OneWire API

OneWire driver optimized for GSM module.

Header File

Source: include/driver/onewire.h

#include <driver/onewire.h>

Functions

int OneWire(uint8_t pin)

Register OneWire bus

Parameters

pin – [in] IO pin number gpioname_e

Returns

On success, returns handle to OneWire Bus object. 0 on error (no memory)

uint8_t ow_reset(int handle)

Perform a 1-Wire reset cycle. Returns 1 if a device responds with a presence pulse. Returns 0 if there is no device or the bus is shorted or otherwise held low for more than 250uS

Parameters

handle – [in] OneWire bus handle

Returns

void ow_select(int handle, const uint8_t rom[8])

Issue a 1-Wire ROM select command (0x55), you do the reset first.

Parameters

  • handle – [in] OneWire bus handle

  • rom – [in] ROM address to select

void ow_skip(int handle)

Issue a 1-Wire ROM skip command (0xCC), to address all on bus.

Parameters

handle – [in] OneWire bus handle

void ow_write(int handle, uint8_t val, uint8_t power)

Write a byte. If ‘power’ is one then the wire is held high at the end for parasitically powered devices. You are responsible for eventually depowering it by calling ow_depower() or doing another read or write.

Parameters

  • handle – [in] OneWire bus handle

  • val – [in] Input byte

  • power – [in] Power state after write

void ow_write_bytes(int handle, const uint8_t *buf, uint16_t count, uint8_t power)

Write multiple bytes on OneWire bus

See also

ow_write()

Parameters

  • handle – [in] OneWire bus handle

  • buf – [in] Buffer containing data to send

  • count – [in] Length of data in buffer

  • power – [in] Power state after write

uint8_t ow_read(int handle)

Read one byte from OneWire

Parameters

handle – [in] OneWire bus handle

Returns

Read byte

void ow_read_bytes(int handle, uint8_t *buf, uint16_t count)

Read multiple bytes from OneWire bus

Parameters

  • handle – [in] OneWire bus handle

  • buf – [out] Buffer to store data

  • count – [in] length of data to read

void ow_write_bit(int handle, uint8_t v)

Write one bit on bus. The bus is always left powered at the end

See also

ow_write

Parameters

  • handle – [in] OneWire bus handle

  • v – [in] Bit value

uint8_t ow_read_bit(int handle)

Read one bit from bus

Parameters

handle – [in] OneWire bus handle

Returns

Bit value read

void ow_depower(int handle)

Stop forcing power onto the bus. You only need to do this if you used the ‘power’ flag to ow_write() or used a ow_write_bit() call and aren’t about to do another read or write. You would rather not leave this powered if you don’t have to, just in case someone shorts your bus.

Parameters

handle – [in] OneWire bus handle

void ow_reset_search(int handle)

Clear the search state so that if will start from the beginning again.

Parameters

handle – [in] OneWire bus handle

void ow_target_search(int handle, uint8_t family_code)

Setup the search to find the device type ‘family_code’ on the next call to search(*newAddr) if it is present.

Parameters

  • handle – [in] OneWire bus handle

  • family_code – [in] Family code to search

uint8_t ow_search(int handle, uint8_t *newAddr)

Perform a Normal search on OneWire bus (0xF0) Look for the next device. Returns 1 if a new address has been returned. A zero might mean that the bus is shorted, there are no devices, or you have already retrieved all of them. It might be a good idea to check the CRC to make sure you didn’t get garbage. The order is deterministic. You will always get the same devices in the same order.

Parameters

  • handle – [in] OneWire bus handle

  • newAddr – [out] Buffer to store address of newly found device

Returns

returns true if new address found, false if not found

uint8_t ow_search_cond(int handle, uint8_t *newAddr)

Perform a conditional search on OneWire bus (0xEC)

See also

ow_search

Parameters

  • handle – [in] OneWire bus handle

  • newAddr – [out] Buffer to store address of newly found device

Returns

returns true if new address found, false if not found

uint8_t ow_crc8(const uint8_t *addr, uint8_t len)

Compute a Dallas Semiconductor 8 bit CRC, these are used in the ROM and scratchpad registers.

Parameters

  • addr – [in] Input buffer to calculate CRC on

  • len – [in] Length of input data

Returns

CRC value

uint8_t ow_check_crc16(const uint8_t *input, uint16_t len, const uint8_t *inverted_crc, uint16_t crc)

Compute the 1-Wire CRC16 and compare it against the received CRC.

Example usage (reading a DS2408):

// Put everything in a buffer so we can compute the CRC easily. uint8_t buf[13]; buf[0] = 0xF0; // Read PIO Registers buf[1] = 0x88; // LSB address buf[2] = 0x00; // MSB address ow_write_bytes(handle, net, buf, 3); // Write 3 cmd bytes ow_read_bytes(handle net, buf+3, 10); // Read 6 data bytes, 2 0xFF, 2 CRC16 if (!ow_check_crc16(buf, 11, &buf[11])) { // Handle error. }

Parameters

  • input – [in] Array of bytes to checksum.

  • len – [in] How many bytes to use.

  • inverted_crc – [out] The two CRC16 bytes in the received data. This should just point into the received data, not at a 16-bit integer.

  • crc – [in] The crc starting value (0 if not used)

Returns

True, if the CRC matches.

uint16_t ow_crc16(const uint8_t *input, uint16_t len, uint16_t crc)

Compute a Dallas Semiconductor 16 bit CRC. This is required to check the integrity of data received from many 1-Wire devices. Note that the CRC computed here is not what you’ll get from the 1-Wire network, for two reasons: 1) The CRC is transmitted bitwise inverted. 2) Depending on the endian-ness of your processor, the binary representation of the two-byte return value may have a different byte order than the two bytes you get from 1-Wire.

Parameters

  • input – [in] Array of bytes to checksum.

  • len – [in] How many bytes to use.

  • crc – [in] The crc starting value (0 if not used)

Returns

The CRC16, as defined by Dallas Semiconductor.

Macros

OW_ADDR_LEN