GY-87 micropython library

[tttadam]

Hi there,

I wondering is there someone who tried to use GY-87 sensor pack, with lopy4(+pytrack).
I would like to add some redundancy to my project. (Like elevation can come from gps and pressure sensor also).

• Can you recommend me a library what I can use?
• I think I also need some help with the wiring. An SI7021 is already connected to the pytrack, But as far as I know it's possible to use I2C devices serial. So maybe I am good to go? But this has some extra pin, over the tipical 4 wires, what need fo I2C.

Thanks!

[Elizar]

@tttadam I²C bus devices are connected in parallel, SDA at SDA, SCL at SCL and so on. Therefore You need no extra pins.

All I²C bus devices have different device ID numbers (see the datasheet for that ID). So the controller can access each device individually.

[tttadam]

@elizar yes I meant paralel sorry. English is not my first language. I know the teory, but I never used more tahn one I2C sensor. But GY-87 has more pins than Vcc, gnd, scl and sda.

[Elizar]

@tttadam Just have a look at http://www.techmonkeybusiness.com/the-gy87-combined-sensor-test-sketch.html for wiring.

Yes, there are some more pins but you probably don't need them for a start.

[tttadam]

@elizar Thank you, I think the wiring is okay, but I am not sure.
This is what I2C scan returs: [64, 104, 119]
64 for is the si7021 sensor for sure.
But, GY-80 has 3 sensor as far as I know, but the there is only 2 additional on shows up at the scan, 104 and 119.
print(si7021.readRH(), si7021.readTemp()) is working fine.
Now, I need to find a micropython library, can you recommend me one?
Thank you,
Ádám,

[robert-hh]

@tttadam 119 is the address of the BMP180. I have a driver for that at https://github.com/robert-hh/BMP085_BMP180. Do not be confused that the file is called bmp085.py. It cintains the classes for both devices. In fact, they behave identical.

[robert-hh]

@tttadam 104 should be the address of the MPU6050 device,
The hmc5883l device address is told to be 30 decimal. If the SI7021 is also connected, you should get four I2C addresses.
So when connecting the GY-87, you should see that. By the way, the title of your post says GY-80, but you link to the GY87.

[tttadam]

@robert-hh I took some picture of the wiring.
Sorry for the confusion, I will fix the title. The sensor what I have is GY-87. This is where I bought it.

[tttadam]

@robert-hh Thank you for the library, it is working fine! :)
I am checking out something fo MPU6050
But I am still not sure where is the third sensor. mybe the gy87 is damaged?

[robert-hh]

@tttadam I looked for MPU6050 libraries. What I found is for RasPi, but it should be easy to adapt them by replacing the calls for I2C send and receive.
About the third sensor HMC5883L. Acording to the data sheet there is no enable pin. The DRDY signal could come from that chip. You should check whether you init the I2C bust at a baudrate <= 400000, because that is the max rate mentioned in the data sheet.

[tttadam]

@robert-hh
First of all sorry for the long delay.
I just checked, and seems like no, the last sensor didn't show up on i2c.scan()
I checked the documentation and the MPU6050 is has some kind of mode/option, where it's connected to other I2c devices, and gather data from them. Maybe the compass is connected to the mpu6050?

>>> from machine import I2C
>>> i2c = I2C(0, I2C.MASTER, baudrate=400000)
>>> i2c.scan()
[64, 104, 119]
>>>

[robert-hh]

@tttadam I justz received a sample of the board that you have linked. Three observations:

• the HMC5883 does not show up in the i2c.scan(), even if the address is ping'ed.
• the bmp180 returns nonsense-values.
• the pull-up resistor values on the board are pretty low,
  effectively 1.1kOhm. I will look tonight into the signals with an oscilloscope to verify the signal quality.

So all-in-all, the board might just be crap.

[tttadam]

@robert-hh ohhh, I didn't even thought about that. But could be. Can you recommend some other sensor?
pytrack has built-in gyro. what i need pressure, and compass.
(The weather ballon will have a camera, and when it took a picture, I would like to know the direction)

[robert-hh]

@tttadam So, looking at the device and the wiring it seems clear why the HMC5883 is not visible in the scan: it is connected to the MBU6050 slave interface. Still, according to the MPU6050 data sheet, it should be visible, because at start-up the MPU6050 connects the main I2C interface to the aux interface.
The I2C signals are fine.

However, on the board I have the BMP180 is broken. The temperature sensor always returns 229.3°C. At least that helped me to find a signed/unsigned bug in my driver.

[tttadam]

@robert-hh said in GY-87 micropython library:

BMP180

I just checked the bmp18. It's seems something off with the altitude...
(1028 is the current QNH in Budapest)

>>> bmp.sealevel = 1028
>>> bmp.altitude
51.46274
>>> bmp.pressure
1021.34
>>> bmp.temperature
24.2
>>> si7021.readTemp()
22.92749
>>> my_gps.altitude
120.3

So you have any guess how Can I get the compass data?

[robert-hh]

@tttadam The altitude is calculated from the actual pressure and what you enter as sea level pressure, roughly 8.5m/hPa. You can see it in the python script.
The compass chip should be available when the I2C-bus is set to pass-through. I'm trying it at the moment.

[robert-hh]

@tttadam So I found a way to talk to the compass, with the following sequence:

from machine import I2C
i2c=I2C()
i2c.writeto_mem(104, 107, 128) # reset MPU6050
i2c.writeto_mem(104, 107, 0) # disable sleep
i2c.writeto_mem(104, 55, 2)   # enable I2C passthru
i2c.scan()

The scan should show you another I2C address. In my case it is 13, which deviates from the HMV5883 data sheet.

[tttadam]

@robert-hh It's working for me too! :)
Awsome! :)
Now I just need to find a correct library for it.
I will start with this

Can you give me some explonation what happend?
What your overall expression of the board?

[robert-hh]

@tttadam When you do the i2c.scan(), which address is reported for the HMC5883? It puzzles me that my device reports 13 instead of 30, which is the address in all examples.
Besides that, I have the impression that in normal operation the HMC5883 is controlled by the MCU6050 for its own purpose. So you might get the information you need through the MCU6050.
If you ask me about what I did to find that way: I looked at the circuit, read the data sheets and looked at some code examples for the MCU6050.

[tttadam]

@robert-hh

This is what I see. So same for me.

>>> from machine import I2C
>>> i2c = I2C(1)
>>> i2c.scan()
[64, 104, 119]
>>> i2c.writeto_mem(104, 107, 128) # reset MPU6050
>>> i2c.writeto_mem(104, 107, 0) # disable sleep
>>> i2c.writeto_mem(104, 55, 2)   # enable I2C passthru
>>> i2c.scan()
[13, 64, 104, 119]
>>>