Documentation/drivers/analog/adc/ads1115: Add documentation for the Texas Instrument ADS1115 driver
This commit adds the documentation for the Texas Instruments ADS1115 Driver. Signed-off-by: Tony Lin <99093620+justapotato213@users.noreply.github.com>
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Tony Lin
Alin Jerpelea
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==========
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TI ADS1115
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==========
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Contributed by Jia Lin
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The ADS1115 is a 16-bit, 4-channel ADC made by Texas Instruments which operates over
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I2C. It can measure voltages from each channel individually, or between different
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pairs of channels. The ADS1115 also supports a programmable gain amplifier (PGA) and
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a digital comparator.
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.. list-table:: Channel Numbers and Corresponding Sources
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:widths: auto
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* - Channel number
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- AINP
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- AINN
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* - 0
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- AIN0
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- AIN1
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* - 1
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- AIN0
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- AIN3
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* - 2
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- AIN1
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- AIN3
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* - 3
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- AIN2
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- AIN3
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* - 4
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- AIN0
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- GND
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* - 5
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- AIN1
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- GND
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* - 6
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- AIN2
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- GND
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* - 7
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- AIN3
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- GND
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Driver Interface
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---------------------
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To register the ADS1115 device driver as a standard NuttX analog device on your
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board, you can use something similar to the below code for the RP2040.
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.. code-block:: c
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#include <nuttx/analog/ads1115.h>
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#include <nuttx/analog/adc.h>
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/* Register ADS1115 ADC. */
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struct adc_dev_s *ads1115 = ads1115_initialize(rp2040_i2cbus_initialize(0),
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CONFIG_ADC_ADS1115_ADDR);
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if (ads1115 == NULL)
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{
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syslog(LOG_ERR, "Failed to initialize ADS1115\n");
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}
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ret = adc_register("/dev/adc1", ads1115);
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if (ret < 0)
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{
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syslog(LOG_ERR, "Failed to register ADS1115 device driver: %d\n", ret);
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}
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If you have a measurement from the ADS1115, you can convert it into a voltage
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like so:
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.. code-block:: c
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#define FSR (2.048)
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struct adc_msg_s msg;
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/* Some code here to read the ADC device, you can read the ADC driver docs */
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double voltage = ((double)msg.am_data * FSR) / (32768.0);
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Once registered, this driver can be interacted with using the ADC example
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(:ref:`adc-example`). Be sure to enable the software trigger, since the ADS1115
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driver does not support hardware triggers (interrupts). You can also change the
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number of samples per group up to 8 for all 8 channels of the ADC.
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You may need to increase the `CONFIG_ADC_FIFOSIZE` value to something larger
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than 8 in order to be able to store all the ADC measurements after a measurement
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trigger (i.e 9).
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Configuration
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---------------------
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.. list-table:: Configuration Options
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:widths: auto
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* - Name
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- Description
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* - CONFING_ADC_ADS1115_I2C_FREQUENCY
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- I2C frequency of the ADS1115
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* - CONFIG_ADC_ADS1115_ADDR
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- I2C address of the ADS1115
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* - CONFIG_ADC_ADS1115_CHANNEL
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- Default ADC channel to read
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* - CONFIG_ADC_ADS1115_PGA
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- Gain of the ADS1115
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* - CONFIG_ADC_ADS1115_CONTINOUS
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- Continous mode of the ADS1115
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* - CONFIG_ADC_ADS1115_DR
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- Data rate of the ADS1115
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* - CONFIG_ADC_ADS1115_COMP_MODE
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- Mode of the ADS1115 comparator, traditional or window
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* - CONFIG_ADC_ADS1115_COMP_POL
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- Polarity of the ADS1115 comparator, active high or active low
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* - CONFIG_ADC_ADS1115_COMP_LAT
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- Latching mode of the ADS1115 comparator, traditional or latching
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* - CONFIG_ADC_ADS1115_COMP_QUE
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- Comparator queue of the ADS1115, which changes when the ALRT/RDY pin is asserted.
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* - CONFIG_ADC_ADS1115_HI_THRESH
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- HIGH_THRESH register of the ADS1115
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* - CONFIG_ADC_ADS1115_LO_THRESH
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- LOW_THRESH register of the ADS1115
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.. list-table:: Data Rates
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:widths: auto
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* - Value in Kconfig
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- Data Rate
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* - 0
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- 8 SPS
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* - 1
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- 16 SPS
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* - 2
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- 32 SPS
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* - 3
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- 64 SPS
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* - 4
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- 128 SPS
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* - 5
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- 250 SPS
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* - 6
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- 475 SPS
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* - 7
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- 860 SPS
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.. list-table:: PGA Values
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:widths: auto
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* - Value in Kconfig
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- Full Scale Range (FSR)
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* - 0
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- ±6.144V
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* - 1
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- ±4.096V
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* - 2
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- ±2.048V
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* - 3
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- ±1.024V
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* - 4
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- ±0.512V
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* - 5
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- ±0.256V
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* - 6
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- ±0.256V
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* - 7
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- ±0.256V
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.. list-table:: Comparator Queue Values
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:widths: auto
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* - Value in Kconfig
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- Comparator Queue
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* - 0
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- Assert after one conversion
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* - 1
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- Assert after two conversions
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* - 2
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- Assert after four conversions
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* - 3
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- Disable comparator
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Additional ioctl Commands
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--------------------------------
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There are various additional ioctl() commands that can be used with the ADS1115 driver.
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These mostly allow for changes of configuration in runtime.
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.. c:macro:: ANIOC_ADS1115_SET_PGA
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This command changes the gain of the ADS1115 driver. The argument passed should
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be of type ads1115_pga_e, which corresponds to the gain seen above.
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.. c:macro:: ANIOC_ADS1115_SET_MODE
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This command changes the ADS1115 to operate in continous or single-shot mode.
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.. c:macro:: ANIOC_ADS1115_SET_DR
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This command changes the data rate of the ADS1115 driver. The argument passed should
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be of type ads1115_dr_e, which corresponds to the data rate seen above.
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.. c:macro:: ANIOC_ADS1115_SET_COMP_MODE
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This command changes the ADS1115 to operate in either traditional or window comparator mode.
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.. c:macro:: ANIOC_ADS1115_SET_COMP_POL
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This command changes the ADS1115 to operate in either active high or active low mode.
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.. c:macro:: ANIOC_ADS1115_SET_COMP_LAT
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This command changes the ADS1115 to operate in either traditional or latching comparator mode.
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.. c:macro:: ANOIC_ADS1115_SET_COMP_QUEUE
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This command changes the comparator queue feature of the ADS1115. The argument passed should
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be of type ads1115_comp_queue_e, which corresponds to the comparator queue seen above.
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.. c:macro:: ANOIC_ADS1115_SET_HI_THRESH
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This command changes the HIGH_THRESH register of the ADS1115. The argument passed should be
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of type uint16_t, which corresponds to the HIGH_THRESH register value.
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.. c:macro:: ANOIC_ADS1115_SET_LO_THRESH
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This command changes the LOW_THRESH register of the ADS1115. The argument passed should be
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of type uint16_t, which corresponds to the LOW_THRESH register value.
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