LTC2983 no-OS driver#

Supported Devices#

LTC2983

LTC2984

LTC2986

LTM2983

Overview#

The LTC2983 measures a wide variety of temperature sensors and digitally outputs the result, in °C or °F, with 0.1°C accuracy and 0.001°C resolution. The LTC2983 can measure the temperature of virtually all standard (type B, E, J, K, N, S, R, T) or custom thermocouples, automatically compensate for cold junction temperatures and linearize the results. The device can also measure temperature with standard 2-, 3- or 4-wire RTDs, thermistors and diodes. It has 20 reconfigurable analog inputs enabling many sensor connections and configuration options. The LTC2983 includes excitation current sources and fault detection circuitry appropriate for each type of temperature sensor.

The LTC2983 allows direct interfacing to ground referenced sensors without the need for level shifters, negative supply voltages, or external amplifiers. All signals are buffered and simultaneously digitized with three high accuracy, 24-bit ∆∑ ADCs, driven by an internal 15ppm/°C (maximum) reference.

LTC2984, LTC2986, and LTM2985 include an EEPROM for storing custom coefficients and channel configuration data.

The LTC2986/LTC2986-1 are 10-channel software and pin-compatible versions of the 20-channel LTC2983/LTC2984. Additional features include special modes that enable easy protection in universal multi-sensor applications, custom tables for generic ADC readings, and direct temperature readout from active analog temperature sensors. The LTC2986-1 is the EEPROM version of the LTC2986.

The LTM2985 is an isolated 10-channel temperature measurement system software compatible with the LTC2986-1. It provides 5kV isolated power and SPI interface to the precision temperature-to-bits converter.

Applications#

LTC2983#

  • Direct Thermocouple Measurements

  • Direct RTD Measurements

  • Direct Thermistor Measurements

  • Custom Sensor Applications

LTC2983 Device Configuration#

Driver Initialization#

In order to be able to use the device, you will have to provide the support for the communication protocol (SPI) alongside RST GPIO pin.

The first API to be called is ltc2983_init. Make sure that it return 0, which means that the driver was initialized correctly.

Inside the ltc2983_init API, ltc2983_setup API is called to setup the values of the device registers including Channel Assignment.

LTC2983 Device Measurements#

Temperature Data#

In case the operation mode selected includes the temperature measurement, then data can be obtained by calling ltc2983_chan_read API. The temperature is in millidegrees Celsius, with scaling already applied.

If you want to obtain the raw temperature data without any scaling applies, simply call ltc2983_chan_read_raw API.

LTC2983 Driver Initialization Example#

struct ltc2983_dev *ltc2983_dev;
struct ltc2983_rsense ltc2983_rsense_2;
struct ltc2983_thermistor ltc2983_thermistor_8;
struct ltc2983_thermistor ltc2983_thermistor_10;

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_spi_init_param ltc2983_spi_ip = {
        .device_id = SPI_DEVICE_ID,
        .max_speed_hz = SPI_MAX_SPEED,
        .chip_select = SPI_CS,
        .mode = NO_OS_SPI_MODE_0,
        .bit_order = NO_OS_SPI_BIT_ORDER_MSB_FIRST,
        .platform_ops = SPI_OPS,
        .extra = SPI_EXTRA,
        .parent = NULL,
};

const struct no_os_gpio_init_param ltc2983_gpio_rstn = {
        .port = GPIO_RSTN_PORT_NUM,
        .number = GPIO_RSTN_PIN_NUM,
        .platform_ops = GPIO_OPS,
        .extra = GPIO_EXTRA,
};

struct ltc2983_init_param ltc2983_ip = {
        .spi_init = ltc2983_spi_ip,
        .gpio_rstn = ltc2983_gpio_rstn,
        .mux_delay_config_us = 1000,
        .filter_notch_freq = 0,
        .sensors[0] = NULL,
        .sensors[1] = &ltc2983_rsense_2.sensor,
        .sensors[2] = NULL,
        .sensors[3] = NULL,
        .sensors[4] = NULL,
        .sensors[5] = NULL,
        .sensors[6] = NULL,
        .sensors[7] = &ltc2983_thermistor_8.sensor,
        .sensors[8] = NULL,
        .sensors[9] = &ltc2983_thermistor_10.sensor,
        .sensors[10] = NULL,
        .sensors[11] = NULL,
        .sensors[12] = NULL,
        .sensors[13] = NULL,
        .sensors[14] = NULL,
        .sensors[15] = NULL,
        .sensors[16] = NULL,
        .sensors[17] = NULL,
        .sensors[18] = NULL,
        .sensors[19] = NULL,
        .custom_addr_ptr = LTC2983_CUST_SENS_TBL_START_REG,
        .dev_type = ID_LTC2983,
};

/**
* Sense resistor connected to channels 1-2
* Resistance: 2k ohms
*/
struct ltc2983_rsense ltc2983_rsense_2 = {
        .sensor = {
                .chan = 2,
                .type = LTC2983_RSENSE,
        },
        .r_sense_val = { // 10kohms
                .r_sense_val_int = 10000,
        }
};

/**
* Thermistor simulator connected to channel 8
* Sense Resistor: Channel 2
*/
struct ltc2983_thermistor ltc2983_thermistor_8 = {
        .sensor = {
                .chan = 8,
                .type = LTC2983_THERMISTOR_44008_44032,
        },
        .r_sense_chan = 2,
        .sensor_config = 0x2,
        .excitation_current = 0x3,
};

/**
* Thermistor fixed simulator connected to channel 10
* Sense Resistor: Channel 2
* Expected: -30.59 C
*/
struct ltc2983_thermistor ltc2983_thermistor_10 = {
        .sensor = {
                .chan = 10,
                .type = LTC2983_THERMISTOR_44008_44032,
        },
        .r_sense_chan = 2,
        .sensor_config = 0x2,
        .excitation_current = 0x3,
};

ret = ltc2983_init(&ltc2983_dev, &ltc2983_ip);
if (ret)
        goto error;

LTC2983 no-OS IIO support#

The LTC2983 IIO driver comes on top of the LTC2983 driver and offers support for interfacing IIO clients through libiio.

LTC2983 IIO Device Configuration#

Input Channel Attributes#

LTC2983 IIO device has input channels which are either input_tempX or input_voltageX depending on the sensor connected to channel X. The input channel has a total of 2 channel attributes:

  • raw - the raw value read from the device

  • scale - the scale that has to be applied to the raw value in order to obtain the converted real value in mC or mV

LTC2983 IIO Driver Initialization Example#

int ret;

struct ltc2983_iio_dev *ltc2983_iio_dev;
struct ltc2983_iio_dev_init_param ltc2983_iio_ip = {
        .ltc2983_init_param = &ltc2983_ip,
};

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

ret = ltc2983_iio_init(&ltc2983_iio_dev, &ltc2983_iio_ip);
if (ret)
        goto exit;

struct iio_app_device iio_devices[] = {
        {
                .name = "ltc2983",
                .dev = ltc2983_iio_dev,
                .dev_descriptor = ltc2983_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 = ltc2983_uart_ip;

ret = iio_app_init(&app, app_init_param);
if (ret)
        goto remove_iio_ltc2983;

return iio_app_run(app);