MPPT 2420 LC "No battery temp sensor" detection does not work anymore on v21.0

[hogthrob]

The calculated "open sensor" temperature on the MPP 2420 LC is around -32.5 and not below -50 as required for

charge-controller-firmware/app/src/daq.cpp

Line 251 in a56b0d0

if (bat_temp > -50) {

to do its magic. Was working with old firmware from 2019. Could not see the difference in the code easily, looks to me more or less identical, hence raising the issue here. I personally solved the problem by entirely disabling the sensor via an mppt_2420_lc.overlay file in the app directory:

/*
 * Copyright (c) The Libre Solar Project Contributors
 *
 * SPDX-License-Identifier: Apache-2.0
 */

/ {
        pcb {
                version-str = "v0.10";
                version-num = <10>;
        };

        adc-inputs {
                // /delete-node/ temp-bat;
        };
};

but it would be nicer, if we get back the original automatic detection capability.

[martinjaeger]

That's interesting. Previously I got values below -70°C IIRC, so I thought the -50 setting would be pretty safe. I'll double-check if the Zephyr pinctrl driver set some pull-ups or pull-downs automatically, which would be an explanation for the changed behavior.

[hogthrob]

Just for the record: I tried to put a 10k resistor on the NTC connections and it does show exactly the expected 25°C on the display.