# BME280 No GND on QW/ST Cable?

**URL:** <https://forums.pimoroni.com/t/bme280-no-gnd-on-qw-st-cable/24173>\
**Category:** Support\
**Created:** [February 13, 2024, 12:10pm UTC](https://forums.pimoroni.com/t/bme280-no-gnd-on-qw-st-cable/24173 "2024-02-13T12:10:57Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ImogenWren](https://avatars.discourse-cdn.com/v4/letter/i/c2a13f/32.png) [@ImogenWren](https://forums.pimoroni.com/u/ImogenWren)\
**Post date:** [February 13, 2024, 12:10pm UTC](https://forums.pimoroni.com/t/bme280-no-gnd-on-qw-st-cable/24173/1 "2024-02-13T12:10:57Z")

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I have a couple of BME280 PCBs, I am not measuring continuity between GND and the black V- wire on the QW/ST connector. All the other pinouts seem correct. Is there a known issue with this board? Is black not suppost to be connected to GND? Is it connected to anything else or am I able to just short them together on the board?

Is there a schematic for this PCB available anywhere?

EDIT:  
Turns out the Adafruit library for the BME280 uses a 0x6\* address, not 0x76. I made sure to pass the correct i2C address in the .begin statement and its now functioning. This issue was why I had started chasing grounds. Note to the manufacturer, a little LED on the board is a very useful diagnostic tool!

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**Author:** ![hel](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/hel/32/6075_2.png) [@hel](https://forums.pimoroni.com/u/hel)\
**Post date:** [February 13, 2024, 12:19pm UTC](https://forums.pimoroni.com/t/bme280-no-gnd-on-qw-st-cable/24173/2 "2024-02-13T12:19:05Z")

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Hi Imogen

The schematic is linked on the shop page, here’s a direct link:

> **[BME280\_breakout\_schematic.pdf](https://cdn.shopify.com/s/files/1/0174/1800/files/BME280_breakout_schematic.pdf?v=1650376945)**
>
> 29.20 KB

I think it’s the reverse polarity protection on the ground line that’s interfering with your continuity measuring.

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**Author:** ![alphanumeric](https://sea2.discourse-cdn.com/flex016/user_avatar/forums.pimoroni.com/alphanumeric/32/2729_2.png) [@alphanumeric](https://forums.pimoroni.com/u/alphanumeric)\
**Post date:** [February 13, 2024, 2:16pm UTC](https://forums.pimoroni.com/t/bme280-no-gnd-on-qw-st-cable/24173/3 "2024-02-13T14:16:27Z")

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I have a BME280 connected to my Galactic Unicorn via a QWICC cable. I haven’t measured the continuity but it is working fine. So is a RV3028 that is soldered to the BME280. They are both communicating via the QWICC cable / connectors.