I2C Errors

[NikTheGreek]

Hi.
some time ago i bought two I2C modules.
BMP085
http://www.ebay.com/itm/BMP085-I2C-Digi ... 2573275444
and HMC5883L
http://www.ebay.com/itm/HMC5883L-Triple ... 25724aa8a0

Each one working fine when connected to my FC (328p) + WMP+NUNCHUCK no errors

BUT..

When connected all together in my FC the WMP+Nunchuck are disabled and not working and im taking I2C errors.

Any idea WHY ???

[copterrichie]

Maybe pullup resistant or I2C address conflicts.

[mr.rc-cam]

Your BMP085 board needs an LLC. The HMC5883L has one built in, so you could connect the BMP085 directly to its LLC circuitry to achieve this. If you post the schematic to the HMC5883 board then someone here can advise where to solder the BMP085 to it. Otherwise, you will need to use an external LLC with your BMP085.

Also, in the photo of your HMC5883 I see that the installed i2c pullups are 10K ohms. This value is too high for best i2c reliability. The preferred pullup value is 2.2K ohms, so you will need to add external i2c pullups (3K ohms would be fine).

- Thomas

[NikTheGreek]

Also, in the photo of your HMC5883 I see that the installed i2c pullups are 10K ohms. This value is too high for best i2c reliability. The preferred pullup value is 2.2K ohms, so you will need to add external i2c pullups (3K ohms would be fine).

I use external PulUps 4,6 K

Your BMP085 board needs an LLC. The HMC5883L has one built in, so you could connect the BMP085 directly to its LLC circuitry to achieve this. If you post the schematic to the HMC5883 board then someone here can advise where to solder the BMP085 to it. Otherwise, you will need to use an external LLC with your BMP085.

Then i have to ask the schematic from the seller.
But if this is the case then WHY is working fine when connected to my FC ??

Thank you both for your valuable answers.

[mr.rc-cam]

But if this is the case then WHY is working fine when connected to my FC ??

1. With only one sensor installed the i2c traffic is lower, so marginal i2c signals may still work.
2. With both sensors installed you are mixing 3.3V and 5V i2c logic together, which can affect reliability.

Please read the first post in the following old discussion. It was aimed at V1.9 users, but the i2c hardware issues are the same for any installation. After you have read it, re-read it several more times until all the i2c hardware issues are clearly understood.
viewtopic.php?f=8&t=986

- Thomas

[NikTheGreek]

Thank you once again

[NikTheGreek]

Here are the scematics

[mr.rc-cam]

The schematic of your BMP085 shows that it already has a LLC. So if the posted schematic is accurate for your BMP085 board then it will not need an external LLC.

Use your voltmeter and measure the voltages at these I/O wired locations and report what you find:
1. BMP085 J2 +5V pad. Should be +5V.
2. BMP085 Xclr pad. Should be +2.5V. Nothing should be soldered to this pad!
3. HMC5883L J1 +5V pad. Should be +5V.

Also, change your two external 4.6K pullups. I suggest something between 2.7K to 3.0K ohms. Be sure that the pullups are sourced from 5V.

- Thomas

[NikTheGreek]

2,7 K and the problem SOLVED !!!!!
No errors at all !!!

THANK YOU

[mr.rc-cam]

Congratulations, you are welcome!

- Thomas