Add touch sensor support for Powered Up platform by Copilot · Pull Request #454 · pybricks/pybricks-micropython

Copilot · 2026-01-20T21:09:11Z

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

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

coveralls · 2026-01-20T21:27:18Z

coverage: 49.342% (-0.06%) from 49.4%
when pulling c31d077 on copilot/add-touch-sensor-support
into 13bad2e on master.

github-actions · 2026-01-20T21:28:15Z

Download the artifacts for this pull request:

dlech · 2026-01-20T22:14:03Z

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 · 2026-01-20T22:15:43Z

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 · 2026-01-21T09:52:35Z

pybricks/iodevices/pb_type_iodevices_pupdevice.c

-    lego_device_type_id_t type_id = LEGO_DEVICE_TYPE_ID_ANY_DC_MOTOR;
+    // Check for touch sensor first.
+    lego_device_type_id_t type_id = LEGO_DEVICE_TYPE_ID_LPF2_TOUCH;
+    pbio_error_t err = pbio_port_dcm_assert_type_id(pbio_port_dcm_init_instance(port_id - PBIO_PORT_ID_A), &type_id);


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)

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

laurensvalk · 2026-01-21T10:00:38Z

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 · 2026-01-21T15:02:07Z

@copilot fix this comment and ignore all other comments.

Copilot · 2026-01-21T15:07:09Z

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

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

esm.ubuntu.com
- Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https (dns block)

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
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

laurensvalk · 2026-01-25T18:46:20Z

I'm planning to try this out this week.

laurensvalk · 2026-01-26T08:47:29Z

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 · 2026-01-26T15:33:04Z

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.

dlech · 2026-02-01T23:01:54Z

I added the async handling.

laurensvalk · 2026-02-02T07:54:38Z

Thank you!

// REVISIT: we could probably make something more efficient here.

I've added a commit with a generic pb_type_async_return_constant. Would you like to test it?

BertLindeman · 2026-02-02T10:22:48Z

Please ignore if this is too soon to report:

While trying the old V2 syntax descriptions:
There is no error if there is no TouchSensor on the indicated port.
E.g. on an EV3 without any device attached this issues no error message:

from pybricks.hubs import EV3Brick
from pybricks.tools import wait, multitask, run_task
from pybricks.parameters import Color, Direction, Port, Stop
from pybricks.nxtdevices import Motor, TouchSensor, ColorSensor, LightSensor, UltrasonicSensor
hub = EV3Brick()

# define variables used in the doc
color = Color.GREEN  # EV3 only has RED GREEN and ORANGE
ts = TouchSensor(Port.S1)
print(f"TouchSensor is {ts}")
for x in dir(ts):
    if not x.startswith("__"):
        print("\t", x)

for i in range(5):
    print(f"ts.pressed() {ts.pressed()}")
    wait(500)

Output on firmware Pybricks MicroPython ci-release-90-v4.0.0b5 on 2026-01-30; MINDSTORMS EV3 Brick with TI Sitara AM1808
and firmware ybricks MicroPython ci-build-4686-v4.0.0b5-4-g64bc1020 on 2026-02-02; MINDSTORMS EV3 Brick with TI Sitara AM1808

TouchSensor is <TouchSensor>
         pressed
ts.pressed() False
ts.pressed() False
ts.pressed() False
ts.pressed() False
ts.pressed() False

If the sensor is attached, the output is OK.

laurensvalk · 2026-02-02T12:27:50Z

Please ignore if this is too soon to report:

Nothing is too soon, but Powered Up is also completely unrelated to NXT. Please open dedicated issues for separate things. We will lose track otherwise. If in doubt, just open it separately anyway. Closing duplicates is easier than untangling differences :)

And that is the correct behavior since not all NXT Touch Sensors are detectable, so you'd want that to pass.

BertLindeman · 2026-02-02T12:47:13Z

Thanks Laurens.
Often I am not sure...

dlech · 2026-02-02T15:57:00Z

pybricks/tools/pb_type_async.c

+        .parent_obj = ret_obj,
+        .iter_once = pb_type_async_constant_iter_once,
+        .return_map = pb_type_async_constant_return_map,
+        .state = 0,


Suggested change

.state = 0,

Technically not needed.

I'd like to make it explicit here since state isn't always zeroed in the config. In some, it is set to the protothread state at the first yield.

dlech · 2026-02-02T15:58:48Z

pybricks/tools/pb_type_async.c

+ *                               re-used, otherwise assigned newly allocated object.
+ * @returns An awaitable if the runloop is active, otherwise the constant return value.
+ */
+mp_obj_t pb_type_async_return_constant(mp_obj_t ret_obj, pb_type_async_t **prev) {


Suggested change

mp_obj_t pb_type_async_return_constant(mp_obj_t ret_obj, pb_type_async_t **prev) {

mp_obj_t pb_type_async_return_obj(mp_obj_t ret_obj, pb_type_async_t **prev) {

It doesn't need to be a constant. Any object will work.

Suggested change

mp_obj_t pb_type_async_return_constant(mp_obj_t ret_obj, pb_type_async_t **prev) {

mp_obj_t pb_type_async_return_result(mp_obj_t result_obj, pb_type_async_t **prev) {

Another alternative.

Thanks. Will update and merge tomorrow. I was thinking constant just for the name in terms of just returning the given value without any more changes or awaiting, but yes, object is a better name.

dlech · 2026-02-02T23:41:40Z

Would you like to test it?

Async usage still works.

Co-authored-by: Laurens Valk <laurens@pybricks.com>

We have a few functions with this structure: async def some_func(): if simple_case: # This commits adds a helper to do this: return some_constant return await some_awaitable_operation() Also apply this to the touch sensor value of the Powered Up device.

Copilot AI assigned Copilot and dlech Jan 20, 2026

Copilot started work on behalf of dlech January 20, 2026 21:09 View session

Copilot AI changed the title ~~[WIP] Add touch sensor support on Powered Up platform~~ Add touch sensor support for Powered Up platform Jan 20, 2026

Copilot AI requested a review from dlech January 20, 2026 21:20

Copilot finished work on behalf of dlech January 20, 2026 21:20

dlech marked this pull request as ready for review January 20, 2026 22:12

dlech requested a review from laurensvalk January 20, 2026 22:12

laurensvalk reviewed Jan 21, 2026

View reviewed changes

Copilot started work on behalf of dlech January 21, 2026 15:02 View session

Copilot finished work on behalf of dlech January 21, 2026 15:07

dlech requested a review from laurensvalk January 21, 2026 17:52

laurensvalk force-pushed the copilot/add-touch-sensor-support branch from c429735 to 628d3d2 Compare January 26, 2026 08:44

dlech force-pushed the copilot/add-touch-sensor-support branch 2 times, most recently from 20cff21 to 9cd734b Compare February 1, 2026 23:00

laurensvalk force-pushed the copilot/add-touch-sensor-support branch 3 times, most recently from 7c34485 to f51c623 Compare February 2, 2026 08:37

dlech reviewed Feb 2, 2026

View reviewed changes

dlech and others added 2 commits February 8, 2026 13:18

pbio/port_dcm_pup: Detect and use switch inputs.

b1b544a

Co-authored-by: Laurens Valk <laurens@pybricks.com>

laurensvalk force-pushed the copilot/add-touch-sensor-support branch from f51c623 to c31d077 Compare February 8, 2026 12:31

laurensvalk merged commit c31d077 into master Feb 8, 2026
34 checks passed

dlech deleted the copilot/add-touch-sensor-support branch February 8, 2026 16:23

	mp_obj_t pb_type_async_return_constant(mp_obj_t ret_obj, pb_type_async_t **prev) {
	mp_obj_t pb_type_async_return_obj(mp_obj_t ret_obj, pb_type_async_t **prev) {

	mp_obj_t pb_type_async_return_constant(mp_obj_t ret_obj, pb_type_async_t **prev) {
	mp_obj_t pb_type_async_return_result(mp_obj_t result_obj, pb_type_async_t **prev) {

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Touch Sensor Support on Powered Up Platform

Changes Completed:

Implementation Details:

Build Status:

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