Use touchread pins on audio shield teensy 3.2

Status
Not open for further replies.
M

Manolo

Member
Hi, First of all thanks to the teensy community.
I am designing a .wave file player using the teensy 3.2 audio shield, the files trigger should be through the use of capacitive sensors and then using the teensy touch read pins.
In fact I used recently Bare Conductive and would like to create something analogous with teensy (but with greater audio quality). I currently have all the necessary hardware.
The biggest doubt that stopped me is what pins touch reads I can use if the audio shield deals with the pins 23,22,19,18,15 - respectively A9, A8, A5, A4, A1 ... right?
The other pins 25, 32, 33 are not usable since I have welded teensy on the shied.
The other pins 1.17.16 are the only usable ones.
At this point do I have to insert a multiplexer for use 6 capacitive sensor?

thanks
 
I dont know what you mean by teensy welded to the shield......If there is a space between the boards and it is connected as the standard layout in the datasheet it is possible to solder wires to pin 25, 32, 33 touch pads before assembly.
For the standard layout and if you only need 6 touch sensors then 16, 17, 25, 32,and 33 are available. Pin 15 is analogue in for volume pot...if you dont have a pot the pin 15 is available as touch. If you still want a pot control you can use pin 20 instead. or control the volume by software. If all this is not possible for your layout then you will have to change the config of some of the pins to use alternative pins in the library files. You will need to read the chip datasheet to get the options. but in anycase you will probably need access to some of the pads on the back of the teensy.
 
But at this point, if I used a mux mpr121 I could still get 12 pin touchsense from 1 teensy output (example pin 17)?
it's possible?
Thank you
 
You must need more than 6 touch pads so,Yes, mpr121 will give you 12 touch pins, but it talks to the host via I2C. That means 2 pins probably pins 16 and 17 as I2C not touch and if you use the new I2c_t3 wire library. Teensy3.2 already uses pins 18 and 19 for the Audio adaptor I2C control port.
 
In fact I need to use more capacitive sensors possible.
Then summarizing:
1 - I have a teensy 3.2 connected to an audio adapter board - https://www.pjrc.com/store/teensy3_audio.html and I want to use 12 capacitive sensors.
2 - I can only use the top of teensy because of the audio adapter that blocks my access to the back.
3 - To get a number of 12 touch sense inputs, you can use the mpr 121 multiplex connected to inputs 16 and 17 (scl0 and sda0), as mpr121 uses the i2c communication protocol.
4 - to use inputs 16 and 17 for the mpr121 multiplexer as touch sense I have to use the new i2c_t3 library.

all correct?
thanks
 
No, maybe not as simple as all that. I was wrong in suggesting that 16, 17. could be used as 2nd I2C port. Pins 16 & 17 are the alternative position for I2C0, default I2C0 is 18 & 19 and this is used for the audio adaptor. I2C1 is pins 29 & 30 default and 26 & 31 alternative. and 29, 30, 26, 31 are all on the back of the teensy board. These pin configs are determined by the K20 chip pin mux. I assume your adaptor board is only soldered to the teensy so why not unsolder it and get access to the back pads.
 
It is in fact the wisest thing to do is to go back and start - now I understand why in the example made by PJRC, teensy is placed under the audio shield.
Thank you Teenfor3!!, you have been very kind.
I hope to update you as soon as possible.
 
I2C is a bus so you can have several slaves and a master on the same bus. I havent tried it with teensy but should work. Teensy as master and audio adaptor as slave and your touch chip as another slave.
 
This is the adafruit product 1982 ......breakout board
The MPR121 has support for only I2C, which can be implemented with nearly any microcontroller. You can select one of 4 addresses with the ADDR pin, for a total of 48 capacitive touch pads on one I2C 2-wire bus. Using this chip is a lot easier than doing the capacitive sensing with analog inputs: it handles all the filtering for you and can be configured for more/less sensitivity.

This sensor comes as a tiny hard-to-solder chip so we put it onto a breakout board for you.
.......................................................

This is the adafruit product 1602 .......breakout board
The CAP1188 has support for both I2C and SPI, so it easy to use with any microcontroller. If you are using I2C, you can select one of 5 addresses, for a total of 40 capacitive touch pads on one I2C 2-wire bus. Using this chip is a lot easier than doing the capacitive sensing with analog inputs: it handles all the filtering for you and can be configured for more/less sensitivity.

.......................................................
 
Status
Not open for further replies.
Back
Top