioControlWM8731 in my BAGuitar library to not only disable the noisy HPF, but also allow access to many other features on the WM8731.
2) AudioEffectExternalDelay cannot be used as-is because the CS pin for SPI is different.
- I have provided BAAudioEffectExternalDelay in my BAGuitar library to support using MEM0 and MEM1 on my board if you've ordered those options.
Otherwise, all other Audio effects should and work and so should the GUI tool
The BAGuitar library also provides some completely custom classes for easier access to the SPI memories as general purpose storage (plain old reading and writing) as well as a BAGpio class for easier use of the header pins and user LED.
I've also got more stuff planned for the BAGuitar Library in the coming months to provide more examples...
- a Sound-On-Sound effect
- new versions of Chorus and Flanger that support using external memory (to save as much on-chip RAM as possible).
- An "Analog Delay" effect that simulates the decay of analog delay pedals instead of the digitally pristine delay
Further down the road I'd like to work on...
- a Phaser effect
- a Looper
The whole goal of this platform is to get more guitar players interested in how to program effects by example.
Blackaddr
Well-known member
The codec permits them to be used simultaneously, and you can enable/control them over I2C, however they require external components (a pair of caps and a pair of resistors for L/R outputs). The datasheet specs the caps at 220uF which are quite large, it would not have been easy to fit them on the board, and then a 3.5mm output jack in addition to that. I've also taken as much care as I can to physically isolate the analog audio parts of the PCB from the digital areas, so there is even less space to work with than might appear at first.
Blackaddr
Well-known member
Not a dumb question at all! The TGA Pro board has been design to generate all the voltages it needs (3.3V digital, 3.3V analog, 12V analog) solely from the voltages that are provided by the Teensy microcontroller board itself.
The Teensy board gets it's power from the +5V USB and that's all the external power that needs to be supplied.
If you want to build a stand alone guitar pedal, the Teensy board itself can be modified to be powered by an external +5V rather than USB. Paul has instructions on PJRC.com on how to do this.
Blackaddr
Well-known member
I'll get a picture up showing the Pin 1 orientation tomorrow.
Can anyone suggest a standard enclosure? I have some 125B size (1590N1?) which are 4.77" x 2.6" x 1.39" but they seem to be a bit shallow. My teensy 3.6 has a stacked header which makes it even worse. I may try to design and print a simple lid riser this to give more headroom.
Blackaddr - Thanks so much for making the design and boards available!
Steve
Blackaddr - Thanks so much for making the design and boards available!
Steve