183 lines
4.2 KiB
Markdown
183 lines
4.2 KiB
Markdown
# bme680
|
|
|
|
Example implementation of BME680 software. The I2C/SPI drivers are meant to run on a Raspberry Pi 4.
|
|
|
|
|
|
|
|
|
|
Connecting the purple BME680 module board to SPI:
|
|
|
|
| SPI func | BME680 Pin | Raspberry Pi Pin |
|
|
| -------- | ---------- | ---------------- |
|
|
| MISO | "SDO" | GPIO 9 (Pin 21) |
|
|
| MOSI | "SDA" | GPIO 10 (Pin 19) |
|
|
| SCLK | "SCL" | GPIO 11 (Pin 23) |
|
|
| CS | "CS" | GPIO 8 (Pin 24) |
|
|
|
|
### build
|
|
```sh
|
|
$ make
|
|
```
|
|
This will create demo programs `bme680_i2c` and `bme680_spi`, and logging programs `bme680_log_i2c` and `bme680_log_spi`. They all expect the pin/devices specified in `spi.c` and `i2c.c`.
|
|
|
|
The loggers spit out the following every minute:
|
|
```
|
|
2024-08-19T18:20:00+0100 22.2358 101068 65.8092 11054.4 1
|
|
```
|
|
`Date`, `Temperature °C`, `Pressure Pa`, `% RH`, `Measured Gas resistance Ω`, `Heat stability bit`
|
|
|
|
>Note: disregard measured gas resistance if the heat stability bit is not 1.
|
|
|
|
## spi demo
|
|
```
|
|
par_t1: 26203
|
|
par_t2: 26519
|
|
par_t3: 3
|
|
par_p1: 35008
|
|
par_p2: -10284
|
|
par_p3: 88
|
|
par_p4: 9692
|
|
par_p5: -202
|
|
par_p6: 30
|
|
par_p7: 24
|
|
par_p8: -4
|
|
par_p9: -3469
|
|
par_p10: 30
|
|
par_h1: 794
|
|
par_h2: 1007
|
|
par_h3: 0
|
|
par_h4: 45
|
|
par_h5: 20
|
|
par_h6: 120
|
|
par_h7: -100
|
|
par_g1: 208
|
|
par_g2: 59781
|
|
par_g3: 18
|
|
range_switching_error: 19
|
|
res_heat_range: 1
|
|
res_heat_val: 46
|
|
float mode
|
|
tfine: 104906.162500
|
|
temp: 20.489485 degC
|
|
press: 100089.609193 Pa
|
|
humidity: 64.456540 % RH
|
|
gas resistance: 12100.310308 Ohm
|
|
== for heater target=300.0 and ambient temp=19.0 (degC)
|
|
=== gas_valid_r: 1
|
|
=== heat_stab_r: 1
|
|
```
|
|
|
|
## i2c demo
|
|
```
|
|
par_t1: 26125
|
|
par_t2: 26370
|
|
par_t3: 3
|
|
par_p1: 36262
|
|
par_p2: -10371
|
|
par_p3: 88
|
|
par_p4: 6713
|
|
par_p5: -103
|
|
par_p6: 30
|
|
par_p7: 31
|
|
par_p8: -251
|
|
par_p9: -3158
|
|
par_p10: 30
|
|
par_h1: 776
|
|
par_h2: 1010
|
|
par_h3: 0
|
|
par_h4: 45
|
|
par_h5: 20
|
|
par_h6: 120
|
|
par_h7: -100
|
|
par_g1: 183
|
|
par_g2: 59281
|
|
par_g3: 18
|
|
range_switching_error: 19
|
|
res_heat_range: 1
|
|
res_heat_val: 39
|
|
float mode
|
|
tfine: 97289.819111
|
|
temp: 19.001918 degC
|
|
press: 100226.479673 Pa
|
|
humidity: 67.022216 % RH
|
|
gas resistance: 14702.868852 Ohm
|
|
== for heater target=300.0 and ambient temp=19.0 (degC)
|
|
=== gas_valid_r: 1
|
|
=== heat_stab_r: 1
|
|
```
|
|
|
|
Note: Do not trust the gas resistance measurement if `heat_stab_r` is not `1`.
|
|
|
|
## Burn-in / logging
|
|
|
|
See file `example/log.c`
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Compile and run
|
|
```sh
|
|
stdbuf -o0 ./bme680 2>&1 | tee -a log.txt
|
|
```
|
|
|
|
This will give an output similar to this:
|
|
```
|
|
2024-05-14T13:03:02+0100 20.8916 99836.7 68.6594 7180.73 1
|
|
2024-05-14T13:04:03+0100 20.8658 99840.3 68.7844 7171.53 1
|
|
2024-05-14T13:05:03+0100 20.8979 99838.6 68.7759 7162.35 1
|
|
2024-05-14T13:06:03+0100 20.9208 99843.8 68.6436 7166.93 1
|
|
2024-05-14T13:07:03+0100 20.9303 99845.4 68.747 7144.05 1
|
|
2024-05-14T13:08:03+0100 20.9249 99846 68.7122 7139.49 0
|
|
2024-05-14T13:09:04+0100 20.9036 99845.2 68.7224 7157.76 1
|
|
2024-05-14T13:10:04+0100 20.8737 99850.5 68.575 7144.05 1
|
|
2024-05-14T13:11:04+0100 20.8753 99850.6 68.8879 7139.49 1
|
|
2024-05-14T13:12:04+0100 20.9152 99849.3 68.8602 7134.94 1
|
|
```
|
|
|
|
If last field is not 1 then the measurement, at least for gas resistance, cannot be trusted.
|
|
```sh
|
|
sed -n '/1$/p' log.txt > test.txt
|
|
```
|
|
|
|
Then graph with gnuplot
|
|
```
|
|
# gnuplot
|
|
reset
|
|
|
|
set key autotitle columnhead
|
|
set terminal pngcairo enhanced size 2*1920/3,2*1080/3
|
|
set grid
|
|
set xdata time
|
|
set timefmt "%Y-%m-%dT%H:%M:%S%z"
|
|
|
|
|
|
|
|
# gas res vs time
|
|
set title "[I_{dac}=100, 100ms, target=300 C] GasRes over time"
|
|
set xlabel "Time"
|
|
set ylabel "Gas Resistance (OHM)"
|
|
set output "gas.png"
|
|
plot 'test.txt' u 1:5 w p pt 3 ps 1 t "BME680"
|
|
|
|
|
|
set title "[I_{dac}=100, 100ms, target=300 C] Temperature over time"
|
|
set xlabel "Time"
|
|
set ylabel "Temperature (C)"
|
|
set output "temp.png"
|
|
plot 'test.txt' u 1:2 w p pt 3 ps 1 t "BME680"
|
|
|
|
set title "[I_{dac}=100, 100ms, target=300 C] Pressure over time"
|
|
set xlabel "Time"
|
|
set ylabel "Pressure (Pa)"
|
|
set output "press.png"
|
|
plot 'test.txt' u 1:3 w p pt 3 ps 1 t "BME680"
|
|
|
|
set title "[I_{dac}=100, 100ms, target=300 C] Humidity over time"
|
|
set xlabel "Time"
|
|
set ylabel "Humidity (%RH)"
|
|
set output "hum.png"
|
|
plot 'test.txt' u 1:4 w p pt 3 ps 1 t "BME680"
|
|
```
|