MAX31827 no-OS driver

Supported Devices

Overview

The MAX31827 is a ±1°C accuracy from -40°C to +125°C (12 bits) local temperature switch and sensor with I2C/SMBus interface. The combination of small 6-bump wafer-level package (WLP) and high accuracy makes this temperature sensor/switch ideal for a wide range of applications. It can be used as a temperature switch with preconfigured thresholds and/or as a temperature sensor with I2C interface. When the part operates as an independent temperature switch, the I2C interface doesn’t have to be used. This enables use of the part in systems that require thermal protection implemented in hardware, without the need for reconfiguration or use of software/firmware during normal operation.

Applications

MAX31827

Battery-Powered Equipment
Handheld Electronics
Data Communications Equipment
Servers
Industrial Equipment

MAX31827 Device Configuration

Driver Initialization

In order to be able to use the device, you will have to provide the support for the communication protocol (I2C).

The first API to be called is max31827_init. Make sure that it returns 0, which means that the driver was initialized correctly.

Inside the max31827_init API, max31827_init_client API is called to setup the values inside the Configuration Register.

MAX31827 Device Measurements

Temperature Data (Input)

The data can be obtained by calling max31827_read_temp_input API. The temperature is in milli-degrees Celsius, with scaling already applied.

Temperature Data (Thresholds and Hysteresis)

The data can be obtained by calling max31827_read_temp API. The temperature is in milli-degrees Celsius, with scaling already applied.

Shutdown Write

The max31827_shutdown_write API is used to write in certain registers that needs the device to be in shutdown mode.

Before the Temperature Threshold Alarm, Alarm Hysteresis Threshold and Resolution bits from Configuration register are changed over I2C, the part must be in shutdown mode.

Write Alarm Temperature Values

The max31827_write_alarm_val API is used to write the Temperature Threshold Alarm and Alarm Hysteresis Threshold temperature values.

MAX31827 Driver Initialization Example

struct max31827_device *dev;

struct no_os_uart_init_param uip = {
        .device_id = UART_DEVICE_ID,
        .baud_rate = UART_BAUDRATE,
        .size = NO_OS_UART_CS_8,
        .parity = NO_OS_UART_PAR_NO,
        .stop = NO_OS_UART_STOP_1_BIT,
        .platform_ops = UART_OPS,
        .extra = UART_EXTRA,
};

const struct no_os_i2c_init_param max31827_i2c_ip = {
        .device_id = I2C_DEVICE_ID,
        .max_speed_hz = 100000,
        .slave_address = 0x42,
        .platform_ops = I2C_OPS,
        .extra = I2C_EXTRA,
};

struct max31827_init_param max31827_ip = {
        .i2c_init_param = max31827_i2c_ip,
        .comp_int = 0,
        .alarm_pol = 0,
        .fault_q = 1,
        .timeout_enable = 0,
};

ret = max31827_init(&dev, &max31827_ip);
if (ret)
        goto error;

MAX31827 no-OS IIO support

The MAX31827 IIO driver comes on top of the MAX31827 driver and offers support for interfacing IIO clients through libiio.

MAX31827 IIO Device Configuration

Global Attributes

The device has a total of 10 global attributes:

temp_enable - enables or disables automatic mode
temp_input - Temperature input value in millidegree Celsius
temp_min - Minimum temperature threshold in millidegree Celsius
temp_min_hyst - Minimum temperature hysteresis threshold in millidegree Celsius
temp_min_alarm - Minimum temperature alarm state
temp_max - Maximum temperature threshold in millidegree Celsius
temp_max_hyst - Maximum temperature hysteresis threshold in millidegree Celsius
temp_max_alarm - Maximum temperature alarm state
temp_resolution - Temperature resolution in millidegree Celsius
update_interval - Update interval in milliseconds

MAX31827 IIO Driver Initialization Example

int ret;

struct max31827_iio_device *max31827_iio_dev;
struct max31827_iio_init_param max31827_iio_ip = {
        .max31827_init_param = &max31827_ip,
};

struct iio_app_desc *app;
struct iio_app_init_param app_init_param = {0};

ret = max31827_iio_init(&max31827_iio_dev, &max31827_iio_ip);
if (ret)
        goto exit;

struct iio_app_device iio_devices[] = {
        {
                .name = "max31827",
                .dev = max31827_iio_dev,
                .dev_descriptor = max31827_iio_dev->iio_dev,
        },
};

app_init_param.devices = iio_devices;
app_init_param.nb_devices = NO_OS_ARRAY_SIZE(iio_devices);
app_init_param.uart_init_params = uip;

ret = iio_app_init(&app, app_init_param);
if (ret)
        goto remove_iio_max31827;

return iio_app_run(app);