BreakoutLTR559(i2c) does not raise an error when LTR559 is not present

Support
1

When running the LTR559 breakout example program ( pimoroni-pico/micropython/examples/breakout_ltr559/demo.py at main · pimoroni/pimoroni-pico · GitHub ) using pico_plus2-v1.29.0-2-pimoroni-micropython.uf2 on my Pico Plus 2 W (A4 stepping), without an LTR559 attached, it reports:

Found LTR559. Part ID: 0x01

Shouldn’t it raise an error, rather than claiming to have found a non-existent LTR559?

This problem also occurs with pico_plus2_rp2350-v0.0.9-pimoroni-micropython.uf2

Later I tried it on a Plasma 2040 W running picow-55ceb1fc3e50f14c1e1ea0be73c429e0ddb3a4e0-pimoroni-micropython.uf2 ( RV3028 BreakoutRTC - Pico 2W + Breakout Garden - device not recognised - #8 by hel ), and found that also claimed an LTR559 existed when it didn’t.

In all cases it works fine when the LTR559 breakout is plugged in.

I am trying to test whether an LTR559 is present or not. I have worked around this issue by leaving a short delay after initialisation, then calling get_reading() and checking for a None response, but surely this shouldn’t be necessary…

Has anyone else seen this behaviour?

2

Yeah, looks like that old example just prints “Found LTR559” either way, which is not ideal!

Try this instead - you don’t need to specify the default I2C pins these days either, as they’re baked into the MicroPython build :)

import time
import machine
from breakout_ltr559 import BreakoutLTR559

i2c = machine.I2C()

if 0x23 in i2c.scan():
    ltr = BreakoutLTR559(i2c)

    part_id = ltr.part_id()
    print("Found LTR559. Part ID: 0x", "{:02x}".format(part_id), sep="")

    while True:
        reading = ltr.get_reading()
        if reading is not None:
            print("Lux:", reading[BreakoutLTR559.LUX], "Prox:", reading[BreakoutLTR559.PROXIMITY])

        time.sleep(0.1)

else:
    print("LTR559 not found on I2C bus. Check wiring.")
3

Thanks hel, that’s great, I’ll update my program.

And thanks for the I2C tip, I hadn’t realised that.