ESE 350 Microcontroller Laboratory Lab 5: Sensor-Actuator Lab

Transcription

1 ESE 350 Microcontroller Laboratory Lab 5: Sensor-Actuator Lab The purpose of this lab is to learn about sensors and use the ADC module to digitize the sensor signals. You will use the digitized signals for actuation. You will work with audio, temperature, motion and light sensors and use them to trigger motors, speakers and lights. In the first part of the lab you will accomplish this using the HCS12 microcontroller and ADC to sense and actuate. In the second part you will see how easy it is to do the sensing on the FireFly node using the nano-rk RTOS. The hardware of this lab consists of a firefly sensor expansion board and the FireFly node. All documentation is on the nano-rk website. More information about the sensor board can be found on: Light sensor Audio sensor Temperature sensor 3-axis accelerometer Fig 1: Sensor Expansion board

2 Fig 2: Pinout of Sensor Expansion Board 1. The step 1 of the lab consists of connecting the sensor expansion board and observing analog output from all the sensors. For the pin-out of the sensor expansion board please look at Fig 2. As you can see that the header on the sensor expansion board is not wide enough to mount directly on the breadboard. In order to connect this to the breadboard we use a minor tweak. We first connect the sensor board to the ribbon connector and then to the breadboard as shown in Fig 3 Fig 3: Connecting sensor expansion board to bread board Please note that in order to power the board you must connect pin 1 to 3.3V and pin 9 (Power Control-F7) and pin 10 to GND.

3 2. We are going to look at the signals coming out of the accelerometer, light sensor and audio sensor. Accelerometer (ADXL): The accelerometer on the sensor expansion board is the chip in the center of the board. Analog Devices Inc manufactures it as part number ADXL330KCPZ-RL. Connect only two channels of the Oscilloscope to the Xout (F2) and Yout (F5). Adjust the voltage to 1V/div and time to 1sec/div so that you can look at the change in the signals as you move the sensor expansion board. Note down the range of the signal and also print out a copy to get it signed off by a TA at the end of the lab. Photodiode: The light sensor (photocell) on the expansion board is on the bottom right corner with red and white stripes. Advanced Photonix Inc. manufactures it as part number PDV-P9003. Connect one channel of the Oscilloscope to the pin light (F1). Adjust the voltage to 1V/div and time to 1sec/div so that you can look at the change in the signals as you change the intensity with a photocell with a flashlight. Note down the range of the signal and also print out a copy to get it signed off by a TA at the end of the lab. Audio Sensor: Finally, the audio sensor is the silver and black piece on the top right corner of the sensor expansion board. Knowles Inc. manufactures it as part number MD9745APA-1. Connect one channel of the Oscilloscope to the pin mic (F3). Adjust the voltage to 1V/div and time to 1sec/div so that you can look at the change in the signals as you change as you speak in the microphone. Note down the range of the signal and also print out a copy to get it signed off by a TA at the end of the lab. 3. Accelerometer-controlled Sound Generator: The objective of this part is to change the amplitude of a speaker with variation in the X-axis value of the accelerometer and change the frequency with the change in value along the Y-axis of the accelerometer. To implement this we will connect the output from pin 4 Xout (F2) and pin 7 Yout (F5) to the ports PAD00 and PAD01 of the HC12. Use the ADC at 1MHz with 10-bit resolution. The fastest the ADC can sample in our case is 2Mhz (E-clock)/2 (Minimum prescale) i.e. 1Mhz.The ADC must sequentially obtain the digital value of both the channels. For changing the frequency of the speaker output (i.e. the PWM period), we vary the Y-axis. Change the period using PWMPERx such that the period varies between 800Hz and 2Khz at a constant duty cycle of a 50% by changing the PWMDTYx register. If you wish to use the output compare, that is another option to generate the PWM. Please note that you change the period depending upon the change in the values of the ADC. To change the amplitude we convert the signal to its analog equivalent by using the 3-bit Digital-to-Analog (DAC) board. Power the DAC board at +5V (red) and -5V

4 (yellow). Make sure that there is a common ground between your breakout board and the DAC ground (black). Connect the 3 outputs of the DAC to the I/O channels of HC12. Since it is a 3-bit DAC, you will need to divide the range of ADC value obtained in 8 states. We change digital value 0 or 1 on the three I/O lines depending upon the output state. DAC example: If the ADC value varies between 0-160, then 0-20 is state 0 which corresponds to 000 while is state 4 which corresponds to is state 7 which corresponds to 111. We drive the speaker with a 2N3904 transistor where the collector V cc varies with the output of DAC (to change the amplitude of the signal) and the base is connected to the output of PWM to change the frequency through the speaker, as shown in Fig. 4. Fig 4: Speaker Circuit Please demo your output to a TA. 4. Light-controlled Motor: Next we move on to using the light sensor. As you have noticed in the step 1 that as you shine the light on the photocell the voltage on the Pin 3(F1) decreases. Update your code to use the 3 rd A/D channel and look at the variation of the digitized values of the photocell. Initialize another channel of PWM and set it so that the period of the PWM is 20ms. Then change the PWMDTYx register depending upon the value of the ADC so that so that the duty cycle increases as we shine light on the photocell. Verify the waveform on an oscilloscope. Use the setup as lab 4 with the H-Bridge and connect a DC motor to the PWM pin. You will notice a change in the speed of the motor as you shine light on the photocell. Please demo the output to a TA. 5. Audio-sensor controlled LEDs: Sound Meter The last part of the Part-1 of this lab is to use an audio sensor to implement a clapper which shows the length of sound measured. When you observed the output from pin

5 5(F3) of the sensor expansion board you observed that the voltage at the output of the microphone decreases. Observe the change in the digital values and define a timer overflow interrupt TCNT that keeps a track of time. Connect 8 LED s to 8 I/O ports of HC12 and have the LED s come on depending ON the depending upon the time you continuously talk in the microphone. i.e. for continuously talking for a second one LED comes ON while continuously talking for 8 sec or more all the LED s come on. It s basically an LED indicator for duration of length sound. Once you complete it please demo the output to a TA. Lab 5 Part II: Now the easy way with FireFly and the nano-rk RTOS This part gets you familiarized with the FireFly node and programming in the nano- RK RTOS. We have provided you with most of the skeleton code so you just need to add a line or two for each of these tasks. 1. Download the nano-rk project from BlackBoard. Click on the Cygwin shortcut and cd to the downloaded area. Do not use the nano-rk already installed on the RCA machines unless we send you an that says otherwise. Look in the Projects directory you should find your three tasks there. Read the FireFly datasheet and familiarize yourself with the different components in your kit. 2. Make sure that each of the Firefly nodes are connected to an antenna and a sensor node. Please refer to the datasheet and connect the programmer board to the Firefly. The cables are connected in a particular way. Double-check the two cable connections between the Firefly and the programmer board. Connect the USB cable of the programmer to the computer and switch ON the programmer. 3. Refer to the How-To document posted on the Blackboard to understand how to program a Firefly node. 4. For this particular lab with the Firefly we will go over three small tasks that help you understand the Firefly. At the end of each task please demo the output to a TA and print out the.c file and get it signed by a TA. 5. Task 1 Basic Tasks - Open the basic_tasks folder under projects. (a) Compile the code by typing make in the basic_tasks directory and then download the compile code by typing make program. What do you see and why are the LEDs blinking so? (b) Modify the basic_tasks.c file so that you get a stack overflow error which can be seen on the hyper terminal. Stack overflow explanation along with other errors can be found at the link (c) Comment the stack overflow error. Now write two more tasks under the nrk_create_taskset() function. Write Task3() and Task4() to blink the red, green, blue

6 and orange led at the same rate together and then with at 100ms, 500ms, 1sec and 2.5sec respectively. 6. Task 2 Basic Sensors - Open the basic_sensors folder. When you compile the code you will see that the value of the battery is continuously printed on the hyper terminal. Modify the code basic_sensors.c to print out the values for all the sensors i.e. light, temperature, audio and three axes of the accelerometer. Please refer to the page 7. Task 3 Networked Sensors - Open the folder bmac_sensors. You can see two sub-folders under the bmac_sensors folder for a client and a server. The client sends the value of battery over the radio to the server, which in-turn prints it out on the terminal. The goal of the task is to modify any code that is required on the client and the server in order to transmit and printout all sensor values on the hyper terminal. That s it! Now you are ready to program networks of sensors, controllers and actuators. Think about ways you can use the HCS12 and FireFly for your final projects.