/*! 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. SPI DATA FORMAT (MSB First): Byte #1 Byte #2 Data Out : !EOC DMY SIG D28 D27 D26 D25 D24 D23 D22 D21 D20 D19 D18 D17 D16 Data In : 1 0 EN SGL OS S2 S1 S0 OSR3 OSR2 OSR1 OSR1 SPD X X X Byte #3 Byte #4 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 *D3 *D2 *D1 *D0 X X X X X X X X X X X X X X X X !EOC : End of Conversion Bit (Active Low) DMY : Dummy Bit (Always 0) SIG : Sign Bit (1-data positive, 0-data negative) Dx : Data Bits *Dx : Data Bits Below lsb EN : Enable Bit (0-keep previous mode, 1-change mode) SGL : Enable Single-Ended Bit (0-differential, 1-single-ended) OS : ODD/Sign Bit Sx : Address Select Bit 0SRX : Over Sampling Rate Bits SPD : Double Output Rate Select Bit (0-Normal rate, auto-calibration on, 2x rate, auto_calibration off) Command Byte #1 1 0 EN SGL OS S2 S1 S0 Comments 1 0 0 X X X X X Keep Previous Mode 1 0 1 0 X X X X Differential Mode 1 0 1 1 X X X X Single-Ended Mode | Coversion Rate | RMS | ENOB | OSR | Latency Command Byte #2 |Internal | External | Noise | | | | 9MHz | 10.24MHz | | | | OSR3 OSR2 OSR1 OSR1 SPD | Clock | Clock | | | | 0 0 0 0 0 Keep Previous Speed/Resolution 0 0 0 1 0 3.52kHz 4kHz 23uV 17 64 none 0 0 1 0 0 1.76kHz 2kHz 3.5uV 20.1 128 none 0 0 1 1 0 880Hz 1kHz 2uV 21.3 256 none 0 1 0 0 0 440Hz 500Hz 1.4uV 21.8 512 none 0 1 0 1 0 220Hz 250Hz 1uV 22.4 1024 none 0 1 1 0 0 110Hz 125Hz 750nV 22.9 2048 none 0 1 1 1 0 55Hz 62.5Hz 510nV 23.4 4096 none 1 0 0 0 0 27.5Hz 31.25Hz 375nV 24 8192 none 1 0 0 1 0 13.75Hz 15.625Hz 250nV 24.4 16384 none 1 1 1 1 0 6.87kHz 7.8125Hz 200nV 24.6 32768 none 0 0 0 0 1 Keep Previous Speed/Resolution OSR3 OSR2 OSR1 OSR1 1 2X Mode *all clock speeds double Example Code: Read Channel 0 in Single-Ended with OSR of 65536 uint16_t miso_timeout = 1000; adc_command = LTC2449_CH0 | LTC2449_OSR_32768 | LTC2449_SPEED_2X; // Build ADC command for channel 0 // OSR = 32768*2 = 65536 if(LTC2449_EOC_timeout(LTC2449_CS, miso_timeout)) // Check for EOC return; // Exit if timeout is reached LTC2449_read(LTC2449_CS, adc_command, &adc_code); // Throws out last reading if(LTC2449_EOC_timeout(LTC2449_CS, miso_timeout)) // Check for EOC return; // Exit if timeout is reached LTC2449_read(LTC2449_CS, adc_command, &adc_code); // Obtains the current reading and stores to adc_code variable // Convert adc_code to voltage adc_voltage = LTC2449_code_to_voltage(adc_code, LTC2449_lsb, LTC2449_offset_code); @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. */ /*! @file @ingroup LTC2449 Header for LTC2449: 24-Bit, 16-Channel Delta Sigma ADCs with Selectable Speed/Resolution */ #ifndef LTC2449_H #define LTC2449_H //! Define the SPI CS pin #ifndef LTC2449_CS #define LTC2449_CS QUIKEVAL_CS #endif /*! @name Mode Configuration @{ */ #define LTC2449_KEEP_PREVIOUS_MODE 0x8000 #define LTC2449_KEEP_PREVIOUS_SPEED_RESOLUTION 0x0000 #define LTC2449_SPEED_1X 0x0000 #define LTC2449_SPEED_2X 0x0008 /*! @} */ /*! @name Single-Ended Channels Configuration @{ */ #define LTC2449_CH0 0xB000 #define LTC2449_CH1 0xB800 #define LTC2449_CH2 0xB100 #define LTC2449_CH3 0xB900 #define LTC2449_CH4 0xB200 #define LTC2449_CH5 0xBA00 #define LTC2449_CH6 0xB300 #define LTC2449_CH7 0xBB00 #define LTC2449_CH8 0xB400 #define LTC2449_CH9 0xBC00 #define LTC2449_CH10 0xB500 #define LTC2449_CH11 0xBD00 #define LTC2449_CH12 0xB600 #define LTC2449_CH13 0xBE00 #define LTC2449_CH14 0xB700 #define LTC2449_CH15 0xBF00 /*! @} */ /*! @name Differential Channel Configuration @{ */ #define LTC2449_P0_N1 0xA000 #define LTC2449_P1_N0 0xA800 #define LTC2449_P2_N3 0xA100 #define LTC2449_P3_N2 0xA900 #define LTC2449_P4_N5 0xA200 #define LTC2449_P5_N4 0xAA00 #define LTC2449_P6_N7 0xA300 #define LTC2449_P7_N6 0xAB00 #define LTC2449_P8_N9 0xA400 #define LTC2449_P9_N8 0xAC00 #define LTC2449_P10_N11 0xA500 #define LTC2449_P11_N10 0xAD00 #define LTC2449_P12_N13 0xA600 #define LTC2449_P13_N12 0xAE00 #define LTC2449_P14_N15 0xA700 #define LTC2449_P15_N14 0xAF00 /*! @} */ /*Commands Construct a channel / resolution control word by bitwise ORing one choice from the channel configuration and one choice from the Oversample ratio configuration. You can also enable 2Xmode, which will increase sample rate by a factor of 2 but introduce one cycle of latency. Example - read channel 3 single-ended at OSR2048, with 2X mode enabled. adc_command = (LTC2449_CH3 | LTC2449_OSR_2048) | LTC2449_SPEED_2X; */ /*! @name Oversample Ratio (OSR) Commands @{ */ #define LTC2449_OSR_64 0xA010 #define LTC2449_OSR_128 0xA020 #define LTC2449_OSR_256 0xA030 #define LTC2449_OSR_512 0xA040 #define LTC2449_OSR_1024 0xA050 #define LTC2449_OSR_2048 0xA060 #define LTC2449_OSR_4096 0xA070 #define LTC2449_OSR_8192 0xA080 #define LTC2449_OSR_16384 0xA090 #define LTC2449_OSR_32768 0xA0F0 /*! @}*/ //! Checks for EOC with a specified timeout //! @return Returns 0=successful, 1=unsuccessful (exceeded timeout) int8_t LTC2449_EOC_timeout(uint8_t cs, //!< Chip Select pin uint16_t miso_timeout //!< Timeout (in milliseconds) ); //! Reads from LTC2449. //! @return void void LTC2449_read(uint8_t cs, //!< Chip Select pin uint16_t adc_command, //!< 2 byte command written to LTC2449 uint32_t *adc_code //!< 4 byte conversion code read from LTC2449 ); //! 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). //! @return Returns voltage calculated from ADC code. float LTC2449_code_to_voltage(int32_t adc_code, //!< Code read from adc float LTC2449_lsb, //!< LSB weight (in volts) int32_t LTC2449_offset_code //!< The calibrated offset code (This is the adc code zero code that will be subtraced from adc_code) ); //! Calculate the lsb weight and offset code given a full-scale code and a measured zero-code. //! @return Void void LTC2449_cal_voltage(int32_t zero_code, //!< Measured code with the inputs shorted to ground int32_t fs_code, //!< Measured code at nearly full-scale float zero_voltage, //!< Measured zero voltage float fs_voltage, //!< Voltage measured at input (with voltmeter) when fs_code was read from adc float *LTC2449_lsb, //!< Overwritten with lsb weight (in volts) int32_t *LTC2449_offset_code //!< Overwritten with offset code (zero code) ); #endif // LTC2449_H