What is a good Microcontroller with native capacitive touch sensing?

Thread Starter

Arjuna_1000

Joined May 6, 2021
10
Project Description

I am working on a project that requires a large grid of capacitive touch sensors, around 72 of them. It is a kind of guitar fretboard that would then send MIDI information to a computer.

Requirements

- 72 touchpoints
- Least latency possible (since it is an audio project)

Current Prototype

I am currently using a Teensy 3.6 which has hardware based capacitive touch sensing: see here. It works very well. I am using 2 "Touch Pins" and then 2 analog multiplexers so I am currently reading around 30 different capacitive touch points.

Problem

I am thinking about going from prototype to a more production kind of product but I'm not sure which microcontroller would make more sense to use.

Options:

Teensy 3.6 (current prototype)

Pros

- I tried it and it works

Cons
- Expensive
- Overkill for my needs?
- I need a teensy board, or how can I program the chip on my own?
- Any pointers as to how would I go about getting capacitive touch sensing from that same MCU?

ESP32

Pros

- It comes with hardware based touch capacitance in 10 pins.
- I read it has a poor DAC resolution, but this might be irrelevant for my purposes?

STM32

Cons

- I found there is an STM32 library for capacitive touch sensing with support only for some of their MCUs, but couldn't find any example on the internet where it is being implemented.
- I read in an stm32 forum someone warning about the complexity of implementing reliably capacitive touch sensing

Pros
- It supports simultaneous channel acquisition

External Capacitive Touch Sensor: Like this one

Pros
- Many choices of MCU with I2C or SPI would work out for this one
- It is a single purpose chip should it should do its job just fine
- You can get up to 64 channels for a single IC like this one

Cons
- Will it be significantly slower than in-board touch sensing?
 

drjohsmith

Joined Dec 13, 2021
458
Project Description

I am working on a project that requires a large grid of capacitive touch sensors, around 72 of them. It is a kind of guitar fretboard that would then send MIDI information to a computer.

Requirements

- 72 touchpoints
- Least latency possible (since it is an audio project)

Current Prototype

I am currently using a Teensy 3.6 which has hardware based capacitive touch sensing: see here. It works very well. I am using 2 "Touch Pins" and then 2 analog multiplexers so I am currently reading around 30 different capacitive touch points.

Problem

I am thinking about going from prototype to a more production kind of product but I'm not sure which microcontroller would make more sense to use.

Options:

Teensy 3.6 (current prototype)

Pros

- I tried it and it works

Cons
- Expensive
- Overkill for my needs?
- I need a teensy board, or how can I program the chip on my own?
- Any pointers as to how would I go about getting capacitive touch sensing from that same MCU?

ESP32

Pros

- It comes with hardware based touch capacitance in 10 pins.
- I read it has a poor DAC resolution, but this might be irrelevant for my purposes?

STM32

Cons

- I found there is an STM32 library for capacitive touch sensing with support only for some of their MCUs, but couldn't find any example on the internet where it is being implemented.
- I read in an stm32 forum someone warning about the complexity of implementing reliably capacitive touch sensing

Pros
- It supports simultaneous channel acquisition

External Capacitive Touch Sensor: Like this one

Pros
- Many choices of MCU with I2C or SPI would work out for this one
- It is a single purpose chip should it should do its job just fine
- You can get up to 64 channels for a single IC like this one

Cons
- Will it be significantly slower than in-board touch sensing?
I would suggest that in the current environment,
you would have to purchase a big pile of parts to get cheaper than a Teensey 3
 
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