pw_i2c_mcuxpresso#

NXP MCUXpresso SDK implementation for pw_i2c

Stable C++

pw_i2c_mcuxpresso implements the pw_i2c interface using the NXP MCUXpresso SDK.

The implementation is based on the i2c driver in SDK. I2C transfers use non-blocking driver API.

McuxpressoInitiator implements the pw_i2c initiator interface using the MCUXpresso FlexComm driver.

FlexIoMcuxpressoInitiator implements the pw_i2c initiator interface using the MCUXpresso FlexIo driver. As the FlexIo peripheral emulates I2C, it has a few limitations:

  1. No Clock Stretching support.

  2. No Arbitration support in multi-controller buses.

  3. No proper differentiation between overflow and NACK.

  4. No I2C transfer-flag support, i.e. no support for NO_START, REPEATED_START and NO_STOP flags. This only allows support for:

  • Single Read or Write operations.

  • Write+Read, for example to query a register value on the device.

I3cMcuxpressoInitiator implements the pw_i2c initiator interface using the MCUXpresso I3C driver. It exposes a few I3C specific API’s for setting up the bus, allowing normal I2C API’s to work after setup.

Setup#

This module requires following setup:

  1. Use pw_build_mcuxpresso to create a pw_source_set for an MCUXpresso SDK.

  2. Include the i2c driver component in this SDK definition.

  3. Specify the pw_third_party_mcuxpresso_SDK GN global variable to specify the name of this source set.

  4. Use pw::i2c::McuxpressoInitiator implementation of pw::i2c::Initiator while creating pw::i2c::Device or pw::i2c::RegisterDevice interface to access the I2C devices connected to target.

Usage#

McuxpressoInitiator example usage.

pw::clock_tree::Element& flexcomm11_clock;

constexpr uint32_t kI2CBaudRate = 100000;
constexpr McuxpressoInitiator::Config kConfig = {
    .flexcomm_address = I2C11_BASE,
    .clock_name = kCLOCK_Flexcomm11Clk,
    .baud_rate_bps = kI2CBaudRate,
};
McuxpressoInitiator initiator{kConfig, flexcomm11_clock};
initiator.Enable();

FlexIoMcuxpressoInitiator example usage.

Note

The flexio_sda_channel and flexio_scl_channel are platform-specific. The NXP MCUXpresso ConfigTool can be used to auto-generate a definition after setting an “identifier” to the associated FlexIo pins. The value is an enumeration from 0 to the max number of FlexIo pins supported by the MCU.

pw::clock_tree::Element& flexio_clock;

constexpr uint32_t kI2CBaudRate = 100000;
constexpr FlexIoMcuxpressoInitiator::Config kFlexioConfig = {
    .flexio_address = FLEXIO0_BASE,
    .clock_name = kCLOCK_FlexioClk,
    .baud_rate_bps = kI2CBaudRate,
    .flexio_sda_channel = BOARD_FLEXIO_I2C_SDA_CHANNEL,
    .flexio_scl_channel = BOARD_FLEXIO_I2C_SCL_CHANNEL,
};
FlexIoMcuxpressoInitiator initiator{kFlexioConfig, flexio_clock};
initiator.Enable();

I3cMcuxpressoInitiator example usage.

pw::clock_tree::Element& i3c_clock;

constexpr I3cMcuxpressoInitiator::Config kI3c0Config = {
    .base_address = I3C0_BASE,
    .i2c_baud_rate = kI3cI2cBaudRate,
    .i3c_open_drain_baud_rate = kI3cOpenDrainBaudRate,
    .i3c_push_pull_baud_rate = kI3cPushPullBaudRate,
    .enable_open_drain_stop = false,  // NXP default
    .enable_open_drain_high = true,   // necessary to allow bus to operate in
                                      // mixed mode
};

I3cMcuxpressoInitiator i3c_0_initiator{kI3c0Config, i3c_clock};

// Initialize the i3c core library. After this is called, the
// initiator can be used for regular i2c communication.
i3c_0_initiator.Enable();

// Perform an i3c bus initialization by assigning the following targets
// their i2c static address as their i3c dynamic address.
constexpr std::array<pw::i2c::Address, 2> kI3cTargets = {
    pw::i2c::Address::SevenBit<0x23>(),
    pw::i2c::Address::SevenBit<0x38>(),
};
i3c_initiator.SetStaticAddressList(kI3cTargets);
PW_TRY(i3c_initiator.Initialize());

I3cMcuxpressoInitiator example of a individual static i3c devices that comes on and offline to save power.

constexpr I3cMcuxpressoInitiator::Config kI3c0Config = {
    .base_address = I3C0_BASE,
    .i2c_baud_rate = kI3cI2cBaudRate,
    .i3c_open_drain_baud_rate = kI3cOpenDrainBaudRate,
    .i3c_push_pull_baud_rate = kI3cPushPullBaudRate,
    .enable_open_drain_stop = false,  // NXP default
    .enable_open_drain_high = true,   // necessary to allow bus to operate in
                                      // mixed mode
};

I3cMcuxpressoInitiator i3c_0_initiator{kI3c0Config};

// Initialize the i3c core library. After this is called, the
// initiator can be used for regular i2c communication.
i3c_0_initiator.Enable();

constexpr auto address = pw::i2c::Address::SevenBit<0x58>();

// Assign a fixed i3c address from the static i2c address.
i3c_0_initiator.SetDasa(address);

// i3c read write activity against address

// Power off device.

// Tell the initiator that the address is no longer assigned.
i3c_0_initiator.ForgetAssignedAddress(address);

// Optionally disable the initiator to bring the SDA/SCL lines low.
// i3c_0_initiator.Disable();
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