BNO055 failure (no ack)

[Hugo]

Hello,

I'm trying to use the Arduino BNO055 shield with PCA10040.
This should be quite easy....but it doesn't work: I can't get any acknoledgement. Arduino use 5V pins, so there is an i²c level converter, I removed and bypassed it, not working better.
I tried the twi scan, and can find a mma7660 directly, but not the BNO055.

Here is the digital analysis, I checked on a scope and integrity seems fine (I can't take screenshot).

I'm quite lost. I don't know if it's on the shield side, some config I didn't see...
here is the schematic of the board:

https://content.arduino.cc/assets/9-AxesMotion-Shield-V8-SCH.pdf

(I removed the PCA9306, and 5k pullup should be really fine)

This is my twi config, but I didn't make any modification on the scanner code... so i don't know it it's sofware.

static void twi_config(void)
{
    uint32_t err_code;

    nrf_drv_twi_config_t const config = {
       .scl                = ARDUINO_SCL_PIN,
       .sda                = ARDUINO_SDA_PIN,
       .frequency          = NRF_DRV_TWI_FREQ_100K,
       .interrupt_priority = APP_IRQ_PRIORITY_LOWEST,
       .clear_bus_init     = false,
       .hold_bus_uninit    = false
    };

    err_code = nrf_drv_twi_init(&twi, &config,NULL,NULL);
    nrf_drv_twi_enable(&twi);
    APP_ERROR_CHECK(err_code);
}

This is the working arduino library (on an arduino mega, just for a test):
github.com/.../BNO055

And of course the datasheet:

https://ae-bst.resource.bosch.com/media/_tech/media/datasheets/BST-BNO055-DS000.pdf

and I2c protocol description from page 90

Any idea? I'm really lost.

[Øyvind]

Hello, 

It's not very clear what you are using. Are you trying to use an Arduino library with our SDK? How did you connect the mma7660?

Are you sure that the BNO055 is powered? Have you measured VDD? Have you tried to debug?

Kind regards,
Øyvind

[Øyvind]

I removed the PCA9306, and 5k pullup should be really fine

 Have you mounted 5k instead of 10k? 4k7 are usually standard and should be sufficient. Are all SDA and SDL lines connected after PCA9306 removal?

-Øyvind

[Hugo]

I found the problem: the reset line is also to d2 by lever converter 74LVC1G125.
There is actually 3 of them: one for the reset button, one for d2 reset, and one in the other way for the interruption pin. It's good remove and shortcut them too.

Maybe there is a better way to trick power sypply of the board and avoid all this changes. But doing it work, and makes it not compliant with original arduino.
on the drawing, I inverting "in" and "out", but they just need to be directly connected.
I couldn't post it earlyier, this topic was unreachable.

[Hugo]

There is 2 10k resistance on each side of the converter. IOREF is connected to VDD (3v) on PCA10040. So it makes a 5k average resistor on lines.
And VDD was very fine, leds was ok. Just the reset line I didn't check well.

[Øyvind]

Glad to hear you found the solution! 

Best regards,
Øyvind