Allow full bank reads from IO expander

[mattbue]

Hi all,

i'm using the Arduino Machine Control to capture signals from sensors on production machines and send them via USB/serial port to a PC where the data is logged. Usually only the 8 digital inputs are needed.
Since i want to get the signals every millisecond, i realized that reading the signals one by one using
digital_inputs.read(...)
takes too much time.
Instead i added methods to the ArduinoIOExpanderClass with which i can use TCA6424A::readAll(...) and TCA6424A::readBank(...).

I made some simple measurements by comparing the value comparing from micros() before and after running the "read" methods.
I also changed the I2C clock frequency.

1. Reading channel 0 to 7 one by one @100kHz: 3588 us
2. Reading channel 0 to 7 one by one @400kHz: 1337 us
3. Reading bank 0 @100kHz: 452 us
4. Reading bank 0 @400kHz: 169 us
5. Reading bank 0, 1 & 2 one by one @100kHz: 1345 us
6. Reading bank 0, 1 & 2 one by one @400kHz: 501 us
7. Reading all banks @100kHz: 653 us
8. Reading all banks @400kHz: 242 us

By running I2C at 400kHz and using the readBank(...) method I get all 8 bits of bank 0 within ~170 us which is sufficient for me.

Would it be possible to add such methods to ArduinoIOExpanderClass to have them available "out of the box"?

Best regards
matt

[pnndra]

@mattbue i would suggest you open a PR with your changes.

[manchoz]

Hi @mattbue, please, check #86

[manchoz]

Hi @per1234, I think we can close this issue: feature has been implemented and tested and there is no feedback or activity.

[per1234]

Thanks @manchoz! I'm closing this as resolved by #86