rwaldron/johnny-five

BMP180 Temperature (and consequently Pressure) Error ( > about 40 °C )

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#1696 opened on Aug 7, 2020

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 (2 comments) (0 reactions) (0 assignees)JavaScript (13,152 stars) (1,845 forks)batch import
BugClass:BarometerGood First IssueHardware Required

Description

The uncompensated temperature of the BMP180 is incorrectly converted to a 16-bit signed value, instead of a 32-bit signed value (long). Since the data is 16-bits wide and can therefore not be negative, the easy fix would be to do the following:

sip.js(1128): uncompensated = uint16(data[0], data[1]);

Please see page 15 of the manual of the BMP180 chip: https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BMP180-DS000.pdf

Contributor guide

Tech stack
javascriptnodejs
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
90
Research direction
The issue identifies a bug in the BMP180 driver where uncompensated temperature is incorrectly converted to a 16 bit signed value instead of a 32 bit signed value. The suggested fix is to modify line 1128 of sip.js to use uint16() to read the raw data, then cast to a signed 32 bit integer. Review the BMP180 datasheet section on temperature measurement to confirm the correct data type. After making the change, test with temperatures above 40°C to ensure pressure readings are also corrected.