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learn:courses:microprocessor-io-lab-1b:start [2017/03/15 17:51] – [7.1. Control Registers] Marthalearn:courses:microprocessor-io-lab-1b:start [2022/10/04 11:38] (current) – external edit 127.0.0.1
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-====== Lab 1b: Microprocessor IO ======+====== Lab 1b: Microprocessor I/O ====== 
 +[[{}/learn/courses/microprocessor-io-unit-1/start|Back to Unit 1]] 
 +[[{}/learn/courses/microprocessor-io-lab-1a/start|Back to Lab 1a]]
 == Download This Document == == Download This Document ==
-  * {{ :learn:courses:microprocessor-io-lab-1b:lab_1b.pdf |Lab1b PDF}} +{{ :learn:courses:microprocessor-io-lab-1b:lab_1b.pdf |Lab 1b PDF}}
  
 ===== 1. Objectives ===== ===== 1. Objectives =====
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   - How to write a computer program using the [[http://www.tutorialspoint.com/cprogramming/index.htm|C language]].   - How to write a computer program using the [[http://www.tutorialspoint.com/cprogramming/index.htm|C language]].
   - How to launch a [[http://microchip.wikidot.com/tls0101:design-environment|Microchip MPLAB X]] project.   - How to launch a [[http://microchip.wikidot.com/tls0101:design-environment|Microchip MPLAB X]] project.
-  - How to configure the PIC32 I/O pins for digital input and output (See [[https://reference.digilentinc.com/learn/courses/microprocessor-io-lab-1a/start|Lab 1a]]).+  - How to configure the PIC32 I/O pins for digital input and output (See [[/learn/courses/microprocessor-io-lab-1a/start|Lab 1a]]).
  
  
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 ===== 3. Equipment List ===== ===== 3. Equipment List =====
 ==== 3.1. Hardware ==== ==== 3.1. Hardware ====
-  * [[http://store.digilentinc.com/basys-mx3-pic32mx-trainer-board-recommended-for-embedded-systems-courses/|Basys MX3 trainer board]] +  - [[https://digilent.com/shop/basys-mx3-pic32mx-trainer-board-for-embedded-systems-courses/|Basys MX3 trainer board]] 
-  * [[http://store.digilentinc.com/usb-a-to-micro-b-cable/|Standard USB A to micro-B cable]] +  - [[https://digilent.com/shop/usb-a-to-micro-b-cable/|Standard USB A to micro-B cable]] 
-  * Workstation computer running Windows 10 or higher, MAC OS, or Linux+  - Workstation computer running Windows 10 or higher, MAC OS, or Linux
  
 In addition, we suggest the following instruments: In addition, we suggest the following instruments:
-  * [[http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,1018&Prod=ANALOG-DISCOVERY|Digilent Analog Discovery 2]]+  - [[http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,842,1018&Prod=ANALOG-DISCOVERY|Digilent Analog Discovery 2]]
  
  
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 ===== 6. Problem Statement ===== ===== 6. Problem Statement =====
-The objective of this lab is to program the PIC32 processor to implement the functionality of a simple integer calculator that displays the result of X (?) Y where the operator, (?), will be add, subtract, multiply, or divide. The most recent computed result is continuously displayed on the 7-segment LEDs such that if an operation push button is held depressed and the X or Y switches change position, the new value is immediate seen on the LED display. +The objective of this lab is to program the PIC32 processor to implement the functionality of a simple integer calculator that displays the result of X • Y where the operator, •, will be add, subtract, multiply, or divide. The most recently computed result is continuously displayed on the 7-segment LEDs such that if an operation push button is held depressed and the X or Y switches change position, the new value is immediately seen on the LED display. 
  
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 The disparate assignments of processor IO pins connected to the eight slide switch inputs makes it imperative to use bit reading instructions. The instruction “s0 = PORTFbits.RF3;” is one way of sensing the state for slide switch SW0. To generate a 4-bit binary encoded for the value X as a 4-bit integer value, the following C programming instruction can be used: The disparate assignments of processor IO pins connected to the eight slide switch inputs makes it imperative to use bit reading instructions. The instruction “s0 = PORTFbits.RF3;” is one way of sensing the state for slide switch SW0. To generate a 4-bit binary encoded for the value X as a 4-bit integer value, the following C programming instruction can be used:
  
 +<code>
 X=PORTFbits.RF3+(PORTFbits.RF5≪1)+(PORTFbits.RF4≪2)+(PORTDbits.RD15≪3); X=PORTFbits.RF3+(PORTFbits.RF5≪1)+(PORTFbits.RF4≪2)+(PORTDbits.RD15≪3);
 +</code>
  
 Similarly, an expression can be created that will generate a value for another variable, Y, using SW4 through SW7. Similarly, an expression can be created that will generate a value for another variable, Y, using SW4 through SW7.
  
 ==== 7.3. Using the Push Button’s Inputs ==== ==== 7.3. Using the Push Button’s Inputs ====
-As with the slide switches, the push buttons must be individually set as PIC32 inputs. BTNR, BTNL, and BTNU are analog pins, and hence require disabling the analog input. Remember that PIC32 IO pins that also function as analog inputs must have the appropriate ANSELx bit set low. The state of the BTND push buttons can be read using the following C statement:+As with the slide switches, the push buttons must be individually set as PIC32 inputs. BTNR, BTNL, and BTNU are analog pins, and hence require disabling the analog input. Remember that PIC32 I/O pins that also function as analog inputs must have the appropriate ANSELx bit set low. The state of the BTND push buttons can be read using the following C statement:
  
 +<code>
 BTND=PORTAbits.RA15; BTND=PORTAbits.RA15;
 +</code>
  
-Figure A.1 shows that these five processor signals all have alternate uses. BTNR, BTND, and BTNC can be used as outputs for controlling servo motors and triggering the Analog Discovery 2. The 10K ohm resistors in series with the push buttons allow the buttons to be pressed with no effect on the PIC32 when these pins are configured as outputs. +Figure A.1 shows that these five processor signals all have alternate uses. BTNR, BTND, and BTNC can be used as outputs for controlling servo motors and triggering the Analog Discovery 2. The 10K ohm resistors in series with the push buttons allow the buttons to be pressed with no effect on the PIC32 when these pins are configured as outputs. 
-  +
-BTNL and BTNU are also used for MPLAB debugging and processor programming that renders them unavailable for push button inputs while the MPLAB X debugger is running. The PIC32 must be programmed for stand-alone operation to allow using BTNL and BTNU for inputs to the PIC32.+
  
 +BTNL and BTNU are also used for MPLAB debugging and processor programming that renders them unavailable for push button inputs while the MPLAB X debugger is running. The PIC32 must be programmed for standalone operation to allow using BTNL and BTNU for inputs to the PIC32.
  
-==== 7.4. Using a Seven Segment Display ==== 
-As previously discussed for the slide switch and push button inputs, the seven segment LED controls are scattered over multiple ports and pins. Again, Table E.1 of Unit 1 must be used to identify those pins that need to have the analog functionality disabled. Each segment should be set on or off using the LATxSET = BIT_xx and LATxCLR = BIT_xx instructions.  
  
-The particular [[http://www.luckylight.cn/UploadFiles/KW4-281XSB.pdf|multiple digit seven-segment LED display]] used in this application is a common anode device. The cathodes for the seven LED segment and the decimal point (DP) are active low, meaning the output pin must be set low to activate the LED segment. In addition, one of the four anodes (AN0 through AN3) must also be set low to allow the LEDs set by CA through CG to be turned on for the selected digit. For example, to display the number “5” on LED display number two, we would use the instructions shown in Listing 7.1. + 
 +==== 7.4. Using a 7-Segment Display ==== 
 +As previously discussed for the slide switch and push button inputs, the 7-segment LED controls are scattered over multiple ports and pins. Again, Table E.1 of Unit 1 must be used to identify those pins that need to have the analog functionality disabled. Each segment should be set on or off using the LATxSET = BIT_xx and LATxCLR = BIT_xx instructions.  
 + 
 +The particular [[http://www.luckylight.cn/UploadFiles/KW4-281XSB.pdf|multiple digit 7-segment LED display]] used in this application is a common anode device. The cathodes for the seven LED segment and the decimal point (DP) are active low, meaning the output pin must be set low to activate the LED segment. In addition, one of the four anodes (AN0 through AN3) must also be set low to allow the LEDs set by CA through CG to be turned on for the selected digit. For example, to display the number “5” on LED display number two, we would use the instructions shown in Listing 7.1.  
 + 
  
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 LATDCLR = BIT_7; // Segment F on LATDCLR = BIT_7; // Segment F on
 LATDCLR = BIT_13; // Segment G on LATDCLR = BIT_13; // Segment G on
-LATGSET = BIT_14; // Segment DP off+LATGSET = BIT_14; // Segment DP off
 LATBSET = BIT_12; // Display 0 off LATBSET = BIT_12; // Display 0 off
 LATBSET = BIT_13; // Display 1 off LATBSET = BIT_13; // Display 1 off
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 Variations of the code in Listing 7.1 must be used to light different numbers on each of the four digits. The last four instructions select the display digit. Variations of the code in Listing 7.1 must be used to light different numbers on each of the four digits. The last four instructions select the display digit.
  
-==== 7.5. Persistence: Lighting the Seven Segment Display ==== + 
-The display in Fig. 8.2 appears to have LED segments in three digits simultaneously displayed. As just discussed, the cathodes of all four of the seven segment LEDs are connected in parallel and the particular digit is selected by asserting the common anode pin high. In order to make the four-digit display appear that all four LED digits are simultaneously on, one should make sure each digit is displayed for a minimum of 1 millisecond. Listing 7.2 provides a simple software delay. Since this delay is dependent on the speed of execution, the “ms_cnt” will need to be changed depending on the speed of the core frequency. For the example shown in Listing 7.2, the ms_cnt value of 1000 is set to generate a one ms delay when the core frequency is set to 80 MHz.+==== 7.5. Persistence: Lighting the 7-Segment Display ==== 
 +The display in Fig. 8.2 appears to have LED segments in three digits simultaneously displayed. As just discussed, the cathodes of all four of the 7-segment LEDs are connected in parallel and the particular digit is selected by asserting the common anode pin high. In order to make the 4-digit display appear that all four LED digits are simultaneously on, one should make sure each digit is displayed for a minimum of 1 millisecond. Listing 7.2 provides a simple software delay. Since this delay is dependent on the speed of execution, the “ms_cnt” will need to be changed depending on the speed of the core frequency. For the example shown in Listing 7.2, the ms_cnt value of 10000 is set to generate a one ms delay when the core frequency is set to 80 MHz.
  
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 void sw_delay(int ms) void sw_delay(int ms)
 { {
-unsigned int ms_cnt; // 1 ms counter +unsigned int ms_cnt;        // 1 ms counter 
-    while(ms--) // ms loop counter+    while(ms--)     // ms loop counter
     {     {
-        ms_cnt = 10000; // Reset ms counter +        ms_cnt = 10000;     // Reset ms counter 
-        while(--ms_cnt); // wait for 1 ms+        while(--ms_cnt);    // wait for 1 ms
     }     }
 } }
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 ===== 8. Lab 1b ===== ===== 8. Lab 1b =====
 ==== 8.1. Development Plan ==== ==== 8.1. Development Plan ====
-Follow the system design plan presented in the Unit 1 description by completing the actions described in steps 1 through 5 of Table 8.1. After the planning activity has been completed, proceed to the design phase by setting up your development environment. Note that a test plan is included in the list of activities so that any test hardware and or software is included in the overall design.+Follow the system design plan presented in Unit 1 by completing the actions described in steps 1 through 5 of Table 8.1. After the planning activity has been completed, proceed to the design phase by setting up your development environment. Note that a test plan is included in the list of activities so that any test hardware and or software is included in the overall design.
  
 **Table 8.1. Software based system work flow.** **Table 8.1. Software based system work flow.**
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 ==== 8.2. Project Requirements ==== ==== 8.2. Project Requirements ====
-Using the five push buttons and eight slide switches onboard the Basys MX3, program the PIC32 processor to implement the functionality of a simple integer calculator that displays the result of X • Y where the operator, “•”, will be add, subtract, multiply, or divide. The button and switch operation assignments are given below. The most recently computed result is continuously displayed on the seven-segment LEDs such that if an operation push button is held depressed and the X or Y switches change position, the new value is immediately seen on the LED display. Only one push button is allowed to be pressed at a time. If multiple push buttons are simultaneously pressed, the result will not change.+Using the five push buttons and eight slide switches on-board the Basys MX3, program the PIC32 processor to implement the functionality of a simple integer calculator that displays the result of X • Y where the operator, •, will be add, subtract, multiply, or divide. The button and switch operation assignments are given below. The most recently computed result is continuously displayed on the 7-segment LEDs such that if an operation push button is held depressed and the X or Y switches change position, the new value is immediately seen on the LED display. Only one push button is allowed to be pressed at a time. If multiple push buttons are simultaneously pressed, the result will not change.
  
 **Table 8.2. Button operation.** **Table 8.2. Button operation.**
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 | BTNL (1)     | CLEAR RESULT: Result = 0  | | BTNL (1)     | CLEAR RESULT: Result = 0  |
  
-Note 1. BTNU and BTNL can only be implemented when MPLAB is not in debug mode.+Note 1: BTNU and BTNL can only be implemented when MPLAB is not in debug mode (see hardware.h in Unit 1, Appendix C).
  
-The eight slide switches shown in Fig. 8.1 are divided into two groups of four switches to generate values for X and Y by setting the switches in a binary fashion that are determined by equations 1 and 2.  +The eight slide switches shown in Fig. 8.1 are divided into two groups of four switches to generate values for X and Y by setting the switches in a binary fashion. The X and Y values are determined by equations 1 and 2.  
  
 $$X=(SW0 \cdot 2^0) + (SW1 \cdot 2^1)+(SW2 \cdot 2^2)+(SW3 \cdot 2^3)  Eq.1$$ $$X=(SW0 \cdot 2^0) + (SW1 \cdot 2^1)+(SW2 \cdot 2^2)+(SW3 \cdot 2^3)  Eq.1$$
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 Where SW0 through SW7 has a value of one if in the on (up) position, or zero if in the off (down) position.  Where SW0 through SW7 has a value of one if in the on (up) position, or zero if in the off (down) position. 
  
-{{ :learn:courses:microprocessor-io-lab-1b:figure-8-1.png?nolink |Figure 8.1. Partitioning of switches assigned to variables X and Y.}}+{{ :learn:courses:microprocessor-io-lab-1b:unit_1_-_photo_2.jpg?nolink&400 |Figure 8.1. Partitioning of switches assigned to variables X and Y.}}
 //Figure 8.1. Partitioning of switches assigned to variables X and Y.// //Figure 8.1. Partitioning of switches assigned to variables X and Y.//
  
 The mathematical operation on variables X and Y produce a new result that is displayed on the four digit seven-segment display, as shown in Fig. 8.2, whenever one of the push buttons is pressed. The operations associated with the push buttons are shown in the green text in Fig. 8.3. (Note: BTNL and BTNU are not functional when MPLAB X is running in debug mode.) The mathematical operation on variables X and Y produce a new result that is displayed on the four digit seven-segment display, as shown in Fig. 8.2, whenever one of the push buttons is pressed. The operations associated with the push buttons are shown in the green text in Fig. 8.3. (Note: BTNL and BTNU are not functional when MPLAB X is running in debug mode.)
  
-{{ :learn:courses:microprocessor-io-lab-1b:figure-8-2.png?nolink |Figure 8.2. Four digit- seven segment display.}} +{{ :learn:courses:microprocessor-io-lab-1b:unit_1_-_photo_3.jpg?nolink&400 |Figure 8.2. 4-digit 7-segment display.}} 
-//Figure 8.2. Four digit- seven segment display.//+//Figure 8.2. 4-digit 7-segment display.//
  
-{{ :learn:courses:microprocessor-io-lab-1b:figure-8-3.png?nolink |Figure 8.3. Operator assignments to push buttons.}}+{{ :learn:courses:microprocessor-io-lab-1b:unit_1_-_photo_4.1.jpg?nolink&400 |Figure 8.3. Operator assignments to push buttons.}}
 //Figure 8.3. Operator assignments to push buttons.// //Figure 8.3. Operator assignments to push buttons.//
  
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     - Consider the case when pin RF0 is programmed to be an input and the signal TRIG_1 is a digital output signal from an external device that is either 0 or 3.3V. What effect will pressing the BTNC button have on the processor RF0 pin when TRIG_1 is low and when it is high?     - Consider the case when pin RF0 is programmed to be an input and the signal TRIG_1 is a digital output signal from an external device that is either 0 or 3.3V. What effect will pressing the BTNC button have on the processor RF0 pin when TRIG_1 is low and when it is high?
     - Consider the case when pin RF0 is programmed to be an output and the signal TRIG_1 is a digital input signal to an external device. What effect will pressing the BTNC button have on the TRIG_1 signal when the RF0 output is low and when it is high?     - Consider the case when pin RF0 is programmed to be an output and the signal TRIG_1 is a digital input signal to an external device. What effect will pressing the BTNC button have on the TRIG_1 signal when the RF0 output is low and when it is high?
-  - Measure the loop execution time by toggling Pmod connector JA pin 1 at the start of the loop execution using the instruction LATCINC = 0x04. Connect a logic analyzer or oscilloscope probe to JA pin 1 and the ground or common connector to JA pin 5. The loop time is one half the period of the square wave generated at JA pin 1.  +  - Measure the loop execution time by toggling Pmod connector JA pin 1 at the start of the loop execution using the instruction LATCINV = 0x04. Connect a logic analyzer or oscilloscope probe to JA pin 1 and the ground or common connector to JA pin 5. The loop time is one half the period of the square wave generated at JA pin 1.  
     - What is this time?      - What is this time? 
     - Is this time expected?     - Is this time expected?
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 ====== Appendix A: Schematic Drawings ====== ====== Appendix A: Schematic Drawings ======
-{{ :learn:courses:microprocessor-io-lab-1b:figure-a-1.png?nolink |Figure A.1 Push button schematic diagram.}}+{{ :learn:courses:microprocessor-io-lab-1b:basys_mx3_schematic_buttons.png?nolink |Figure A.1 Push button schematic diagram.}}
 //Figure A.1 Push button schematic diagram.// //Figure A.1 Push button schematic diagram.//
  
-{{ :learn:courses:microprocessor-io-lab-1b:figure-a-2.png?nolink |Figure A.2 Schematic diagram of Basys MX3 slide switches.}}+{{ :learn:courses:microprocessor-io-lab-1b:basys_mx3_schematic_switches.png?nolink |Figure A.2 Schematic diagram of Basys MX3 slide switches.}}
 //Figure A.2 Schematic diagram of Basys MX3 slide switches.// //Figure A.2 Schematic diagram of Basys MX3 slide switches.//
  
-{{ :learn:courses:microprocessor-io-lab-1b:figure-a-3.png?nolink |Figure A.3 Four digit seven segment display schematic.}}+{{ :learn:courses:microprocessor-io-lab-1b:basys_mx3_schematic_ssd.png?nolink |Figure A.3 Four digit seven segment display schematic.}}
 //Figure A.3 Four digit seven segment display schematic.// //Figure A.3 Four digit seven segment display schematic.//
  
 +----
 +
 +[[{}/learn/courses/microprocessor-io-unit-1/start|Back to Unit 1]]
 +[[{}/learn/courses/unit-2/start|Go to Unit 2]]