This project demonstrates the components mjd_ads1115 and mjd_tmp36.
The mjd_ads1115 component for the TI ADS1115 Analog-To-Digital-Convertor is used to read the voltage output of the analog temperature sensor.
The mjd_tmp36 component for the TMP36 sensor is used to convert the raw voltage reading of the ADC to the ambient temperature in Degrees Celsius.
The Gain (PGA) of the ADC is set to 2.048V for this project to achieve a higher accuracy of the voltage readings (the default of the mjd_ads1115 component is 4.096V). The 2.048V covers the maximum voltage of the TMP36 sensor of 1.75V for +-125 degrees Celsius (its maximum temperature).
Go to the component directory "components/mjd_tmp36" for more documentation, suggested breakout boards (if relevant), installation and wiring instructions, data sheets, FAQ, photo's, etc.
Go to the component directory "components/mjd_ads1115" for more documentation, suggested breakout boards (if relevant), installation and wiring instructions, data sheets, FAQ, photo's, etc.
The temperature accuracy of this sensor is +-2°C so don't use this sensor if you want to perform accurate temperature measurements.
- A decent ESP development board. I suggest to buy a popular development board with good technical documentation and a significant user base. Examples: Adafruit HUZZAH32, Espressif ESP32-DevKitC, Pycom WiPy, Wemos D32.
- The peripherals that are used in the project. The README of each component contains a section "Shop Products".
- A working installation of the Espressif ESP-IDF V3.2 development framework** (detailed instructions @ http://esp-idf.readthedocs.io/en/latest/get-started/index.html).
mkdir ~/esp
cd ~/esp
git clone -b v3.2 --recursive https://github.com/espressif/esp-idf.git esp-idf-v3.2
- A C language editor or the Eclipse IDE CDT (instructions also @ http://esp-idf.readthedocs.io/en/latest/get-started/index.html).
TMP36 SENSOR PIN LAYOUT:
PIN# PIN NAME Description
---- ---------- -----------
1 VCC Power supply (3.3V for the ESP32)
2 VOUT Analog voltage output (the measurement)
3 GND Ground
WIRING DIAGRAM: ADS1115 - MCU:
ADS1115 PIN MCU PIN#
----------- -------
V VCC VCC 3.3V
G GND GND
SCL GPIO#21
SDA GPIO#17
ADDR --
ALR/RDY GPIOI#16
WIRING DIAGRAM: TMP36 - MCU:
TMP36 PIN# PIN NAME MCU PIN#
---------- -------- -----------
1 VCC GPIO#21
2 VOUT VCC 3.3V
3 GND GND
- Connect a 0.1uF ceramic capacitor (I chose 100uF) between the TMP36's pins VCC and GND. It should be as close as possible to the VCC pin of the sensor.
WIRING DIAGRAM: TMP36#1 - ADS1115:
TMP36#1 PIN# PIN NAME ADS1115 PIN
------------ -------- -----------
2 VOUT A0
Optional:
- Hookup a second TMP36 sensor to the ADS1115 pin A1.
- Hookup a third TMP36 sensor to the ADS1115 pin A2.
Tips when using long cables:
- When using a long cable, e.g. an Ethernet CAT5E cable of 75cm, between the output line of the sensor and the MCU then put a 1K resistor in series with the output line of the sensor. Place the resistor relatively close to the TMP36 sensor's voltage output pin.
Tips when operating in noisy environments:
- Connect a +-2.2uF tantalum capacitor between the TMP36's pins VCC and GND when the
device is operated in the presence of high frequency radiated or conducted noise.
- Run
make menuconfigand modify the GPIO PIN#'s that you want to use in the section "MY PROJECT CONFIGURATION". @tip You can also change the log level in Components->Logging: use level INFO for normal operation, use level DEBUG for more detailed logging and to get insights in what the component is actually doing. - Run
make flash monitorto build and upload the example to your board and connect to its serial terminal.
...
I (349) mjd: *** 19700101000000 Thu Jan 1 00:00:00 1970
I (359) myapp: @tip You can also change the log level to DEBUG for more detailed logging and to get insights in what the component is actually doing.
I (369) myapp: @doc Wait 2 seconds after power-on (start logic analyzer, let peripherals become active, ...)
I (2379) myapp: OK Task has been created, and is running right now
I (2379) myapp: app_main() END
I (2379) gpio: GPIO[13]| InputEn: 0| OutputEn: 1| OpenDrain: 0| Pullup: 0| Pulldown: 0| Intr:0
I (2379) myapp: do mjd_ads1115_init()
I (2399) gpio: GPIO[16]| InputEn: 1| OutputEn: 0| OpenDrain: 0| Pullup: 1| Pulldown: 0| Intr:0
I (2399) mjd_ads1115: ADS1115 Log Device Params (*Read again from registers*):
I (2419) mjd_ads1115: OPSTATUS: 0x1 0b00000001 (1)
I (2419) mjd_ads1115: MUX: 0x4 0b00000100 (4)
I (2419) mjd_ads1115: PGA: 0x2 0b00000010 (2)
I (2419) mjd_ads1115: OPMODE: 0x1 0b00000001 (1)
I (2429) mjd_ads1115: DATARATE: 0x0 0b00000000 (0)
I (2439) mjd_ads1115: COMPARATORMODE: 0x0 0b00000000 (0)
I (2439) mjd_ads1115: COMPARATORPOLARITY: 0x0 0b00000000 (0)
I (2449) mjd_ads1115: LATCHINGCOMPARATOR: 0x0 0b00000000 (0)
I (2449) mjd_ads1115: COMPARATORQUEUE: 0x2 0b00000010 (2)
I (2459) mjd_ads1115: LOWTHRESHOLD: 0x0 0b0000000000000000 (0)
I (2469) mjd_ads1115: HIGHTHRESHOLD: 0xFFFF 0b1111111111111111 (65535)
I (2479) mjd_ads1115: CONVERSIONREADYPININLOWREG: 0x0 0b00000000 (0)
I (2479) mjd_ads1115: CONVERSIONREADYPININLOWREG: 0x1 0b00000001 (1)
I (2609) mjd_tmp36: TMP36 Analog Temperature Sensor: config:
I (2619) mjd_tmp36: _offset_volts: 0.500000
I (2619) mjd_tmp36: _scale_degrees_celsius_per_volt: 0.010000
I (2629) mjd: *** DATETIME 19700101000002 Thu Jan 1 00:00:02 1970
I (2639) myapp: TMP36 Measurements via the ADS1115 ADC
I (2639) myapp: LOOP: NBR_OF_RUNS 100000
I (2649) myapp: ***Measurement#1
I (2779) myapp: A0 TMP36: 22.665 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11626 | volt_value (float): 0.727
I (2909) myapp: A1 TMP36: 22.952 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11672 | volt_value (float): 0.730
I (3039) myapp: A2 TMP36: 22.652 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11624 | volt_value (float): 0.727
I (5039) myapp: ***Measurement#2
I (5169) myapp: A0 TMP36: 22.671 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11627 | volt_value (float): 0.727
I (5299) myapp: A1 TMP36: 22.940 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11670 | volt_value (float): 0.729
I (5429) myapp: A2 TMP36: 22.652 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11624 | volt_value (float): 0.727
I (7429) myapp: ***Measurement#3
I (7559) myapp: A0 TMP36: 22.665 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11626 | volt_value (float): 0.727
I (7689) myapp: A1 TMP36: 22.940 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11670 | volt_value (float): 0.729
I (7819) myapp: A2 TMP36: 22.646 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11623 | volt_value (float): 0.726
I (9819) myapp: ***Measurement#4
I (9949) myapp: A0 TMP36: 22.665 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11626 | volt_value (float): 0.727
I (10079) myapp: A1 TMP36: 22.933 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11669 | volt_value (float): 0.729
I (10209) myapp: A2 TMP36: 22.621 Degrees Celsius | ADC Pin A0: raw_value (s int16): 11619 | volt_value (float): 0.726
...
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