Add touch sensor support for Powered Up platform

[Copilot]

Touch Sensor Support on Powered Up Platform

Changes Completed:

• Add sensor_data field to struct _pbio_port_dcm_t in lib/pbio/src/port_dcm_pup.c
• Uncomment line in pbio_port_dcm_thread() to read touch sensor value and store it
• Update pbio_port_dcm_get_analog_value() to return dcm->sensor_data
• Update pbio_port_dcm_assert_type_id() to handle touch sensor type
• Add touch sensor handling in Python bindings in pybricks/iodevices/pb_type_iodevices_pupdevice.c
• Build and test the changes with make -C bricks/technichub
• Address code review feedback - use proper API abstraction

Implementation Details:

C Library Changes (lib/pbio/src/port_dcm_pup.c):

• Added uint32_t sensor_data field to struct _pbio_port_dcm_t to store touch sensor readings
• Modified pbio_port_dcm_thread() to read touch sensor value from GPIO pin p5 and store it in dcm->sensor_data
• Updated pbio_port_dcm_get_analog_value() to return the stored sensor_data value
• Added LEGO_DEVICE_TYPE_ID_LPF2_TOUCH case to pbio_port_dcm_assert_type_id() to properly detect touch sensors

Python Bindings (pybricks/iodevices/pb_type_iodevices_pupdevice.c):

• Added passive_port field to iodevices_PUPDevice_obj_t to store port reference for passive devices
• Updated init_passive_pup_device() to check for touch sensor using pbio_port_get_analog_value() (proper abstraction)
• Modified iodevices_PUPDevice_read() to handle touch sensor reads by calling pbio_port_get_analog_value()
• Touch sensor read returns a boolean value indicating pressed state

Build Status:

✅ Successfully builds for technichub platform

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Touch sensor support on Powered Up platform</issue_title>
<issue_description>There are not any official LEGO touch sensors for Powered Up. However, from reverse engineering, we have seen that it was at least considered at some point. We can take advantage of this to allow people to make their own 3rd-party touch sensor.

Here is how we could do it:

The easy parts are that we need read data from the sensor. We just need to uncomment the last line here (from lib/pbio/src/port_dcm_pup.c):

            // ID1 is inverse of touch sensor value
            // TODO: save this value to sensor dcm
            // sensor_data = !pbdrv_gpio_input(&pins->p5);

And we need a way to get the data in Python which can be done with the following change:

diff --git a/pybricks/iodevices/pb_type_iodevices_pupdevice.c b/pybricks/iodevices/pb_type_iodevices_pupdevice.c
index f0da7c452..bb114b9a1 100644
--- a/pybricks/iodevices/pb_type_iodevices_pupdevice.c
+++ b/pybricks/iodevices/pb_type_iodevices_pupdevice.c
@@ -164,6 +164,11 @@ static mp_obj_t iodevices_PUPDevice_read(size_t n_args, const mp_obj_t *pos_args
         iodevices_PUPDevice_obj_t, self,
         PB_ARG_REQUIRED(mode));
 
+    if (self->passive_id == LEGO_DEVICE_TYPE_ID_LPF2_TOUCH) {
+        // TODO: replace `sensor_data` with actual reading from the touch sensor
+        return mp_obj_new_bool(sensor_data);
+    }
+
     // Passive devices don't support reading.
     if (self->passive_id != LEGO_DEVICE_TYPE_ID_LPF2_UNKNOWN_UART) {
         pb_assert(PBIO_ERROR_INVALID_OP);

The tricky part is that sensor_data is not defined and we need to figure out the correct way to pass data from one module to the other.

For example, we could add a uint32_t sensor_data; field to

struct _pbio_port_dcm_t {
    /** Most recent one-off device ID candidate. */
    lego_device_type_id_t type_id;
    /** Previous one-off device ID candidate. */
    lego_device_type_id_t prev_type_id;
    /** Number of consecutive detections of the same device ID. */
    uint8_t dev_id_match_count;
    // Intermediate state values to preserve in between async calls.
    dev_id_group_t dev_id1_group;
    uint8_t gpio_value;
    uint8_t prev_gpio_value;
};

Then modify this function to return dcm->sensor_data;.

uint32_t pbio_port_dcm_get_analog_value(pbio_port_dcm_t *dcm, const pbdrv_ioport_pins_t *pins, bool active) {
    return 0;
}

And in iodevices_PUPDevice_read() replace sensor_data with a call to pbio_port_get_analog_value() to get that value.

Originally posted by @dlech in pybricks/support#2556 (reply in thread)</issue_description>

<agent_instructions>Use the information in the issue to make the required code changes. The code should compile with make -C bricks/technichub.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Touch sensor support on Powered Up platform support#2558

---

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[coveralls]

coverage: 49.86%. remained the same
when pulling 628d3d2 on copilot/add-touch-sensor-support
into 3874930 on master.

[github-actions]

Download the artifacts for this pull request:

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• technichub-firmware-build-4637-git4e712682.zip
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• primehub-firmware-build-4637-git4e712682.zip
• buildhat-firmware-build-4637-git4e712682.zip

[dlech]

Wow, it actually worked on the first try!

from pybricks.iodevices import PUPDevice
from pybricks.parameters import Port
from pybricks.tools import wait

device = PUPDevice(Port.B)

# Should print 5 for touch sensor
print(device.info())

while True:
    # prints True when pressed, otherwise False
    print(device.read(0))
    wait(500)

{'id': 5}
False
...
False
True
False
False
True
True
True
True
False
True
True
True
True
False
...

[dlech]

Required wiring:

• Connect smaller resistor (e.g >= 220 Ω) between pin 5 (ID1) and pin 6 (ID2) for proper ID detection.
• Connect bigger resistor (e.g. 10kΩ) in series with touch sensor between pins 5 (ID1) and 3 (GND).

[laurensvalk]

Ew 😄

Could assert getting an analog value, which will assert the type without resetting the dcm.

pbio_port_get_analog_value(pbio_port_t *port, lego_device_type_id_t type_id, bool active, uint32_t *value)

[Copilot]

Fixed in c429735. Now using pbio_port_get_analog_value() instead of directly accessing the dcm.

[laurensvalk]

Impressive! Heh, I guess we have fairly good abstractions. 🙈

I've been wondering if we should have an iodevices.GPIODevice on all platforms, but I suppose an auto-detectable LPF2 sensor is nice. read(0) does ignore the 0 here so it is a little out of place, but then again so is the dc motor stuff on this class.

[dlech]

@copilot fix this comment and ignore all other comments.

[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

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• esm.ubuntu.com
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If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
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[laurensvalk]

I'm planning to try this out this week.

[laurensvalk]

Fixed a few more cleanups and mistakes.

Another caveat that would have introduced a subtle bug is that reading passive devices does not return an awaitable in async mode. I'm kind of inclined to leave it that way and add a comment instead. I don't think this feature will be used much.

[dlech]

I'm kind of inclined to leave it that way and add a comment instead. I don't think this feature will be used much.

Wouldn't that break using it with block coding?

Do we have a wait_or_await function that doesn't require a coroutine? It seems like this would be useful and similar to Python when an async def doesn't contain any await.