Help with BME680

General
1

A little bit of topic, but I give up :slight_smile: need help!

I am working on a project with the hopes of using the new mesh as the main MCU, is a new flight computer for our near space program.

I am unable to make this sensor work (BME680) When it is in the board installed it will take all i2c communications down with it. I have a gps sharing the same line with the BME680,and I can’t talk to the gps or BME. Once I remove the sensor from the board, GPS works ( i2c works)

The code is good, I used an i2c scanner, when the sensor is on the PCB no devices found, when it is off the PCB the gps gets found. I tried removing pull-ups and that didn’t solved it either.

Would it be to much to ask to take a look at my work and tell me if you see something wrong?

image

image
image936×948 9.13 KB
image
image1294×1194 10.1 KB
image
image4032×3024 1.28 MB
image
image4032×3024 1.82 MB
image
image4032×3024 2.27 MB

2

How do pins 1 & 7 get to ground in your PCB? I think there is groundplane flowing in there but on your screenshot of the PCB CAD I don’t see it.

3

Thank @bko

They got first to the GPS and then to the BME680

There is a ground plane and a VCC plane too. (The lower capacitor goes to the VCC plane) and also the CS pull up (for I2C select)

03%20PM
03%20PM1522×1488 291 KB
14%20PM
14%20PM1514×1484 334 KB

4

I think your pinout for the BME680 is incorrect. I’m looking at this datasheet: https://cdn-shop.adafruit.com/product-files/3660/BME680.pdf

Vcc should be applied to pins 6 and 8 but in your schematic, it looks like you have them on 8 and 3. The SDA and SCL should be on 3 and 4 but you have them on 6 and 5 respectively. Where did you get the EagleCAD part from?

image
image733×847 76.5 KB

5

That sounds like the problem… Ive got it from Sparkfun!

Let me double check and get back 2 u!
Thanks for the info!

6

That is the problem. I didn’t double check the part vs data sheet. My Bad!

Thanks for the catch I was running crazy!

As a heads up: The wrong part was from SparkFun.

7

I replaced the part from another library. However it seems wrong too. Since my brain is frite can someone take a look and see if what I think it is correct.

In the schematics the pins are now correct, but in the board it seems that this is wrong! In my view this is mirrored! From the data sheet you can see that the top view seems inverted or mirrored.

48%20PM
48%20PM2068×988 119 KB

28%20PM
28%20PM1302×1156 7.41 KB

Crop2
Crop2773×776 83.1 KB

Thoughts?

8

Well. I managed to find an Adafruit part for the sensor and it is correct! So I am using that, I will submit an issue to SparkFun though.

2 Likes
9

It seems that whomever created the parts was using the wrong view (from the bottom). Glad you found a better part. Good to know though. Sucks you have to revise a PCB.

1 Like
10

Sucks big time, but the lesson sticks. Always double check with the data sheet :blush: Thanks for that!

1 Like
11

It doesn’t help that Bosch numbered the pins backwards from normal, either. Pin 1 is in the lower left when you’re looking at the bottom side, not the top side, which is opposite of, say an 8-SOIC.

1 Like
12

It sure does not help! I hope I get this one right :blush:

13

I am finally publishing the board as is. Fixed the BME680 placement issue. However can’t get it to work for some reason. I am suspecting a bad SMD soldering work (PNP).

See if you can sport the problem, but for now here is the project repository:

14

UPDATE:

I re-sodder the BME680 sensor to the board (allegedly with the correct pinout) and sensor still not working :confused:

I need a break! If anyone can take a look… I appreciate it!