/*! LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution. LTC2442: 24-Bit, 4-Channel Delta Sigma ADC with Integrated Amplifier LTC2448: 24-Bit, 8-/16-Channel Delta Sigma ADCs with Selectable Speed/Resolution @verbatim The LTC2444/LTC2445/LTC2448/LTC2449 are 8-/16-channel (4-/8-differential) high speed 24-bit No Latency Delta Sigma ADCs. They use a proprietary delta-sigma architecture enabling variable speed/resolution. Through a simple 4-wire serial interface, ten speed/resolution combinations 6.9Hz/280nVRMS to 3.5kHz/25uVRMS (4kHz with external oscillator) can be selected with no latency between conversion results or shift in DC accuracy (offset, full-scale, linearity, drift). Additionally, a 2X speed mode can be selected enabling output rates up to 7kHz (8kHz if an external oscillator is used) with one cycle latency. @endverbatim http://www.linear.com/product/LTC2449 http://www.linear.com/product/LTC2442 http://www.linear.com/product/LTC2448 http://www.linear.com/product/LTC2449#demoboards http://www.linear.com/product/LTC2442#demoboards http://www.linear.com/product/LTC2448#demoboards Copyright 2018(c) Analog Devices, Inc. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. - Neither the name of Analog Devices, Inc. nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. - The use of this software may or may not infringe the patent rights of one or more patent holders. This license does not release you from the requirement that you obtain separate licenses from these patent holders to use this software. - Use of the software either in source or binary form, must be run on or directly connected to an Analog Devices Inc. component. THIS SOFTWARE IS PROVIDED BY ANALOG DEVICES "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ANALOG DEVICES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, INTELLECTUAL PROPERTY RIGHTS, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ //! @ingroup Analog_to_Digital_Converters //! @{ //! @defgroup LTC2449 LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution //! @} /*! @file @ingroup LTC2449 Library for LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution */ #include #include #include "Linduino.h" #include "LT_SPI.h" #include "LTC2449.h" #include //! Define the SPI CS pin #ifndef LTC2449_CS #define LTC2449_CS QUIKEVAL_CS #endif int8_t LTC2449_EOC_timeout(uint8_t cs, uint16_t miso_timeout) // Checks for EOC with a specified timeout (ms) { uint16_t timer_count = 0; // Timer count for MISO output_low(cs); //! 1) Pull CS low while (1) //! 2) Wait for SDO (MISO) to go low { if (input(MISO) == 0) break; //! 3) If SDO is low, break loop if (timer_count++>miso_timeout) // If timeout, return 1 (failure) { output_high(cs); // Pull CS high return(1); } else delay(1); } output_high(cs); // Pull CS high return(0); } // Reads from LTC2449. void LTC2449_read(uint8_t cs, uint16_t adc_command, uint32_t *adc_code) { LT_union_int32_4bytes data, command; // LTC2449 data and command LT_union_int16_2bytes temp_comm; temp_comm.LT_int16 = adc_command; command.LT_byte[3] = temp_comm.LT_byte[1]; command.LT_byte[2] = temp_comm.LT_byte[0]; command.LT_byte[1] = 0; command.LT_byte[0] = 0; output_low(cs); //! 1) Pull CS low spi_transfer_block(cs, command.LT_byte, data.LT_byte, (uint8_t)4); //! 2) Transfer arrays output_high(cs); //! 3) Pull CS high *adc_code = data.LT_int32; } // Calculates the voltage corresponding to an adc code, given lsb weight (in volts) and the calibrated // adc offset code (zero code that is subtracted from adc_code). float LTC2449_code_to_voltage(int32_t adc_code, float LTC2449_lsb, int32_t LTC2449_offset_code) { float adc_voltage; adc_code -= 536870912; //! 1) Converts offset binary to binary adc_voltage=(float)(adc_code+LTC2449_offset_code)*LTC2449_lsb; //! 2) Calculate voltage from ADC code, lsb, offset. return(adc_voltage); } // Calculate the lsb weight and offset code given a full-scale code and a measured zero-code. void LTC2449_cal_voltage(int32_t zero_code, int32_t fs_code, float zero_voltage, float fs_voltage, float *LTC2449_lsb, int32_t *LTC2449_offset_code) { zero_code -= 536870912; //! 1) Converts zero code from offset binary to binary fs_code -= 536870912; //! 2) Converts full scale code from offset binary to binary float temp_offset; *LTC2449_lsb = (fs_voltage-zero_voltage)/((float)(fs_code - zero_code)); //! 3) Calculate the LSB temp_offset = (zero_voltage/ *LTC2449_lsb) - zero_code; //! 4) Calculate Unipolar offset temp_offset = (temp_offset > (floor(temp_offset) + 0.5)) ? ceil(temp_offset) : floor(temp_offset); //! 5) Round *LTC2449_offset_code = (int32_t)temp_offset; //! 6) Cast as int32_t }