Bosch Sensortec sensors
BME680
The BME680 sensor from Bosch Sensortec measures relative humidity, barometric pressure, ambient temperature and gas (VOC). The open source driver provides raw measurements, such as the resistance of the gas sensing element.
The heater element of gas sensor affects the temperature and humidity measurements. Compensated temperature and humidity measurements are available trough a closed source integration library (BSEC). The BSEC provides three air quality estimates derived from raw measurements:
- index of air quality (IAQ, 0-500);
- CO2 equivalent (eCO2, ppm);
- breath VOC (bVOC), ppm).
Info
For easy of use BSEC is also provided as an Arduino library, which can be installed using the platformio library manager as follows:
pio lib install "BSEC Software Library"
The GY-MCU680v1 is a chinese module with an STM32F051K8 mirocontroller (μC) and 3.3V low-dropout regulator (LDO). The μC acts as UART bridge, providing BSEC outputs from the BME680 sensor.
The μC and sensor operate at 3.3V, but the module can be interfaced at 5V as UART pins on the STM32F051K8 are 5V tolerant. The module also breaks out the BME680 I2C pins, which are not 5V tolerant.
Protocol
Under factory settings, the serial protocol is UART 9600 8N1 3.3V/5V TTL.
Note
The alternative 115200 BAUD rate is not supported.
| Command | Description | message |
|---|---|---|
active_mode |
continuous operation | A5 56 02 FD |
passive_mode |
single-shot operation | A5 56 01 FC |
passive_read |
request last measurement | A5 56 01 FC |
sleep |
sleep mode | |
wake |
wake up from sleep mode |
Under the factory settings, the module provides 7 values packed on a 20 bit message.
The MCU680 can be further configured with the following commands:
| Description | message |
note |
|---|---|---|
| select output | A5 55 XX YY |
|
XX |= 0x01 |
temperature | |
XX |= 0x02 |
relative humidity | |
XX |= 0x04 |
atmospheric pressure | |
XX |= 0x08 |
IAQ accuracy | |
XX |= 0x10 |
gas resistance | |
XX |= 0x20 |
altitude estimate | |
YY = (0xA5 + 0x55 + XX) % 0x100 |
message checksum | |
| output all data | A5 55 3F 39 |
factory setting |
| 115200 BAUD rate | A5 58 01 FE |
not supported |
| 9600 BAUD rate | A5 58 02 FF |
factory setting |
| save settings | A5 5A 01 00 |
save current settings to flash and reset |
| reset settings | A5 5A 02 01 |
restore factory settings |
MCU680
About the MCU680 sensor (-m MCU680)
pms -m MCU680 info
Bosh Sensortec BME680 sensor observations
time measurement time [seconds since epoch]
temp temperature [°C]
rhum relative humidity [%]
pres atmospheric pressure [hPa]
IAQ_acc IAQ accuracy flag
IAQ index of air quality [0--500]
gas gas resistance [kΩ]
alt altitude estimate [m above sea level]
String formats: atm, bme (default), bsec, csv and header
Read 10 samples (-n 10), one sample every 10 seconds (-i 10)
pms -m MCU680 -n 10 -i 10 serial
2020-09-27 17:20:52: Temp. 24.3 °C, Rel.Hum. 27.6 %, Press 1012.57 hPa, 40.7 kΩ
2020-09-27 17:21:02: Temp. 24.2 °C, Rel.Hum. 27.6 %, Press 1012.53 hPa, 42.1 kΩ
2020-09-27 17:21:12: Temp. 24.2 °C, Rel.Hum. 27.6 %, Press 1012.53 hPa, 43.8 kΩ
2020-09-27 17:21:22: Temp. 24.2 °C, Rel.Hum. 27.6 %, Press 1012.55 hPa, 45.1 kΩ
2020-09-27 17:21:32: Temp. 24.2 °C, Rel.Hum. 27.6 %, Press 1012.55 hPa, 46.4 kΩ
2020-09-27 17:21:42: Temp. 24.2 °C, Rel.Hum. 27.7 %, Press 1012.51 hPa, 47.6 kΩ
2020-09-27 17:21:52: Temp. 24.1 °C, Rel.Hum. 27.7 %, Press 1012.51 hPa, 49.0 kΩ
2020-09-27 17:22:02: Temp. 24.1 °C, Rel.Hum. 27.7 %, Press 1012.51 hPa, 50.0 kΩ
2020-09-27 17:22:12: Temp. 24.1 °C, Rel.Hum. 27.7 %, Press 1012.53 hPa, 51.4 kΩ
2020-09-27 17:22:22: Temp. 24.1 °C, Rel.Hum. 27.7 %, Press 1012.51 hPa, 52.4 kΩ
Print on CSV format (-f csv)
pms -m MCU680 -n 10 -i 10 serial -f csv
time, temp, rhum, pres, IAQ_acc, IAQ, gas, alt
1601220052, 24.3, 27.6, 1012.57, 1, 25, 40.7, 5
1601220062, 24.2, 27.6, 1012.53, 1, 25, 42.1, 5
1601220072, 24.2, 27.6, 1012.53, 1, 25, 43.8, 5
1601220082, 24.2, 27.6, 1012.55, 1, 25, 45.1, 5
1601220092, 24.2, 27.6, 1012.55, 1, 25, 46.4, 5
1601220102, 24.2, 27.7, 1012.51, 1, 25, 47.6, 6
1601220112, 24.1, 27.7, 1012.51, 1, 25, 49.0, 6
1601220122, 24.1, 27.7, 1012.51, 1, 25, 50.0, 6
1601220132, 24.1, 27.7, 1012.53, 1, 25, 51.4, 5
1601220142, 24.1, 27.7, 1012.51, 1, 25, 52.4, 6
Print on hexdump format (-f hexdump)
pms -m MCU680 -n 10 -i 10 serial -f hexdump
00000000: 5a 5a 3f 0f 09 7d 0a c4 01 8b 89 00 19 00 00 9e f2 00 05 19 ZZ?..}..............
00000014: 5a 5a 3f 0f 09 79 0a c5 01 8b 85 00 19 00 00 a4 83 00 05 a9 ZZ?..y..............
00000028: 5a 5a 3f 0f 09 76 0a c8 01 8b 85 00 19 00 00 ab 32 00 05 5f ZZ?..v..........2.._
0000003c: 5a 5a 3f 0f 09 74 0a c8 01 8b 87 00 19 00 00 b0 27 00 05 59 ZZ?..t..........'..Y
00000050: 5a 5a 3f 0f 09 72 0a c9 01 8b 87 00 19 00 00 b5 33 00 05 69 ZZ?..r..........3..i
00000064: 5a 5a 3f 0f 09 70 0a d0 01 8b 83 00 19 00 00 ba 05 00 06 42 ZZ?..p.............B
00000078: 5a 5a 3f 0f 09 6f 0a d2 01 8b 83 00 19 00 00 bf 71 00 06 b4 ZZ?..o..........q...
0000008c: 5a 5a 3f 0f 09 6e 0a d0 01 8b 83 00 19 00 00 c3 6e 00 06 b2 ZZ?..n..........n...
000000a0: 5a 5a 3f 0f 09 6c 0a cf 01 8b 85 00 19 00 00 c8 ee 00 05 35 ZZ?..l.............5
000000b4: 5a 5a 3f 0f 09 6a 0a d0 01 8b 83 00 19 00 00 cc b0 00 06 f9 ZZ?..j..............