Arduino library for an LTC2991 temperature and voltage control IC.

Experimental - not tested myself, (no hardware)

LTC2991 is an experimental library for the LTC2991 IC which is typically used to monitor temperature and voltage. It also has a PWM out to control e.g. a fan.

The IC supports normal voltage measurement (8 lines), differential voltage measurements (4 pairs) and temperature measurements (4 pairs). These can be combined in a mix. As the IC has only 8 inputs available one has to choose what.

Read the datasheet for the details.

From datasheet - table 1

The address template is 0 1 0 0 - 1 A2 A1 A0 ==> 0x48 if all address pins are grounded,

• https://github.com/RobTillaart/LTC2991
• https://github.com/RobTillaart/temperature converters

#include "LTC2991.h"

• LTC2991(const uint8_t address, TwoWire *wire = Wire) The address is 0x48..0x4F depending on the address pins. The library does not check the range.
• bool begin() UNO ea. initializes the class. Returns true if the LTC2991 address is on the I2C bus.
  Note: do call Wire.begin() before begin()
• bool isConnected() Returns true if the LTC2991 address is on the I2C bus.
• uint8_t getAddress() Returns the address set in the constructor.

• bool new_data(uint8_t channel) true if there is a new external measurement available. This can be a voltage or a temperature measurement.
• bool new_temperature() true if there is a new internal temperature measurement available.
• bool new_voltage() true, if there is a new internal voltage measurement available.
• bool is_busy() true if the sensor is converting...

The following functions work on pairs:

• void trigger_conversion(uint8_t n) wrapper around enable(n, true), better naming.
• void trigger_conversion_all() triggers conversions for all 4 channels/pairs.
• void enable(uint8_t n, bool enable) enable or disable an external line. disable can be used to stop the repeat mode.
• bool is_enabled(uint8_t n) idem
• void enable_filter(uint8_t n, bool enable) enable filter - not investigated.
• bool is_enabled_filter(uint8_t n) idem.
• void set_Kelvin(uint8_t n) sets temperature mode to Kelvin, implicit set_mode_temperature().
• void set_Celsius(uint8_t n) sets temperature mode to Celsius, implicit set_mode_temperature.
• void set_temp_scale(uint8_t n, bool Kelvin = true) used to switch between Kelvin and Celsius.
• char get_temp_scale(uint8_t n) returns 'K' or 'C'.
• void set_mode_temperature(uint8_t n) sets operational mode.
• void set_mode_voltage_differential(uint8_t n) sets operational mode.
• void set_mode_voltage_normal(uint8_t n) sets operational mode.
• uint8_t get_operational_mode(uint8_t n) returns operational mode.
• uint8_t get_differential_mode(uint8_t n) returns differential flag.
• float get_value(uint8_t channel) channel = 1..8; depending on the operational mode it returns the temperature or the (differential) voltage.

• void enable_Tintern_Vcc(bool enable) enable internal temperature measurements.
• bool is_enabled_Tintern_Vcc() idem.
• void enable_filter_Tintern(bool enable) enable filter - not investigated
• bool is_enabled_filter_Tintern()
• void set_Kelvin_Tintern() use Kelvin.
• void set_Celsius_Tintern() use Celsius.
• void set_temp_scale_Tintern(bool Kelvin = true) Obsolete?.
• char get_temp_scale_Tintern() returns 'K' or 'C'.
• float get_Tintern() returns the internal temperature.
• float get_VCC() returns the internal voltage.

• void set_acquisition_repeat() set continuous measurement mode.
• void set_acquisition_single() set single shot mode. Note that before a measurement is made one needs to call trigger_conversion(n) or trigger_conversion_all().
• uint8_t get_acquisition_mode() return mode set (0,1).
  • 1 = repeat
  • 0 = single

• void set_PWM(uint16_t value = 0) value is 0..511.
• void set_PWM_fast(uint16_t value = 0) value is 0..511, less resolution (256 steps).
• uint16_t get_PWM() returns the value from the PWM register, when using PWM_fast this can differ 1.
• void invert_PWM(bool invert) idem.
• bool is_inverted_PWM() idem.
• void enable_PWM(bool enable) idem.
• bool is_enabled_PWM() idem.

No data available yet. To be measured when hardware is available... if you happen to have performance figures, please share them in an issue.

• get hardware to test
• improve documentation (a lot)

• error handling
• unit tests if possible?
• remove magic numbers / masks from code
  • some defines prepared in CPP file => to .h

• cache registers (which) or ?
• cache a number of flags to speed up retrieving data
• optimizations
  • code / math
  • optimize multi-byte read / write
• void disable_PWM() convenience,
• enable_PWM(bool) default true flag
• void LTC2991::enable(uint8_t mask) faster to set multiple.

• redo naming of some functions?
  • first get hands on experience.
• add Fahrenheit
  • do low level in Kelvin and convert to KFC as needed.
  • would simplify get_value
  • need an enum
  • would interface # functions increase too much?
  • == > Users can do this conversion.

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