279 lines
9.8 KiB
Markdown
279 lines
9.8 KiB
Markdown
# I2C Master Driver :id=i2c-master-driver
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The I2C Master drivers used in QMK have a set of common functions to allow portability between MCUs.
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## I2C Addressing :id=note-on-i2c-addresses
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All of the addresses expected by this driver should be pushed to the upper 7 bits of the address byte. Setting
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the lower bit (indicating read/write) will be done by the respective functions. Almost all I2C addresses listed
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on datasheets and the internet will be represented as 7 bits occupying the lower 7 bits and will need to be
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shifted to the left (more significant) by one bit. This is easy to do via the bitwise shift operator `<< 1`.
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You can either do this on each call to the functions below, or once in your definition of the address. For example, if your device has an address of `0x18`:
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```c
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#define MY_I2C_ADDRESS (0x18 << 1)
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```
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See https://www.robot-electronics.co.uk/i2c-tutorial for more information about I2C addressing and other technical details.
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## AVR Configuration :id=avr-configuration
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The following defines can be used to configure the I2C master driver:
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|`config.h` Override|Description |Default |
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|-------------------|---------------------|--------|
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|`F_SCL` |Clock frequency in Hz|`400000`|
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No further setup is required - just connect the `SDA` and `SCL` pins of your I2C devices to the matching pins on the MCU:
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|MCU |`SCL`|`SDA`|
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|------------------|-----|-----|
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|ATmega16/32U4 |`D0` |`D1` |
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|AT90USB64/128 |`D0` |`D1` |
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|ATmega32A |`C0` |`C1` |
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|ATmega328/P |`C5` |`C4` |
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?> The ATmega16/32U2 does not possess I2C functionality, and so cannot use this driver.
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## ChibiOS/ARM Configuration :id=arm-configuration
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You'll need to determine which pins can be used for I2C -- a an example, STM32 parts generally have multiple I2C peripherals, labeled I2C1, I2C2, I2C3 etc.
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To enable I2C, modify your board's `halconf.h` to enable I2C:
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```c
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#define HAL_USE_I2C TRUE
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```
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Then, modify your board's `mcuconf.h` to enable the peripheral you've chosen, for example:
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```c
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#undef STM32_I2C_USE_I2C2
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#define STM32_I2C_USE_I2C2 TRUE
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```
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|`mcuconf.h` Setting |Description |Default|
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|----------------------------|----------------------------------------------------------------------------------|-------|
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|`STM32_I2C_BUSY_TIMEOUT` |Time in milliseconds until the I2C command is aborted if no response is received |`50` |
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|`STM32_I2C_XXX_IRQ_PRIORITY`|Interrupt priority for hardware driver XXX (THIS IS AN EXPERT SETTING) |`10` |
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|`STM32_I2C_USE_DMA` |Enable/Disable the ability of the MCU to offload the data transfer to the DMA unit|`TRUE` |
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|`STM32_I2C_XXX_DMA_PRIORITY`|Priority of DMA unit for hardware driver XXX (THIS IS AN EXPERT SETTING) |`1` |
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Configuration-wise, you'll need to set up the peripheral as per your MCU's datasheet -- the defaults match the pins for a Proton-C, i.e. STM32F303.
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|`config.h` Overrride |Description |Default|
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|------------------------|--------------------------------------------------------------|-------|
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|`I2C_DRIVER` |I2C peripheral to use - I2C1 -> `I2CD1`, I2C2 -> `I2CD2` etc. |`I2CD1`|
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|`I2C1_SCL_PIN` |The pin definition for SCL |`B6` |
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|`I2C1_SCL_PAL_MODE` |The alternate function mode for SCL |`4` |
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|`I2C1_SDA_PIN` |The pin definition for SDA |`B7` |
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|`I2C1_SDA_PAL_MODE` |The alternate function mode for SDA |`4` |
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The following configuration values depend on the specific MCU in use.
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### I2Cv1 :id=i2cv1
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* STM32F1xx
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* STM32F2xx
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* STM32F4xx
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* STM32L0xx
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* STM32L1xx
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See [this page](https://www.playembedded.org/blog/stm32-i2c-chibios/#7_I2Cv1_configuration_structure) for the I2Cv1 configuration structure.
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|`config.h` Override|Default |
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|-------------------|----------------|
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|`I2C1_OPMODE` |`OPMODE_I2C` |
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|`I2C1_CLOCK_SPEED` |`100000` |
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|`I2C1_DUTY_CYCLE` |`STD_DUTY_CYCLE`|
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### I2Cv2 :id=i2cv2
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* STM32F0xx
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* STM32F3xx
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* STM32F7xx
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* STM32L4xx
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See [this page](https://www.playembedded.org/blog/stm32-i2c-chibios/#8_I2Cv2_I2Cv3_configuration_structure) for the I2Cv2 configuration structure.
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|`config.h` Override |Default|
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|---------------------|-------|
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|`I2C1_TIMINGR_PRESC` |`0U` |
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|`I2C1_TIMINGR_SCLDEL`|`7U` |
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|`I2C1_TIMINGR_SDADEL`|`0U` |
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|`I2C1_TIMINGR_SCLH` |`38U` |
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|`I2C1_TIMINGR_SCLL` |`129U` |
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## Functions :id=functions
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### `void i2c_init(void)`
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Initialize the I2C driver. This function must be called only once, before any of the below functions can be called.
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This function is weakly defined, meaning it can be overridden if necessary for your particular use case:
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```c
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void i2c_init(void) {
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setPinInput(B6); // Try releasing special pins for a short time
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setPinInput(B7);
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wait_ms(10); // Wait for the release to happen
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palSetPadMode(GPIOB, 6, PAL_MODE_ALTERNATE(4) | PAL_STM32_OTYPE_OPENDRAIN | PAL_STM32_PUPDR_PULLUP); // Set B6 to I2C function
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palSetPadMode(GPIOB, 7, PAL_MODE_ALTERNATE(4) | PAL_STM32_OTYPE_OPENDRAIN | PAL_STM32_PUPDR_PULLUP); // Set B7 to I2C function
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}
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```
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---
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### `i2c_status_t i2c_start(uint8_t address, uint16_t timeout)`
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Start an I2C transaction.
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#### Arguments
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- `uint8_t address`
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The 7-bit I2C address of the device (ie. without the read/write bit - this will be set automatically).
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_transmit(uint8_t address, uint8_t *data, uint16_t length, uint16_t timeout)`
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Send multiple bytes to the selected I2C device.
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#### Arguments
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- `uint8_t address`
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The 7-bit I2C address of the device.
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- `uint8_t *data`
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A pointer to the data to transmit.
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- `uint16_t length`
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The number of bytes to write. Take care not to overrun the length of `data`.
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_receive(uint8_t address, uint8_t* data, uint16_t length, uint16_t timeout)`
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Receive multiple bytes from the selected SPI device.
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#### Arguments
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- `uint8_t address`
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The 7-bit I2C address of the device.
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- `uint8_t *data`
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A pointer to the buffer to read into.
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- `uint16_t length`
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The number of bytes to read. Take care not to overrun the length of `data`.
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_writeReg(uint8_t devaddr, uint8_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout)`
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Writes to a register with an 8-bit address on the I2C device.
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#### Arguments
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- `uint8_t devaddr`
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The 7-bit I2C address of the device.
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- `uint8_t regaddr`
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The register address to write to.
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- `uint8_t *data`
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A pointer to the data to transmit.
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- `uint16_t length`
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The number of bytes to write. Take care not to overrun the length of `data`.
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_writeReg16(uint8_t devaddr, uint16_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout)`
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Writes to a register with a 16-bit address (big endian) on the I2C device.
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#### Arguments
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- `uint8_t devaddr`
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The 7-bit I2C address of the device.
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- `uint16_t regaddr`
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The register address to write to.
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- `uint8_t *data`
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A pointer to the data to transmit.
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- `uint16_t length`
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The number of bytes to write. Take care not to overrun the length of `data`.
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_readReg(uint8_t devaddr, uint8_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout)`
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Reads from a register with an 8-bit address on the I2C device.
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#### Arguments
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- `uint8_t devaddr`
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The 7-bit I2C address of the device.
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- `uint8_t regaddr`
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The register address to read from.
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- `uint16_t length`
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The number of bytes to read. Take care not to overrun the length of `data`.
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_readReg16(uint8_t devaddr, uint16_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout)`
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Reads from a register with a 16-bit address (big endian) on the I2C device.
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#### Arguments
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- `uint8_t devaddr`
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The 7-bit I2C address of the device.
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- `uint16_t regaddr`
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The register address to read from.
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- `uint16_t length`
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The number of bytes to read. Take care not to overrun the length of `data`.
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- `uint16_t timeout`
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The time in milliseconds to wait for a response from the target device.
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#### Return Value
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`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
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---
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### `i2c_status_t i2c_stop(void)`
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Stop the current I2C transaction.
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