Skip to content

Home

Jump to bottom Edit New page
Jacek Wieczorek edited this page Apr 5, 2017 · 17 revisions

avr-ds18b20

The MIT License Travis CI

This is detailed description of avr-ds18b20 library. If you have any questions feel free to email me.

1-Wire

1-Wire library consists of three functions:

  • onewireInit( ... ) - initiates 1-Wire bus (sends reset inpulse)
  • onewireRead( ... ) - reads single byte from 1-Wire bus
  • onewireWrite( ... ) - writes single byte to 1-Wire bus

Each of those functions takes arguments such as:

  • port output register address (e.g. &PORTA or &PORTC)
  • port direction register address (e.g. &DDRC or &DDRD)
  • port input register address (e.g. &PINC or &PINB)
  • a bit mask (e.g. ( 1 << 5 ) when sensors is connected to the pin 5)

and in case of onewireWrite an uint8_t value to be sent.

Additionally, onewireInit function returns an error code, which can be one of those values:

Value Macro Description
0 ONEWIRE_ERROR_OK No error occurred
1 ONEWIRE_ERROR_COMM Communication error occurred

Functions described above disable global interrupts when they are called, but SREG value is restored before they exit.

DS18B20

avr-ds18b20 library contains following functions:

  • ds18b20convert( ... ) - requests temperature conversion on selected sensor
  • ds18b20read( ... ) - reads temperature from sensors (obtained during last conversion)
  • ds18b20rom( ... ) - reads ROM address of the sensor
  • ds18b20rsp( ... ) - reads sensor's scratchpad contents
  • ds18b20wsp( ... ) - writes configuration bytes in sensor's scratchpad
  • ds18b20csp( ... ) - copies sensor's configuration into its EEPROM

ds18b20convert( port, direction, portin, mask, rom )

Description: requests temperature conversion on selected sensor. Conversion duration may vary, depending on sensor's precision. Please take look at datasheet.

Argument Description
volatile uint8_t *port Port output register address
volatile uint8_t *direction Port direction register address
volatile uint8_t *portin Port input register address
uint8_t mask Bit mask (describes on which pin sensor is connected)
uint8_t *rom ROM address (NULL if you want to skip matching)

ds18b20read( port, direction, portin, mask, rom, temperature )

Description: reads temperature data from sensor into an int16_t variable. Returned value is actual temperature multiplied by 16 (DS18B20_MUL value)

Argument Description
volatile uint8_t *port Port output register address
volatile uint8_t *direction Port direction register address
volatile uint8_t *portin Port input register address
uint8_t mask Bit mask (describes on which pin sensor is connected)
uint8_t *rom ROM address (NULL if you want to skip matching)
int16_t *temperature Temperature data is going to be stored in the variable under this address

ds18b20rom( port, direction, portin, mask, rom )

Description: reads rom address into array.

Argument Description
volatile uint8_t *port Port output register address
volatile uint8_t *direction Port direction register address
volatile uint8_t *portin Port input register address
uint8_t mask Bit mask (describes on which pin sensor is connected)
uint8_t *rom ROM address is going to be stored here (8b)

ds18b20rsp( port, direction, portin, mask, rom, sp )

Description: reads sensor's scratchpad content into array.

Argument Description
volatile uint8_t *port Port output register address
volatile uint8_t *direction Port direction register address
volatile uint8_t *portin Port input register address
uint8_t mask Bit mask (describes on which pin sensor is connected)
uint8_t *rom ROM address (NULL if you want to skip matching)
uint8_t *sp Scratchpad content is going to be stored here (9b)

ds18b20wsp( port, direction, portin, mask, rom, tl, th, conf )

Description: writes configuration bytes in sensor's scratchpad. Sensor's precision can be set this way.

Argument Description
volatile uint8_t *port Port output register address
volatile uint8_t *direction Port direction register address
volatile uint8_t *portin Port input register address
uint8_t mask Bit mask (describes on which pin sensor is connected)
uint8_t *rom ROM address (NULL if you want to skip matching)
uint8_t tl Thermostat low temperature
uint8_t th Thermostat hight temperature
uint8_t conf Configuration data

To set precision, pass those macros as the last argument:

  • DS18B20_RES09 - 9 bits
  • DS18B20_RES10 - 10 bits
  • DS18B20_RES11 - 11 bits
  • DS18B20_RES12 - 12 bits

ds18b20csp( port, direction, portin, mask, rom )

Description: copies sensor's configuration into its EEPROM in order to make it persistent between power-up cycles. This is rather long process and it takes around 10ms.

Argument Description
volatile uint8_t *port Port output register address
volatile uint8_t *direction Port direction register address
volatile uint8_t *portin Port input register address
uint8_t mask Bit mask (describes on which pin sensor is connected)
uint8_t *rom ROM address (NULL if you want to skip matching)

Every function described above also returns an error code. Those are possible values:

Value Macro Description
0 DS18B20_ERROR_OK No error occurred
1 DS18B20_ERROR_COMM Communication error occurred
2 DS18B20_ERROR_CRC Received data is invalid
3 DS18B20_ERROR_PULL Only zero's were received. This is most likely an issue with pull-up resistor on 1-Wire bus
4 DS18B20_ERROR_OTHER Some other error occurred. For example, user tried to read ROM with ds18b20rom into NULL pointer
Add a custom footer
Add a custom sidebar
Clone this wiki locally