ESP32S3/S2 RISC-V ULP touch read example (IDFGH-9077)

[MacWyznawca]

Is your feature request related to a problem?

The ESP32S3 and S2 are unable to support wake-up with more than one touchpad.

Describe the solution you'd like.

However, the ULP RISC-V is able to read Touch registers and wake up the chip when any of them are touched.

An example with such a solution would be very helpful.

Describe alternatives you've considered.

No response

Additional context.

No response

[MacWyznawca]

Hi! @sudeep-mohanty! Any progress with this example? Please!!! ;-)

[sudeep-mohanty]

Hello @MacWyznawca,
Apologies for a delayed response. We have this task in our plans and will work on it asap! Apologies again for the delay.

[MacWyznawca]

Thank you @sudeep-mohanty.
This is very important for our company LuON.me, because handling touch wake-up with only one input heavily complicates the code, if we need to handle multiple touch fields.
This increases response time and decreases repeatability.
That's why we're so looking forward to an example of Touch support in ULP to speed up and stabilize battery-powered touch buttons

[sudeep-mohanty]

Hello @MacWyznawca,
Apologies once again for a delayed reply. We have started work on adding touch sensor driver support for the ULP RISC-V. In the meantime, please find attached a basic example of the touch sensor working with the ULP RISC-V core. This hasn't been tested thoroughly and is likely to have changes before it is upstreamed to GitHub but it would present the idea of how the touch peripheral would work with the ULP RISC-V core. I would encourage you to try it out and let us know your feedback on it. Thanks!
ulp_touch.zip

[MacWyznawca]

Thank you very much @sudeep-mohanty, the example works. I thought it would be more difficult (reading registers directly).
However, there is another problem. The current consumption is at a suspiciously high level. It is ~300 uA.
Our projects with ULP analog measurement and Touch Sleep enabled draw ~80-100uA in total (ESP32-S3 with other components and sensors).
Where to look for a solution?

[sudeep-mohanty]

Hi @MacWyznawca, The feature hasn't been tested thoroughly so I'm not sure why the current consumption is high. It could possibly depend on how the charge/discharge times are configured for the touch pads. The reference for this is here.

[MacWyznawca]

OK, I understand @sudeep-mohanty
For now, I'm coping by using TOUCH_FSM_MODE_SW and starting the reading before the measurement. I've managed to get down to 70-90uA (standard Touch sensor settings), because waiting for the readout also costs some energy.
If you have a better idea, I'll be glad ;-)

[leeebo]

Hi @MacWyznawca Back to the original question The ESP32S3 and S2 are unable to support wake-up with more than one touchpad. there is another solution to work around it, you can call touch_pad_config to enable the channels you want to use for deep/light sleep wakeup and call esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_ON); to enable the power for touch, then all the channels you configured can wakeup the chip

Do not call xx_sleep_channel_xx at all in this solution, and please keep in mind the more channels enabled, the more frequent the overall external charge and discharge, resulting in higher power consumption.

[MacWyznawca]

Thanks @leeebo, I have already tested this approach. Unfortunately, the use of triggering Touch timer measurements, results in power consumption of several hundred uA. Even a single measurement of 4 channels using ULP measure triggered manually 10 times per second causes a large increase in power consumption. I still have to use interpenetrating electrodes (one over the entire surface for wake-up, another in the corresponding fields is the location of touch)

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