Cannot use TWI on nRF51822 with S130-v2.0.1 and nRF_SDK_v12.3

[tk]

Hi, I’m a newbie of nRF SoC. I have a BLE gadget with nRF51822_xxAC that controls LEDs and obtains data from accelerometers through I2C(TWI) devices. The hex file for the gadget software was originally created using nRF_SDK v8 on S110-v8 and compiled using ArmCC (Kei).

I’m trying to port it to newer version SDK and softdevice, nRF_SDK v12.3 and S130-v2.0.1, using GCC. Most of things go well. But I have a trouble with TWI.

Two I2C devices are connected to the nRF51822 at pin#36(SCL),37(SDA) and pin#32(SCL),31(SDA). pin#36,37 and #32,31 may correspond to P00.09 and P00.10 and P00.28 and P00.29, respectively.

According to some TWI examples, I modified the twi initialization function and the read/write function in the gadget software. The initialization by nrf_drv_twi_init() seems to be succeed (no error code returns). However, Any RX ( and TX) fails owing to address NACK. Of course, exactly the same gadget with original software (SDK v8 and S110) works fine, so this would not be a hardware trouble. The configuration (only P0.09 and P0.10) in the software is as follows:

const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(0);
const nrf_drv_twi_config_t twi_conf = {
    .frequency          = (nrf_twi_frequency_t)TWI_DEFAULT_CONFIG_FREQUENCY,   \
    .scl                = 9,                                                                                           \
    .sda                = 10,                                                                                        \
    .interrupt_priority = TWI_DEFAULT_CONFIG_IRQ_PRIORITY,                              \
    .clear_bus_init     = TWI_DEFAULT_CONFIG_CLR_BUS_INIT,                                \
    .hold_bus_uninit    = TWI_DEFAULT_CONFIG_HOLD_BUS_UNINIT,                       \
};

For testing, I checked I2C slave address of those devices using twi_scannar in the SDK_v12.3 example, but I couldn’t any devices at both pin pairs.

What should I do to solve this problem? Any help and suggestions are appreciated!

[FormerMember]

What happens if you test the TWI scanner example in the SDK, does that example work?

[tk]

One of the I2C device is PCA9685BS ( www.nxp.com/.../16-channel-12-bit-pwm-fm-plus-ic-bus-led-controller:PCA9685BS ). I want to access (read) the address 0x85 (because of the device address setting). The device is connected to P00.09 and P00.10. In the test result,device at slave address 0x01 only (if scan start from 0x01) was detected. I mean if I start to scan from address 0x02 then the scanner detect device at 0x02 only.

The other I2C device is LIS2DH ( www.st.com/.../lis2dh12.html ). I want to access the address 0x33. The device is connected to P00.28 and P00.29. In the test result, devices at slave address 0x42, 0x70, 0xc2, 0xf0 were detected.

[FormerMember]

1) Pin P0.9 and P0.10 are on the nRF51-DK by default used by UART. Could you test with some other pins, pins that are not in use by anything else?

2) Could you use a logic analyzer to capture what the transferred signal look like?

[tk]

Thanks for your comments. The circuit of the gadget is printed one, so it's difficult to test other pins.... sorry. Can I change the default setting? Also, I don't have logic analyzer here. I need to get it...

[FormerMember]

Instead of using LOG over UART (if that is what you are using), you can disable logging over UART and use RTT instead. You can change the LOG module settings in sdk_config.h.