I2C si7055

[John]

I have an si7055 i2c temperature sensor connected to an nRF52840

I've tried my best to get a reading, but failed.

Therefore given up.

I'd be grateful for some help to determine what I've done wrong please.

I've included the project in zipped form for board nrf52840dk.nrf52840

Bluetooth-i2c.zip

[Jørgen Holmefjord]

Hi,

Could you explain a bit more what is failing and what you have tried?

I do not have the sensor available, so I cannot fully test your example, but I did connect a logic analyzer to verify that a write setup for address 0x40 is output on the TWI bus. A NACK is received, as the sensor is not connected.

Have you checked the bus on your end with a logic analyzer, to see what happens? 

Best regards,
Jørgen

[John]

Unfortunately I do not have a logic analyzer.

I am running the code on SDK v1.4.2

I modified si7055.c which is why i2c master found is displayed in the following output. However I receive the same message if I change the address of the sensor in the overlay. I have checked that the correct address is recorded in zephyr.dts 

I'd be grateful if you would check that the overlay included in the project is correctly recording:

SDA 24

SCL 25

si7055 address 0x40

Therefore I'm expecting that regardless of what the logic analyzer is showing you that the call to si7055_init will confirm that the sensor is present.

static int si7055_init(const struct device *dev)

{
struct si7055_data *drv_data = dev->data;

drv_data->i2c_dev = device_get_binding(
DT_INST_BUS_LABEL(0));

if (!drv_data->i2c_dev) {
LOG_ERR("i2c master not found.");
return -EINVAL;
} else {
printk("i2c master found\n");
}

LOG_DBG("si7055 init ok");

return 0;
}

i2c master found
*** Booting Zephyr OS build v2.4.0-ncs2 ***
[00:00:03.000,396] [1;31m<err> i2c_nrfx_twim: Error 195952641 occurred for message 0[0m
[00:00:03.000,427] [1;31m<err> si7055: read register err[0m
sample fetch error
[00:00:06.000,671] [1;31m<err> i2c_nrfx_twim: Error 195952641 occurred for message 0[0m
[00:00:06.000,671] [1;31m<err> si7055: read register err[0m
[

There seem to be a few issues with the sensor.h implementation as indicated in the following 2 links:

https://devzone.nordicsemi.com/f/nordic-q-a/70514/i2c_burst_read-and-i2c_burst_write-not-working-on-nrf5340

https://devzone.nordicsemi.com/f/nordic-q-a/69828/i2c_burst_write-difference-nrf52-and-nrf91-series/290657#290657

[John]

Ok, fixed it.

Very simple, miscommunication with our engineer regarding the SCL and SDA pins.