Port, board and/or hardware
SEEED NRF52840,
MicroPython version
MPY: soft reboot
MicroPython v1.29.0-preview.199.ga595bbba67 on 2026-05-09; XIAO nRF52840 Sense with NRF52840
Downloaded from download page.
Reproduction
Using the SEEED XIAO NRF52840 Sense plugged into the SEEED expansion board which has:
- SSD1306 and PCF backup clock on one I2C bus
- the I2C IMU on another
from machine import Pin, I2C
def dotest():
i2c0 = I2C(0, scl=Pin("P5"), sda=Pin("P4"))
x0 = i2c0.scan()
print(f"i2c0- scl=P5 sda=P4 scan: {x0}")
i2c1b = I2C(1, scl=Pin("P27"), sda=Pin("P7"))
x1 = i2c1b.scan()
print(f"i2c1b- scl=P27 sda=P7 scan: {x1}")
dotest()
Expected behaviour
$ mpremote run test_nrfi2c.py
i2c0- scl=P5 sda=P4 scan: [51, 60, 81]
i2c1b- scl=P27 sda=P7 scan: [106]
$
Occasionally there are spurious additions to scan- that is a different, intermittent issue.
Observed behaviour
$ mpremote run test_nrfi2c.py
i2c0- scl=P5 sda=P4 scan: []
i2c1b- scl=P27 sda=P7 scan: []
$
### Additional Information
This occured with the preview updates after 20260501. It appears the major(?) change was `nrfx` updates.
Fails:
https://micropython.org/resources/firmware/SEEED_XIAO_NRF52-20260507-v1.29.0-preview.177.ge496000efc.uf2
Works:
https://micropython.org/resources/firmware/SEEED_XIAO_NRF52-20260501-v1.29.0-preview.115.g9f396bba8d.uf2
### Code of Conduct
Yes, I agree
Port, board and/or hardware
SEEED NRF52840,
MicroPython version
MPY: soft reboot
MicroPython v1.29.0-preview.199.ga595bbba67 on 2026-05-09; XIAO nRF52840 Sense with NRF52840
Downloaded from download page.
Reproduction
Using the SEEED XIAO NRF52840 Sense plugged into the SEEED expansion board which has:
Expected behaviour
Occasionally there are spurious additions to scan- that is a different, intermittent issue.
Observed behaviour