Analog Attenuation API?

[torntrousers]

Thanks for the recently committed analog functions.
Is there a problem with analog attenuation or some reason why its not exposed as an API to Arduino sketches? Or is it coming soon perhaps?

[me-no-dev]

Tried it and it did not work :)

[torntrousers]

Heh, yes me too fiddling about in esp32-hal-adc and it didn't work for me either. Could I raise this as a bug with Espressif somewhere - (I don't properly understand how all the components fit together ) - is it hardware thing or the sdk or idf ...?

[me-no-dev]

it's either hardware or we are missing some setting in the software that I do not know about. You can raise an issue in esp-idf as lower level guys visit that repo :)

[torntrousers]

Over here it was suggested to use adc1_config_channel_atten, thats seems to work ok.

Its in #include <driver/adc.h> and can do:
adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_11db);
adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_6db);
adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_2_5db);
adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_0db);

That seems to give a max input voltage of:
0db = 1.1v
2.5db = 1.4v
6db = 1.9v
11db = 3.2v

Was hoping for a little wider range.

[me-no-dev]

no wonder... I was writing to the wrong register

[me-no-dev]

please try the latest commit

    analogSetAttenuation(ADC_0db);
    analogSetPinAttenuation(A18, ADC_0db);
    analogSetPinAttenuation(A19, ADC_2_5db);
    analogSetPinAttenuation(A6, ADC_6db);
    analogSetPinAttenuation(A7, ADC_11db);