ADM1177 no-OS Driver

Supported Devices

Overview

The ADM1177 is an integrated hot swap controller that offers digital current and voltage monitorng via an on-chip, 12 bit analog-to-digital converter (ADC), communicated through an I2C interface.

The 12 bit ADC can measure the current seen in the sense resistor, as well as the supply voltage on the VCC pin. Measurements can be initiated by an I2C command.

Applications

Power monitoring/power budgeting
Central office equipment
Telecommunications and data communications equipment PCs/servers

ADM1177 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) as mentioned above.

The first API to be called is adm1177_init. Make sure that it returns 0, which means that the driver was initialized correctly.

Range Configuration

By default, the device uses 26.35V range configuration. You may modify this value to 6.65V by using adm1177_set_vrange API.

ADM1177 Device Measurements

Write Operation

In order to communicate to the ADC what data you want to read, you will need to call the adm1177_write API, and at the reg_address put 0 so you will perform a write command operation.

If you want to perform a write extended command operation, you will need to call the same API but at the reg_address put the specific register address corresponding to the extended command you want to perform.

Status Read

In order to read the status, after you used the adm1177_write API, with the command corresponding to the Status Reading Operation, you will need to call the adm1177_read_status API and a status_byte will be returned through the status_byte pointer.

Conversion Data

In order to read the Current, Voltage or Both data form the ADC, after you used the adm1177_write API to tell the ADC you need Voltage, Current or Both, use the adm1177_read_conv API, and voltage and current data will be received through conv_voltage and conv_current pointers.

Raw Sample to True value

If you want the raw data received from the ADC through the previously mentioned pointers converted to real-life values, use the adm1177_to_microvolts API for voltage and adm1177_to_microampers API for current.

ADM1177 Driver Initialization Example

struct adm1177_dev *adm1177;
//Particular I2C Configuration
struct adm1177_init_param adm1177_ip = {
        .i2c_init = {
                .device_id = I2C_DEVICE_ID,
                .slave_address = ADM1177_ADDRESS,
                .extra = I2C_EXTRA,
                .platform_ops = I2C_OPS,
                .max_speed_hz = 100000,
        },
};
uint8_t status_byte;
uint16_t conv_voltage, conv_current;
uint64_t voltage, current;

ret = adm1177_init(&adm1177, &adm1177_ip);
if(ret)
        goto error;

// Initialize the continuous voltage and crurrent readback.
ret = adm1177_write(adm1177, ADM1177_CMD_V_CONT | ADM1177_CMD_I_CONT, 0);
if(ret)
        goto error;

ret = adm1177_read_conv(adm1177, &conv_voltage, &conv_current);
if(ret)
        goto error;

ret = adm1177_to_microvolts(adm1177, conv_voltage, &voltage);
if(ret)
        goto error;

ret = adm1177_to_microampers(conv_current, &current);
if(ret)
        goto error;

ADM1177 no_OS IIO Support

The ADM1177 IIO driver comes on top of ADM1177 driver and offers support for interfacing IIO clients through IIO lib.

ADM1177 Device Configuration

Device Attributes

ADM1177 IIO device does not have any device specific attributes.

Device Channels

ADM1177 IIO device has 0 output channels and 2 input channels: 1 voltage channel and 1 current channel.

Voltage Channel

The voltage channel is:

Channel 0: Voltage

The voltage channel has 2 attributes:

raw - the raw voltage value read from the device.
scale - is the scale that has to be applied to the raw value in order to obtain the converted real value in Volts. It depends on the ADC V Range and has a specific formula.

In order to obtain the value in the V units, raw has to be scaled by scale:

converted_voltage [V] = raw * scale
converted_voltage [V] = raw * (vrange/4096)

Current Channel

The voltage channel is:

Channel 1: Current

The voltage channel has 2 attributes:

raw - the raw currrent value read from the device.
scale - is the scale that has to be applied to the raw value in order to obtain the converted real value in mA. It depends on the ADC I_FULLSCALE and has a specific formula.

In order to obtain the value in the mA units, raw has to be scaled by scale:

converted_current [V] = raw * scale
converted_current [V] = raw * (I_FULLSCALE*R_SENSE/4096)

Device buffers

The ADM1177 IIO devices driver supports the usage of a data buffer for reading purposes.

ADM1177 IIO Driver Initialization Example

#define DATA_BUFFER_SIZE 400
uint16_t iio_data_buffer[DATA_BUFFER_SIZE*2*sizeof(int)];

struct adm1177_iio_dev *adm1177_iio_dev = NULL;
struct adm1177_iio_init_param adm1177_iio_init_param;

struct iio_app_desc *app;
struct iio_data_buffer adm1177_buff = {
        .buff = (void *)iio_data_buffer,
        .size = DATA_BUFFER_SIZE*2*sizeof(int),
};
struct iio_app_init_param app_init_param = { 0 };

struct adm1177_init_param adm1177_ip = {
        .i2c_init = {
                .device_id = I2C_DEVICE_ID,
                .slave_address = ADM1177_ADDRESS,
                .extra = I2C_EXTRA,
                .platform_ops = I2C_OPS,
                .max_speed_hz = 100000,
        },
};

adm1177_iio_init_param.adm1177_initial = &adm1177_ip;
ret = adm1177_iio_init(&adm1177_iio_dev, &adm1177_iio_init_param);
if(ret)
        goto error;

struct iio_app_device iio_devices[] = {
        {
                .name = "adm1177",
                .dev = adm1177_iio_dev,
                .dev_descriptor = adm1177_iio_dev->iio_dev,
                .read_buff = &adm1177_buff,
        },
};

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

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

return iio_app_run(app);