Temp/Barometer

[johnmark]

My project team and I are having a hard time getting the BMP280 to return temperature and pressure data. (We really just want altitude). We are using the script from ozzmaker.com, found here:

https://github.com/ozzmaker/BerryIMU/tree/master/python-BMP280-temperature-pressure

When we run the script as-is, the following Error is returned

 

File ‘bmp280.py”, line 85, in <module>

p= (p – (var2/4096.0)) * 6250.0 /var1

ZeroDivisionError: float division by zero

 

Digging through the file, we have traced back var1 to the read from the temperature sensor, which is reading 0.

We have also done due diligence with the hardware, and the connections are securely connected. Additionally, the GPS and IMU functions are working correctly.

 

P.S. I apologize that this will be my second post in a couple days, we’ve been spending a lot of time hitting our heads against a wall with this module. We bought this module hoping for a one-stop-shop off-the-shelf solution to make it easy to dump GPS and 10DoF data into a CSV file but have found that integrating all the different scripts has been a lot more work than anticipated. Any help/direction to a script which maybe already does this would be greatly appreciated.

[johnmark]

Edit: Confirmed, the data returned from the command bus.read_i2c_block_data(0x77, 0x88, 24) is all zeros.

b1 = bus.read_i2c_block_data(0x77, 0x88, 24)
print(b1)
> 0,0,0,0,0,0,0

[PeterP]

Can you check on the back of the PCB and see what version you have?  if you have version 3.5, then it would be using the BMP388.  Sorry for any confusion.

 

Try the attached code.

 

Peter --OzzMaker.com --

[johnmark]

Just looked on the back of the berryGPS-IMU board, and confirmed that it is, in fact, version 3.5.

I do not see any code attached to your previous message? Could you resend link?

[PeterP]

#!/usr/bin/python
# -*- coding: utf-8 -*-
import time
import smbus
import math
# define BMP388 Device I2C address
I2C_ADD_BMP388_AD0_LOW = 0x76
I2C_ADD_BMP388_AD0_HIGH = 0x77
I2C_ADD_BMP388 = I2C_ADD_BMP388_AD0_HIGH
BMP388_REG_ADD_WIA = 0x00
BMP388_REG_VAL_WIA = 0x50
BMP388_REG_ADD_ERR = 0x02
BMP388_REG_VAL_FATAL_ERR = 0x01
BMP388_REG_VAL_CMD_ERR = 0x02
BMP388_REG_VAL_CONF_ERR = 0x04
BMP388_REG_ADD_STATUS = 0x03
BMP388_REG_VAL_CMD_RDY = 0x10
BMP388_REG_VAL_DRDY_PRESS = 0x20
BMP388_REG_VAL_DRDY_TEMP = 0x40
BMP388_REG_ADD_CMD = 0x7E
BMP388_REG_VAL_EXTMODE_EN = 0x34
BMP388_REG_VAL_FIFI_FLUSH = 0xB0
BMP388_REG_VAL_SOFT_RESET = 0xB6
BMP388_REG_ADD_PWR_CTRL = 0x1B
BMP388_REG_VAL_PRESS_EN = 0x01
BMP388_REG_VAL_TEMP_EN = 0x02
BMP388_REG_VAL_NORMAL_MODE = 0x30
BMP388_REG_ADD_PRESS_XLSB = 0x04
BMP388_REG_ADD_PRESS_LSB = 0x05
BMP388_REG_ADD_PRESS_MSB = 0x06
BMP388_REG_ADD_TEMP_XLSB = 0x07
BMP388_REG_ADD_TEMP_LSB = 0x08
BMP388_REG_ADD_TEMP_MSB = 0x09
BMP388_REG_ADD_T1_LSB = 0x31
BMP388_REG_ADD_T1_MSB = 0x32
BMP388_REG_ADD_T2_LSB = 0x33
BMP388_REG_ADD_T2_MSB = 0x34
BMP388_REG_ADD_T3 = 0x35
BMP388_REG_ADD_P1_LSB = 0x36
BMP388_REG_ADD_P1_MSB = 0x37
BMP388_REG_ADD_P2_LSB = 0x38
BMP388_REG_ADD_P2_MSB = 0x39
BMP388_REG_ADD_P3 = 0x3A
BMP388_REG_ADD_P4 = 0x3B
BMP388_REG_ADD_P5_LSB = 0x3C
BMP388_REG_ADD_P5_MSB = 0x3D
BMP388_REG_ADD_P6_LSB = 0x3E
BMP388_REG_ADD_P6_MSB = 0x3F
BMP388_REG_ADD_P7 = 0x40
BMP388_REG_ADD_P8 = 0x41
BMP388_REG_ADD_P9_LSB = 0x42
BMP388_REG_ADD_P9_MSB = 0x43
BMP388_REG_ADD_P10 = 0x44
BMP388_REG_ADD_P11 = 0x45
class BMP388(object):
    """docstring for BMP388"""
    def __init__(self, address=I2C_ADD_BMP388):
        self._address = address
        self._bus = smbus.SMBus(0x01)
        # Load calibration values.
        if self._read_byte(BMP388_REG_ADD_WIA) == BMP388_REG_VAL_WIA:
            print("Pressure sersor is BMP388!\r\n")
            u8RegData = self._read_byte(BMP388_REG_ADD_STATUS)
            if u8RegData & BMP388_REG_VAL_CMD_RDY:
                self._write_byte(BMP388_REG_ADD_CMD,
                                 BMP388_REG_VAL_SOFT_RESET)
                time.sleep(0.01)
        else:
            print ("Pressure sersor NULL!\r\n")
        self._write_byte(BMP388_REG_ADD_PWR_CTRL,
                         BMP388_REG_VAL_PRESS_EN
                         | BMP388_REG_VAL_TEMP_EN
                         | BMP388_REG_VAL_NORMAL_MODE)
        self._load_calibration()
    def _read_byte(self, cmd):
        return self._bus.read_byte_data(self._address, cmd)
    def _read_s8(self, cmd):
        result = self._read_byte(cmd)
        if result > 128:
            result -= 256
        return result
    def _read_u16(self, cmd):
        LSB = self._bus.read_byte_data(self._address, cmd)
        MSB = self._bus.read_byte_data(self._address, cmd + 0x01)
        return (MSB << 0x08) + LSB
    def _read_s16(self, cmd):
        result = self._read_u16(cmd)
        if result > 32767:
            result -= 65536
        return result
    def _write_byte(self, cmd, val):
        self._bus.write_byte_data(self._address, cmd, val)
    def _load_calibration(self):
        print ("_load_calibration\r\n")
        self.T1 = self._read_u16(BMP388_REG_ADD_T1_LSB)
        self.T2 = self._read_u16(BMP388_REG_ADD_T2_LSB)
        self.T3 = self._read_s8(BMP388_REG_ADD_T3)
        self.P1 = self._read_s16(BMP388_REG_ADD_P1_LSB)
        self.P2 = self._read_s16(BMP388_REG_ADD_P2_LSB)
        self.P3 = self._read_s8(BMP388_REG_ADD_P3)
        self.P4 = self._read_s8(BMP388_REG_ADD_P4)
        self.P5 = self._read_u16(BMP388_REG_ADD_P5_LSB)
        self.P6 = self._read_u16(BMP388_REG_ADD_P6_LSB)
        self.P7 = self._read_s8(BMP388_REG_ADD_P7)
        self.P8 = self._read_s8(BMP388_REG_ADD_P8)
        self.P9 = self._read_s16(BMP388_REG_ADD_P9_LSB)
        self.P10 = self._read_s8(BMP388_REG_ADD_P10)
        self.P11 = self._read_s8(BMP388_REG_ADD_P11)
        # print(self.T1)
        # print(self.T2)
        # print(self.T3)
        # print(self.P1)
        # print(self.P2)
        # print(self.P3)
        # print(self.P4)
        # print(self.P5)
        # print(self.P6)
        # print(self.P7)
        # print(self.P8)
        # print(self.P9)
        # print(self.P10)
        # print(self.P11)
    def compensate_temperature(self, adc_T):
        partial_data1 = adc_T - 256 * self.T1
        partial_data2 = self.T2 * partial_data1
        partial_data3 = partial_data1 * partial_data1
        partial_data4 = partial_data3 * self.T3
        partial_data5 = partial_data2 * 262144 + partial_data4
        partial_data6 = partial_data5 / 4294967296
        self.T_fine = partial_data6
        comp_temp = partial_data6 * 25 / 16384
        return comp_temp
    def compensate_pressure(self, adc_P):
        partial_data1 = self.T_fine * self.T_fine
        partial_data2 = partial_data1 / 0x40
        partial_data3 = partial_data2 * self.T_fine / 256
        partial_data4 = self.P8 * partial_data3 / 0x20
        partial_data5 = self.P7 * partial_data1 * 0x10
        partial_data6 = self.P6 * self.T_fine * 4194304
        offset = self.P5 * 140737488355328 + partial_data4 \
            + partial_data5 + partial_data6
        partial_data2 = self.P4 * partial_data3 / 0x20
        partial_data4 = self.P3 * partial_data1 * 0x04
        partial_data5 = (self.P2 - 16384) * self.T_fine * 2097152
        sensitivity = (self.P1 - 16384) * 70368744177664 \
            + partial_data2 + partial_data4 + partial_data5
        partial_data1 = sensitivity / 16777216 * adc_P
        partial_data2 = self.P10 * self.T_fine
        partial_data3 = partial_data2 + 65536 * self.P9
        partial_data4 = partial_data3 * adc_P / 8192
        partial_data5 = partial_data4 * adc_P / 512
        partial_data6 = adc_P * adc_P
        partial_data2 = self.P11 * partial_data6 / 65536
        partial_data3 = partial_data2 * adc_P / 128
        partial_data4 = offset / 0x04 + partial_data1 + partial_data5 \
            + partial_data3
        comp_press = partial_data4 * 25 / 1099511627776
        return comp_press
    def get_temperature_and_pressure_and_altitude(self):
        """Returns pressure in Pa as double. Output value of "6386.2"equals 96386.2 Pa = 963.862 hPa."""
        xlsb = self._read_byte(BMP388_REG_ADD_TEMP_XLSB)
        lsb = self._read_byte(BMP388_REG_ADD_TEMP_LSB)
        msb = self._read_byte(BMP388_REG_ADD_TEMP_MSB)
        adc_T = (msb << 0x10) + (lsb << 0x08) + xlsb
        temperature = self.compensate_temperature(adc_T)
        xlsb = self._read_byte(BMP388_REG_ADD_PRESS_XLSB)
        lsb = self._read_byte(BMP388_REG_ADD_PRESS_LSB)
        msb = self._read_byte(BMP388_REG_ADD_PRESS_MSB)
        adc_P = (msb << 0x10) + (lsb << 0x08) + xlsb
        pressure = self.compensate_pressure(adc_P)
        altitude = 4433000 * (0x01 - pow(pressure / 100.0 / 101325.0,
                              0.1903))
        return (temperature, pressure, altitude)
if __name__ == '__main__':
 import time
 
 print("BMP388 Test Program ...\n")
 
 bmp388 = BMP388()
    
 while True:
  time.sleep(0.5)
  temperature,pressure,altitude = bmp388.get_temperature_and_pressure_and_altitude()
  print(' Temperature = %.1f Pressure = %.2f  Altitude =%.2f '%(temperature/100.0,pressure/100.0,altitude/100.0))

Peter --OzzMaker.com --

[johnmark]

A partial success: We tabbed through the code, but got an error:

AttributeError: ‘BMP388’ object has no attribute ‘T1’.

To us, it seemed like the function _load_calibration(): was never being called, so we added a line bmp388._load_calibration()  in to the  if __name__ = ‘__main__’:  module. Edit for clarity, we added this line right after the line bmp388=BMP388() which declares the object.

Now the program executes, but all the data is stale.

Temperature = 23.7 Pressure = 79241.63 Altitude =2026.07

Any thoughts?

 

[johnmark]

Solved:

The code supplied above by Peter is correct. When copy-pasting, we lost indentations, and did not do it properly ourselves. The proper indentation must be used. Here is a link to a location that we found the same code, but with indents intact for the BerryGPS v3.5

TLDR: Use this code for the BMP388 temp/pressure/altimeter

https://github.com/getelectronics/PIBits/blob/master/python/bmp388.py

Cheers, and thank you Peter for all the support.

[jimb]

Hi johnmark, I was happy to see your post….

I am running your code from github with the BerryGPS-IMU but, I always get the message “Pressure sersor NULL!” followed by:

Temperature = 0.0 Pressure = 0.0  Altitude =44330.00
Temperature = 0.0 Pressure = 0.0  Altitude =44330.00
Temperature = 0.0 Pressure = 0.0  Altitude =44330.00
….

The GPS and IMU are both working as expected.

Do you have an pointers based on your experience?

Thank you!

[johnmark]

Here are some things that we checked

• Check which berryGPS version … it was found that we have the bmp388, rather than the bmp280. .
  • Per Peter’s comment above, “Can you check on the back of the PCB and see what version you have?  if you have version 3.5, then it would be using the BMP388.”
  • If you have the older version of the berryGPS, which has a bmp280, you will need different code, which can be found above in the first post on this thread.
• Ensure that I2C is enabled under the raspi-config > interfaces menu, and that I2C is reading that register 0x77 is occupied  (as shown in the IMU guide here: https://ozzmaker.com/berryimu/

Those would be my best guesses where to start based on our team’s experience.
Keep us updated and good luck.

[jimb]

Thank you very much for your kind reply. It turns out that indeed, I have a V2 BerryGPS-IMU so, when I use the BMP280 code everything runs as expected. Thank you again for your help.

[Author]

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