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This version (17 May 2023 09:43) was approved by Jose Ramon San Buenaventura.

Table of Contents

LTC4306 No-OS Driver

Supported Devices

Evaluation Boards


Overview

The LTC4306 is a 4-channel, 2-wire bus multiplexer with bus buffers to provide capacitive isolation between the upstream bus and downstream buses. Through software control, the LTC4306 connects the upstream 2-wire bus to any desired combination of downstream buses. Each channel can be pulled up to a supply voltage ranging from 2.2 V to 5.5 V, independent of the LTC4306 supply voltage. The downstream channels are also provided with ALERT1-ALERT4 inputs for fault reporting.

Programmable timeout circuitry disconnects the downstream buses if the bus is stuck low. When activated, rise time accelerators source currents into the 2-wire bus pins to reduce rise time. Driving the ENABLE pin low restores all features to their default states. Three address pins provide 27 distinct addresses.

Applications

  • Nested Addressing
  • 5 V / 3.3 V Level Translator
  • Capacitance Buffer/Bus Extender

ADI No-OS

The goal of the ADI Microcontroller No-OS is to provide reference projects for lower end processors, which can't run Linux or aren't running a specific operating system, and to help those customers using microcontrollers with ADI parts. ADI No-OS offers generic drivers, which can be used as a base for any microcontroller platforms; and also provides example projects, which are using these drivers on various microcontroller platforms.

For more information about ADI No-OS and supported microcontroller platforms, visit the No-OS User Guide.

LTC4306 ADI No-OS driver

Driver Source Code

The source code for LTC4306 driver can be found here:

This driver also uses the ADI utility library, so make sure you also add the necessary files to your project. The source code for the utility library can be found here:

To use the LTC4306 No-OS driver, you need to provide the specific implementation for the communication APIs and the specific types they use.
If the I2C communication is chosen, these are the functions to be called by the LTC4306 driver and have to be implemented:

no_os_i2c_init() initializes the communication peripheral
no_os_i2c_write() writes data to the device
no_os_i2c_read() reads data from the device
no_os_i2c_remove() deinitializes the communication peripheral

And these are the two data types that have to be defined:

no_os_i2c_desc structure holding the I2C descriptor
no_os_i2c_init_param structure holding the parameters for I2C initialization

An example of a header file containing the prototypes of the functions which have to be implemented, along with some generic data types they are using, can be found below:

Code Documentation

Source code documentation for the driver is automatically generated using the Doxygen tool and can be accessed in these links:

Device Configuration

Driver Initialization

To use the device, you need to provide the support for the communication protocol (I2C) as mentioned above.

The first API function to be called is ltc4306_addr_gen to generate the corresponding device's slave address. Once a proper address is generated, use the function ltc4306_init to initialize the device and make sure that it returns 0. This indicates a successful driver initialization.

Device Address Generation

The LTC4306 has the provision for multiple I2C slave addresses through the ADR0, ADR1, ADR2 pins. To generate the proper address, supply the voltage level going into pins ADR0, ADR1, ADR2 to the ltc4306_addr_gen function.

The header file of the LTC4306 driver provides an enumeration for the valid ADR0, ADR1, ADR2 input voltage level values. There are a total of 27 valid slave address combinations that can be generated depending on the voltage level supplied to the address pin. For reference, refer to Table 1 of the LTC4306 data sheet.

Control Register 0

The LTC4306's register 0 contains status indicators for different operational cases. The following driver functions can be used to get the status of any selected operational indicators and use for decision making or other purposes:

ltc4306_downstream_check indicates whether one or more downstream buses is connected to upstream
ltc4306_read_alert_logic_state indicates the logic state of the selected pin
ltc4306_read_failed_conn checks for any failure in upstream-downstream/s connection
ltc4306_get_latched_timeout determines whether a timeout has occurred and not yet been cleared
ltc4306_get_realtime_timeout checks the real-time status of the Stuck Low timeout circuitry
Though Register 0 is a read-only register, it can be written to using the ltc4306_write function to reset the fault circuity after any fault/s have been cleared or resolved. No other functionalities are affected by doing so.



Control Register 1

Rise Time Accelerators

The LTC4306 contains rise time accelerators that source current to the 2-wire bus pins to reduce rise time for both upstream (host side) and downstream (slave). When activated using the ltc4306_set_upstream_accel or ltc4306_set_downstream_accel, the accelerators turn on in a controlled manner and source currents during positive transitions.

The accelerator enable status can be checked using the ltc4306_get_upstream_accel or ltc4306_downstream_accel driver functions.

Refer to the data sheet section on Rise Time Accelerators and other related sections to avoid damaging the device or any connected downstream devices.
GPIO State

The LTC4306 also contains 2 GPIO pins. The logic level can be changed and queried using the ltc4306_set_gpio_output_state and the logic level checking process is best described by the ltc4306_get_gpio_output_state or ltc4306_read_gpio_logic_state functions below:

ltc4306_get_gpio_output_state ltc4306_read_gpio_logic_state
General operation checks the logic state of the corresponding GPIOs 1 or 2; both functions can be used to confirm the actual status of the GPIOs
Specific operation reads from the same bit field that the ltc4306_set_gpio_output_state manipulates reads from a different read-only bit field in the same register


Control Register 2

GPIO Configuration

The LTC4306 GPIO pins can be configured for either input or output operation. When at output mode, the GPIO can be configured as either push-pull or open-drain pull down architecture to match external circuitry requirements, if any. These can be easily achieved using the ltc4306_gpio_configure driver function. The function automatically checks whether the GPIO is configured for input or output and only considers the output architecture when the GPIO is configured as an output.

Connection Requirement

Depending on the requirements, the downstream buses (slave) can be immediately connected to the upstream (host) or not. This is controlled using the ltc4306_set_conn_req and can be polled using the ltc4306_get_conn_req functions.

When enabled, the device requires that the corresponding bus logic state to be HIGH. This can also be queried using ltc4306_read_bus_logic_state separately. This means that a connection will only be allowed from slave to host when SDAx and SCLx are both above 1 V, which can also serve as protection for all connected devices.

Mass Write

Aside from the pin configured address, the LTC4306 also responds to the mass write address 0xBA. This allows multiple LTC4306's to be configured using a single command. This functionality is enabled by default, but can be toggled or queried using the ltc4306_set_mass_write and ltc4306_get_mass_write functions.

When mass write is enabled, multiple LTC4306's can be configured by a single transaction. This can be done by reinitializing any or all device structure/s with an address of 0x5D (0xBA is the Write Address) and sending the command using one device structure with said address. The other LTC4306's will respond to that address and recognize the configuration command.

Timeout Mode

The LTC4306 also includes a timeout circuitry. Depending on the timeout programmed using ltc4306_set_timeout_mode, the stuck low circuitry will wait for a specified amount of time before disconnecting any downstream bus that is stuck at LOW level logic. The currently programmed timeout mode can be queried using ltc4306_get_timeout_mode, if needed.

The valid timeout values are as follows:

LTC4306_DISABLED disable timeout circuitry
LTC4306_30MS 30 mS timeout
LTC4306_15MS 15 mS timeout
LTC4306_7P5MS 7.5 mS timeout


Control Register 3

Downstream Channels

The LTC4306 contains 4 downstream channels where other I2C devices can be connected. The driver function ltc4306_set_downstream_channel allows connection or disconnection of a selected channel.

The status of any channel can be queried using either ltc4306_get_downstream_channel or ltc4306_read_bus_logic_state.

The difference between the two functions lies in the bit field accessed. The field accessed by both the ltc4306_set_downstream_channel and ltc4306_get_downstream_channel is a Read-Write fields, while ltc4306_read_bus_logic_state accesses a Read-only field. Both functions can be used for verification of any channel's connection status in some instances.



Driver Initialization Example

Example Initialization Using Maxim SDK as Platform

	int ret;

	struct max_i2c_init_param ltc4306_extra = {
		.vssel = MXC_GPIO_VSSEL_VDDIOH,
	};

	struct ltc4306_init_param ltc4306_ip = {
		.i2c_init.device_id = 0,
		.i2c_init.max_speed_hz = 100000,
		.i2c_init.extra = &ltc4306_extra,
		.i2c_init.platform_ops = &max_i2c_ops,
	};

	ret = ltc4306_addr_gen(&ltc4306_ip, LTC4306_HIGH, LTC4306_HIGH, LTC4306_HIGH);
	if (ret)
		return ret;

	struct ltc4306_dev *ltc4306_device;

	ret = ltc4306_init(&ltc4306_device, ltc4306_ip);
	if (ret)
		return ret;



Example Initialization Using ADUCM3029 as Platform

	int ret;

	struct ltc4306_init_param ltc4306_ip = {
		.i2c_init.device_id = 0,
		.i2c_init.max_speed_hz = 100000,
		.i2c_init.extra = NULL,
		.i2c_init.platform_ops = &aducm_i2c_ops,
	};

	ret = ltc4306_addr_gen(&ltc4306_ip, LTC4306_HIGH, LTC4306_HIGH, LTC4306_HIGH);
	if (ret)
		return ret;

	struct ltc4306_dev *ltc4306_device;

	ret = ltc4306_init(&ltc4306_device, ltc4306_ip);
	if (ret)
		return ret;



resources/tools-software/uc-drivers/ltc4306.txt · Last modified: 17 May 2023 03:07 by Joyce Velasco

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