nRF51 SDK: Software controlled TWI Master driver

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Software controlled TWI Master driver
Peripheral Drivers

Software controlled TWI Master driver. More...

## Macros

#define | TWI_READ_BIT (0x01)
| If this bit is set in the address field, transfer direction is from slave to master.
#define | TWI_ISSUE_STOP ((bool)true)
| Parameter for twi_master_transfer.
#define | TWI_DONT_ISSUE_STOP ((bool)false)
| Parameter for twi_master_transfer.
#define | TWI_SCL_HIGH() do { NRF_GPIO->OUTSET = (1UL << TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER); } while(0)
#define | TWI_SCL_LOW() do { NRF_GPIO->OUTCLR = (1UL << TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER); } while(0)
#define | TWI_SDA_HIGH() do { NRF_GPIO->OUTSET = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)
#define | TWI_SDA_LOW() do { NRF_GPIO->OUTCLR = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)
#define | TWI_SDA_INPUT() do { NRF_GPIO->DIRCLR = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)
#define | TWI_SDA_OUTPUT() do { NRF_GPIO->DIRSET = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)
#define | TWI_SCL_OUTPUT() do { NRF_GPIO->DIRSET = (1UL << TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER); } while(0)
#define | TWI_SDA_READ() ((NRF_GPIO->IN >> TWI_MASTER_CONFIG_DATA_PIN_NUMBER) & 0x1UL)
#define | TWI_SCL_READ() ((NRF_GPIO->IN >> TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER) & 0x1UL)
#define | TWI_DELAY() nrf_delay_us(4)

## Functions

bool | twi_master_init (void)
| Function for initializing TWI bus IO pins and checks if the bus is operational. More...
bool | twi_master_transfer (uint8_t address, uint8_t *data, uint8_t data_length, bool issue_stop_condition)
| Function for transferring data over TWI bus. More...

## Detailed Description

Software controlled TWI Master driver.

Supported features:

- Repeated start
- No multi-master
- Only 7-bit addressing
- Supports clock stretching (with optional SMBus style slave timeout)
- Tries to handle slaves stuck in the middle of transfer

## Macro Definition Documentation

#define TWI_DELAY | ( |  | ) | nrf_delay_us(4)

Time to wait when pin states are changed. For fast-mode the delay can be zero and for standard-mode 4 us delay is sufficient.

#define TWI_SCL_HIGH | ( |  | ) | do { NRF_GPIO->OUTSET = (1UL << TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER); } while(0)

Pulls SCL line high

#define TWI_SCL_LOW | ( |  | ) | do { NRF_GPIO->OUTCLR = (1UL << TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER); } while(0)

Pulls SCL line low

#define TWI_SCL_OUTPUT | ( |  | ) | do { NRF_GPIO->DIRSET = (1UL << TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER); } while(0)

Configures SCL pin as output

#define TWI_SCL_READ | ( |  | ) | ((NRF_GPIO->IN >> TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER) & 0x1UL)

Reads current state of SCL

#define TWI_SDA_HIGH | ( |  | ) | do { NRF_GPIO->OUTSET = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)

Pulls SDA line high

#define TWI_SDA_INPUT | ( |  | ) | do { NRF_GPIO->DIRCLR = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)

Configures SDA pin as input

#define TWI_SDA_LOW | ( |  | ) | do { NRF_GPIO->OUTCLR = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)

Pulls SDA line low

#define TWI_SDA_OUTPUT | ( |  | ) | do { NRF_GPIO->DIRSET = (1UL << TWI_MASTER_CONFIG_DATA_PIN_NUMBER); } while(0)

Configures SDA pin as output

#define TWI_SDA_READ | ( |  | ) | ((NRF_GPIO->IN >> TWI_MASTER_CONFIG_DATA_PIN_NUMBER) & 0x1UL)

Reads current state of SDA

## Function Documentation

bool twi_master_init | ( | void |  | ) |

Function for initializing TWI bus IO pins and checks if the bus is operational.

Both pins are configured as Standard-0, No-drive-1 (open drain).

Returns

Return values

  true | TWI bus is clear for transfers.
  false | TWI bus is stuck.

bool twi_master_transfer | ( | uint8_t | address,
|  | uint8_t * | data,
|  | uint8_t | data_length,
|  | bool | issue_stop_condition
| ) |  |

Function for transferring data over TWI bus.

If TWI master detects even one NACK from the slave or timeout occurs, STOP condition is issued and the function returns false. Bit 0 (TWI_READ_BIT) in the address parameter controls transfer direction;

- If 1, master reads data_length number of bytes from the slave
- If 0, master writes data_length number of bytes to the slave.

Note
  Make sure at least data_length number of bytes is allocated in data if TWI_READ_BIT is set.
  TWI_ISSUE_STOP

Parameters

  address | Data transfer direction (LSB) / Slave address (7 MSBs).
  data | Pointer to data.
  data_length | Number of bytes to transfer.
  issue_stop_condition | If TWI_ISSUE_STOP, STOP condition is issued before exiting function. If TWI_DONT_ISSUE_STOP, STOP condition is not issued before exiting function. If transfer failed for any reason, STOP condition will be issued in any case.

Returns

Return values

  true | Data transfer succeeded without errors.
  false | Data transfer failed.