The I2C Master drivers used in QMK have a set of common functions to allow portability between MCUs.
## An important note on I2C Addresses :id=note-on-i2c-addresses
## I2C Addressing :id=note-on-i2c-addresses
All of the addresses expected by this driver should be pushed to the upper 7 bits of the address byte. Setting
the lower bit (indicating read/write) will be done by the respective functions. Almost all I2C addresses listed
All of the addresses expected by this driver should be pushed to the upper 7 bits of the address byte. Setting
the lower bit (indicating read/write) will be done by the respective functions. Almost all I2C addresses listed
on datasheets and the internet will be represented as 7 bits occupying the lower 7 bits and will need to be
shifted to the left (more significant) by one bit. This is easy to do via the bitwise shift operator `<< 1`.
shifted to the left (more significant) by one bit. This is easy to do via the bitwise shift operator `<< 1`.
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`:
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`:
`#define MY_I2C_ADDRESS (0x18 << 1)`
```c
#define MY_I2C_ADDRESS (0x18 <<1)
```
See https://www.robot-electronics.co.uk/i2c-tutorial for more information about I2C addressing and other technical details.
|`void i2c_init(void);` |Initializes the I2C driver. This function should be called once before any transaction is initiated. |
|`i2c_status_t i2c_start(uint8_t address, uint16_t timeout);` |Starts an I2C transaction. Address is the 7-bit slave address without the direction bit. |
|`i2c_status_t i2c_transmit(uint8_t address, uint8_t* data, uint16_t length, uint16_t timeout);` |Transmit data over I2C. Address is the 7-bit slave address without the direction. Returns status of transaction. |
|`i2c_status_t i2c_receive(uint8_t address, uint8_t* data, uint16_t length, uint16_t timeout);` |Receive data over I2C. Address is the 7-bit slave address without the direction. Saves number of bytes specified by `length` in `data` array. Returns status of transaction. |
|`i2c_status_t i2c_writeReg(uint8_t devaddr, uint8_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout);` |Same as the `i2c_transmit` function but `regaddr` sets where in the slave the data will be written. |
|`i2c_status_t i2c_readReg(uint8_t devaddr, uint8_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout);` |Same as the `i2c_receive` function but `regaddr` sets from where in the slave the data will be read. |
|`i2c_status_t i2c_stop(void);` |Ends an I2C transaction. |
## AVR Configuration :id=avr-configuration
### Function Return :id=function-return
The following defines can be used to configure the I2C master driver:
All the above functions, except `void i2c_init(void);` return the following truth table:
The following defines can be used to configure the I2C master driver.
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.
|`I2C_DRIVER` |I2C peripheral to use - I2C1 -> `I2CD1`, I2C2 -> `I2CD2` etc. |`I2CD1`|
|`I2C1_BANK` (deprecated)|The bank of pins (`GPIOA`, `GPIOB`, `GPIOC`), superseded by `I2C1_SCL_BANK`/`I2C1_SDA_BANK`|`GPIOB`|
|`I2C1_SCL_BANK` |The bank of pins (`GPIOA`, `GPIOB`, `GPIOC`) to use for SCL |`GPIOB`|
|`I2C1_SCL` |The pin number for SCL (0-15) |`6` |
|`I2C1_SCL_PAL_MODE` |The alternate function mode for SCL |`4` |
|`I2C1_SDA_BANK` |The bank of pins (`GPIOA`, `GPIOB`, `GPIOC`) to use for SDA |`GPIOB`|
|`I2C1_SDA` |The pin number for SDA (0-15) |`7` |
|`I2C1_SDA_PAL_MODE` |The alternate function mode for SDA |`4` |
Lastly, we need to assign the correct GPIO pins depending on the I2C hardware driver we want to use.
The following configuration values depend on the specific MCU in use.
By default the I2C1 hardware driver is assumed to be used. If another hardware driver is used, `#define I2C_DRIVER I2CDX` should be added to the `config.h` file with X being the number of hardware driver used. For example is I2C3 is enabled, the `config.h` file should contain `#define I2C_DRIVER I2CD3`. This aligns the QMK I2C driver with the Chibios I2C driver.
### I2Cv1 :id=i2cv1
STM32 MCUs allows a variety of pins to be configured as I2C pins depending on the hardware driver used. By default B6 and B7 are set to I2C. You can use these defines to set your i2c pins:
| `I2C1_SCL_BANK` | The bank of pins (`GPIOA`, `GPIOB`, `GPIOC`) to use for SCL | `GPIOB` |
| `I2C1_SDA_BANK` | The bank of pins (`GPIOA`, `GPIOB`, `GPIOC`) to use for SDA | `GPIOB` |
| `I2C1_SCL` | The pin number for the SCL pin (0-15) | `6` |
| `I2C1_SDA` | The pin number for the SDA pin (0-15) | `7` |
| `I2C1_BANK` (deprecated) | The bank of pins (`GPIOA`, `GPIOB`, `GPIOC`), superceded by `I2C1_SCL_BANK`, `I2C1_SDA_BANK` | `GPIOB` |
See [this page](https://www.playembedded.org/blog/stm32-i2c-chibios/#7_I2Cv1_configuration_structure) for the I2Cv1 configuration structure.
The ChibiOS I2C driver configuration depends on STM32 MCU:
|`config.h` Override|Default |
|-------------------|----------------|
|`I2C1_OPMODE` |`OPMODE_I2C` |
|`I2C1_CLOCK_SPEED` |`100000` |
|`I2C1_DUTY_CYCLE` |`STD_DUTY_CYCLE`|
STM32F1xx, STM32F2xx, STM32F4xx, STM32L0xx and STM32L1xx use I2Cv1;
STM32F0xx, STM32F3xx, STM32F7xx and STM32L4xx use I2Cv2;
### I2Cv2 :id=i2cv2
#### I2Cv1 :id=i2cv1
STM32 MCUs allow for different clock and duty parameters when configuring I2Cv1. These can be modified using the following parameters, using <https://www.playembedded.org/blog/stm32-i2c-chibios/#I2Cv1_configuration_structure> as a reference:
* STM32F0xx
* STM32F3xx
* STM32F7xx
* STM32L4xx
| Variable | Default |
|--------------------|------------------|
| `I2C1_OPMODE` | `OPMODE_I2C` |
| `I2C1_CLOCK_SPEED` | `100000` |
| `I2C1_DUTY_CYCLE` | `STD_DUTY_CYCLE` |
See [this page](https://www.playembedded.org/blog/stm32-i2c-chibios/#8_I2Cv2_I2Cv3_configuration_structure) for the I2Cv2 configuration structure.
#### I2Cv2 :id=i2cv2
STM32 MCUs allow for different timing parameters when configuring I2Cv2. These can be modified using the following parameters, using <https://www.st.com/en/embedded-software/stsw-stm32126.html> as a reference:
|`config.h` Override |Default|
|---------------------|-------|
|`I2C1_TIMINGR_PRESC` |`0U` |
|`I2C1_TIMINGR_SCLDEL`|`7U` |
|`I2C1_TIMINGR_SDADEL`|`0U` |
|`I2C1_TIMINGR_SCLH` |`38U` |
|`I2C1_TIMINGR_SCLL` |`129U` |
| Variable | Default |
|-----------------------|---------|
| `I2C1_TIMINGR_PRESC` | `15U` |
| `I2C1_TIMINGR_SCLDEL` | `4U` |
| `I2C1_TIMINGR_SDADEL` | `2U` |
| `I2C1_TIMINGR_SCLH` | `15U` |
| `I2C1_TIMINGR_SCLL` | `21U` |
## Functions :id=functions
STM32 MCUs allow for different "alternate function" modes when configuring GPIO pins. These are required to switch the pins used to I2Cv2 mode. See the respective datasheet for the appropriate values for your MCU.
### `void i2c_init(void)`
| Variable | Default |
|---------------------|---------|
| `I2C1_SCL_PAL_MODE` | `4` |
| `I2C1_SDA_PAL_MODE` | `4` |
Initialize the I2C driver. This function must be called only once, before any of the below functions can be called.
#### Other :id=other
You can also overload the `void i2c_init(void)` function, which has a weak attribute. If you do this the configuration variables above will not be used. Please consult the datasheet of your MCU for the available GPIO configurations. The following is an example initialization function:
This function is weakly defined, meaning it can be overridden if necessary for your particular use case:
```c
void i2c_init(void)
{
setPinInput(B6); // Try releasing special pins for a short time
setPinInput(B7);
wait_ms(10); // Wait for the release to happen
palSetPadMode(GPIOB, 6, PAL_MODE_ALTERNATE(4) | PAL_STM32_OTYPE_OPENDRAIN | PAL_STM32_PUPDR_PULLUP); // Set B6 to I2C function
palSetPadMode(GPIOB, 7, PAL_MODE_ALTERNATE(4) | PAL_STM32_OTYPE_OPENDRAIN | PAL_STM32_PUPDR_PULLUP); // Set B7 to I2C function
void i2c_init(void) {
setPinInput(B6); // Try releasing special pins for a short time
setPinInput(B7);
wait_ms(10); // Wait for the release to happen
palSetPadMode(GPIOB, 6, PAL_MODE_ALTERNATE(4) | PAL_STM32_OTYPE_OPENDRAIN | PAL_STM32_PUPDR_PULLUP); // Set B6 to I2C function
palSetPadMode(GPIOB, 7, PAL_MODE_ALTERNATE(4) | PAL_STM32_OTYPE_OPENDRAIN | PAL_STM32_PUPDR_PULLUP); // Set B7 to I2C function
@ -8,7 +8,7 @@ No special setup is required - just connect the `SS`, `SCK`, `MOSI` and `MISO` p
|MCU |`SS`|`SCK`|`MOSI`|`MISO`|
|---------------|----|-----|------|------|
|ATMega16/32U2/4|`B0`|`B1` |`B2` |`B3` |
|ATmega16/32U2/4|`B0`|`B1` |`B2` |`B3` |
|AT90USB64/128 |`B0`|`B1` |`B2` |`B3` |
|ATmega32A |`B4`|`B7` |`B5` |`B6` |
|ATmega328/P |`B2`|`B5` |`B3` |`B4` |
@ -20,22 +20,34 @@ You may use more than one slave select pin, not just the `SS` pin. This is usefu
You'll need to determine which pins can be used for SPI -- as an example, STM32 parts generally have multiple SPI peripherals, labeled SPI1, SPI2, SPI3 etc.
To enable SPI, modify your board's `halconf.h` to enable SPI - both `HAL_USE_SPI` and `SPI_USE_WAIT` should be `TRUE`, and `SPI_SELECT_MODE` should be `SPI_SELECT_MODE_PAD`.
Then, modify your board's `mcuconf.h` to enable the SPI peripheral you've chosen -- in the case of using SPI2, modify `STM32_SPI_USE_SPI2` to be `TRUE`.
To enable SPI, modify your board's `halconf.h` to enable SPI:
As per the AVR configuration, you may select any other standard GPIO as a slave select pin, and can be supplied to `spi_start()`.
```c
#define HAL_USE_SPI TRUE
#define SPI_USE_WAIT TRUE
#define SPI_SELECT_MODE SPI_SELECT_MODE_PAD
```
Then, modify your board's `mcuconf.h` to enable the peripheral you've chosen, for example:
```c
#undef STM32_SPI_USE_SPI2
#define STM32_SPI_USE_SPI2 TRUE
```
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.
Ryan
3 years ago
GitHub