API V2 Review - DS18x20 Component #644
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tyeth
reviewed
Oct 18, 2024
tyeth
reviewed
Oct 18, 2024
tyeth
reviewed
Oct 18, 2024
tyeth
reviewed
Oct 18, 2024
tyeth
reviewed
Oct 18, 2024
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100% agree that's what I believe it does too.
The comment confused me though as it doesn't mention the division ( /16)
instead talking about a 16bit integer data type.
I only understood after visiting the getTemp2 function
…On Tue, 22 Oct 2024, 21:05 Brent Rubell, ***@***.***> wrote:
***@***.**** commented on this pull request.
------------------------------
In src/components/ds18x20/hardware.cpp
<#644 (comment)>
:
> + _drv_therm.convertTemp(_sensorId, DSTherm::MAX_CONV_TIME, false);
+
+ if (ec != OneWireNg::EC_SUCCESS)
+ return false;
+
+ // Scratchpad placeholder is static to allow reuse of the associated
+ // sensor id while reissuing readScratchpadSingle() calls.
+ // Note, due to its storage class the placeholder is zero initialized.
+ static Placeholder<DSTherm::Scratchpad> scrpd;
+ ec = _drv_therm.readScratchpad(_sensorId, scrpd);
+ if (ec != OneWireNg::EC_SUCCESS)
+ return false;
+
+ // Read the temperature from the sensor
+ long temp = scrpd->getTemp2();
+ _temp_c = temp / 16.0; // Convert from 16-bit int to float
@tyeth <https://github.com/tyeth> I could be wrong! This is why we review
each other's math.
Here's what I think this does,
- getTemp2() is the "Temperature in Celsius degrees returned as
fixed-point integer with multiplier 16"
- e.g. 20.125 C is returned as 322.
- We read temp as a long, scaled by x16
- To get the real temperature, we divide that long value by 16
- Then, we assign the value to a float, _temp_c
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I'm going to adjust the comment to reflect this conversation |
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I've cherry-picked only the commits for the DS18x20 component and selected the base as the migration branch, the file sto review should mostly reflect the DS18x20 API.
Please do not merge this branch, this is a review-only PR.
Resolves #638