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https://github.com/titonbarua/micropython-ms5837-depth-sensor
Library to access MS5837 depth sensor from micropython.
https://github.com/titonbarua/micropython-ms5837-depth-sensor
depth-sensor micropython
Last synced: 22 days ago
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Library to access MS5837 depth sensor from micropython.
- Host: GitHub
- URL: https://github.com/titonbarua/micropython-ms5837-depth-sensor
- Owner: titonbarua
- License: mit
- Created: 2024-12-23T07:46:06.000Z (about 1 month ago)
- Default Branch: main
- Last Pushed: 2025-01-01T09:21:39.000Z (23 days ago)
- Last Synced: 2025-01-01T09:24:34.256Z (23 days ago)
- Topics: depth-sensor, micropython
- Language: Python
- Homepage:
- Size: 5.66 MB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Micropython Library for Reading MS5837-XXXX Pressure/Water-depth Sensors
This library implements a few micropython classes for reading data out of
popular MS5837 family pressure sensors directly into a micro-controller. These
devices are commonly found in depth sensors made by BlueRobotics.
## Features
- API-s for both blocking and asynchronous reads with asyncio.
- Configurable oversampling rates, as supported by the sensors.
- Minimal dynamic memory allocation for predictable performance.
## Supported variants
- MS5837-02BA
- MS5837-30BA
## Installation
You can install the library directly into the device using `mpremote` tool -
```bash
mpremote mip install github:titonbarua/micropython-ms5837-depth-sensor@main
```
## Example usage
### Pressure and temperature measurement
Reading data in blocking mode -
```python
import time
from machine import I2C
from ms5837.bar30 import MS5837SensorBar30
_SCL_PIN = "GP19"
_SDA_PIN = "GP18"
_OSR_RATE = 4096
# Create I2C object.
i2c_obj = I2C(1, freq=400000, sda=_SDA_PIN, scl=_SCL_PIN)
# Create and initialize sensor object.
sensor = MS5837SensorBar30(
i2c_obj,
pressure_osr=_OSR_RATE,
temperature_osr=_OSR_RATE)
while True:
pres, temp = sensor.read()
print(f"P: {pres} KPa, T: {temp} deg-C")
time.sleep(1.0)
```
### Asynchronously reading pressure and temperature
The `async_read` method can be used to read the sensor data asynchronously.
```python
import asyncio
import time
from machine import I2C
from ms5837.bar30 import MS5837SensorBar30
_SCL_PIN = "GP19"
_SDA_PIN = "GP18"
_OSR_RATE = 4096
# Create I2C object.
i2c_obj = I2C(1, freq=400000, sda=_SDA_PIN, scl=_SCL_PIN)
# Create and initialize sensor object.
sensor = MS5837SensorBar30(
i2c_obj,
pressure_osr=_OSR_RATE,
temperature_osr=_OSR_RATE)
while True:
task = sensor.async_read()
pres, temp = asyncio.run(task)
print(f"P: {pres} KPa, T: {temp} deg-C")
time.sleep(1.0)
```
The above example is silly as only a single async task is running. Ideally, you
should be having other async co-routines to utilize the time idly spent waiting
for the ADC conversion.
### Depth estimation
The `NaiveWaterDepthEstimator` class can be used with a sensor object to estimate
depth.
```python
import asyncio
import time
from machine import I2C
from ms5837.bar30 import MS5837SensorBar30
from ms5837.depth import NaiveWaterDepthEstimator
_SCL_PIN = "GP19"
_SDA_PIN = "GP18"
_OSR_RATE = 4096
_WATER_DENSITY = 1000
# Create I2C object.
i2c_obj = I2C(1, freq=400000, sda=_SDA_PIN, scl=_SCL_PIN)
# Create and initialize sensor object.
sensor = MS5837SensorBar30(
i2c_obj,
pressure_osr=_OSR_RATE,
temperature_osr=_OSR_RATE)
depth_estimator = NaiveWaterDepthEstimator(sensor, _WATER_DENSITY)
ref_pres = depth_estimator.set_ref_pressure()
print(f"Reference pressure set to: {ref_pres:.3f} KPa")
while True:
depth_m = depth_estimator.read_depth()
print("Depth: {:.2f} cm".format(depth_m * 100.0))
time.sleep(1.0)
```
`NaiveWaterDepthEstimator` also has an analogous `async_read_depth` method for
asynchronous reading.
## Running the tests
### Hardware setup
The tests were designed for an RP2040 micro-controller running micropython. Two
sensors, one MS5837-30BA and another MS5837-02BA were connected to I2C channels
1 and 0. The pin configuration is described in the beginning of
[tests/rp2040_tests.py](./tests/rp2040_tests.py) file.
### Installation
- Install the requirements with `pip install -r requirements.txt`.
- Copy the necessary files to micro-controller with command `./tools/copy_files.sh`.
### Starting a test
Benchmark blocking reads:
```bash
mpremote exec 'from rp2040_tests import *; benchmark_blocking_read(SENSOR_BAR30)'
```
Benchmark asynchronous reads:
```bash
mpremote exec 'from rp2040_tests import *; benchmark_async_read(SENSOR_BAR02)'
```
Continuously print pressure and temperature data:
```bash
mpremote exec 'from rp2040_tests import *; print_data(SENSOR_BAR30)'
```
Continuously print depth data:
```bash
mpremote exec 'from rp2040_tests import *; print_data(SENSOR_BAR02)'
```
## Benchmark results
- Micro-controller: RPi Pico 2040 running at stock speed
- Micropython version: 1.24.1
|Benchmarking setup | Depth sanity checking with a water bottle!|
|------------------------------------|-------------------------------------------|
| | |
### Timing of 100 blocking reads for MS5837-02BA
| OSR | T_avg[us]| T_stddev[us]| T_min[us]| T_max[us]| Data Rate[Hz]|
|--------|--------------|--------------|--------------|--------------|--------------|
| 256| 2516.93| 26.42| 2498.00| 2762.00| 397.31|
| 512| 3663.57| 21.20| 3644.00| 3851.00| 272.96|
| 1024| 5800.20| 17.28| 5782.00| 5945.00| 172.41|
| 2048| 10100.62| 17.86| 10083.00| 10254.00| 99.00|
| 4096| 18683.49| 17.45| 18666.00| 18832.00| 53.52|
| 8192| 35553.06| 22.05| 35518.00| 35748.00| 28.13|
### Timing of 100 async reads for MS5837-02BA
| OSR | T_avg[us]| T_stddev[us]| T_min[us]| T_max[us]| Data Rate[Hz]|
|--------|--------------|--------------|--------------|--------------|--------------|
| 256| 2489.46| 64.99| 2446.00| 3118.00| 401.69|
| 512| 5440.95| 736.74| 4586.00| 7217.00| 183.79|
| 1024| 7672.49| 1134.89| 6919.00| 11362.00| 130.34|
| 2048| 10883.84| 1508.17| 9909.00| 15514.00| 91.88|
| 4096| 18525.77| 597.80| 16941.00| 19479.00| 53.98|
| 8192| 36372.09| 561.14| 34929.00| 37511.00| 27.49|
### Timing of 100 blocking reads for MS5837-30BA
| OSR | T_avg[us]| T_stddev[us]| T_min[us]| T_max[us]| Data Rate[Hz]|
|--------|--------------|--------------|--------------|--------------|--------------|
| 256| 2606.48| 25.06| 2589.00| 2840.00| 383.66|
| 512| 3810.43| 18.49| 3792.00| 3969.00| 262.44|
| 1024| 6033.86| 21.00| 6014.00| 6217.00| 165.73|
| 2048| 10554.43| 18.85| 10536.00| 10722.00| 94.75|
| 4096| 19568.32| 23.29| 19546.00| 19784.00| 51.10|
### Timing of 100 async reads for MS5837-30BA
| OSR | T_avg[us]| T_stddev[us]| T_min[us]| T_max[us]| Data Rate[Hz]|
|--------|--------------|--------------|--------------|--------------|--------------|
| 256| 2497.80| 64.99| 2464.00| 3122.00| 400.35|
| 512| 5255.70| 718.21| 4727.00| 7278.00| 190.27|
| 1024| 7294.37| 801.82| 6923.00| 10434.00| 137.09|
| 2048| 11769.16| 1945.96| 10531.00| 19380.00| 84.97|
| 4096| 20392.47| 640.80| 18933.00| 21213.00| 49.04|
Note that effective data rate is surprisingly low for async reads with some
non-extreme OSR values. This is caused by read errors and subsequent retries. My
suspicion is on some bugs in the asyncio scheduler or sleep function.
## TYMA (Things You May Ask)
### Why not directly use the python library provided by BlueRobotics?
The library provided by BlueRobotics is not easily modifiable to use in
micropython environment, as it depends on `python-smbus` library.
### Do we really need to sample depths at high speeds?
Yes. A sensor reading is not the end, rather the beginning of a proper
estimation. High speed sampling allows one to reduce uncertainty boundary using
various techniques i.e. maximum-a-posteriori(MAP) estimation, extended Kalman
filters etc.
### Why is the depth estimation class named `NaiveWaterDepthEstimator`?
Depth estimation with the assumption that water density is constant is a naive
approach in the context of mobile robotics. The class name prefix is a caution
against forgetting the nuance. In the same spirit, the constructor forces users
to explicitly specify water density.
For a proper depth estimation, one should do an initial measurement of salinity
in the water-body. For each sensor reading, density should be estimated by
putting salinity and temperature in a model like
[TEOS-10](https://www.teos-10.org/).
A careful look at the variation of gravitational constant `g` due to location of
the experiment might also be necessary.
### Why `enable_sensor_id_check` flag is turned off by default?
Some of the 30BA variant sensors available in the market don't have their sensor
ID properly programmed in the PROM as specified by the data-sheet. I have
encountered this issue in sensors from BlueRobotics and also from raw sensors
from digikey. Others have reported the same
[issue](https://github.com/zephyrproject-rtos/zephyr/issues/60950).
## License
This software is distributed under MIT license. Look at the [LICENSE](./LICENSE)
file for the terms of distribution.
## Copyright
2025 Titon Barua