Introduction to Lab. 3

Transcription

1 Solving a Lab 1 Issue Introduction to Lab. 3 Also includes Solving a Lab. 1 issues Using the graphics LCD with your assignment 1 Rediscuss the Watchdog timer for Assignment 2 Many people have said My Enable / Disable PF input does not work How can the code not work? They (without doing AND and OR) are 1 line long void Enable(void) { *pfio_inen = 0x0F00;} void Disable(void) { *pfio_inen = 0x0000;} 2/25 Item 1 -- Higher priority read than writes on Blackfin Processor Architecture Blackfin Architecture is designed for DSP algorithms Write operations occur 1000 times less often than read operations in many DSP programs So the architecture handles read operations from memory at a higher priority than write void Enable(void) { *pfio_inen = 0x0F00; ssync( ); } // Force write 3/25 Item 2 Need to have a new mental model of what Disable Input does Enable PF_INEN Read FIO_FLAG_D expect to read 4 Disable PF_INEN Read FIO_FLAG_D Read 4 therefore Disable did not work 4/25

2 Problem Misunderstanding of what *pfio_inen does Assignment 2 will use watchdog timer and PF interrupts at the C++ level *pfio_inen = 0, disconnects the device input from the FIO_FLAG_D register It does not change the existing value in the FIO_FLAG_D register so correct test is Enable PF_INEN Read FIO_FLAG_D expect to read 4 Disable PF_INEN Set switches to 6 Read FIO_FLAG_D Read the old value of 4 therefore Disable did work 5/25 General format for writing an interrupt service routine in CCES is volatile int debuginfo_numberinterrupts = 0; #pragma interrupt void ThisIsISR_Not_Subroutine(void) { // Acknowledge Interrupts for this device // Do ISR task debuginfo_numberinterrupts ++; } 6/25 Friday s lecture gave details of code you can use in Assignment 3 Stop and Start WatchDog Interrupts Cause a software interrupt -- SWI for testing your ISR Tell the Event Vector Table (EVT) where your ISR has been placed in your cod

3 Initialize WDOG interrupts and cause SWI (SoftWareInterrupt) to occur in C++ The neat stuff writing an ISR using C++ NOTE use of PRAGMAs C++ extensions `Very interesting bug The correct code avoiding the hardware race This code works if WATCHDOG_COUNT is 0xFFFF (16 bit value) But not when WATCHDOG_COUNT is 0x10000 a (32 bit value) This probably associated with a hardware `race`condition

4 MUCH faster ISR and also NMI (looks like possible midterm material to me) Using the LCD graphics screen to display your Assignment 1 output 1. Download two new libraries to your Workspace directory NewLibraries CoffeepotLibraryUsing SPI.dlb LCDgraphicsLibrary.dlb 2. In Assignment 1 -- Settings Linker remove the link to the CoffeepotLIbraryNotUsingSPI.dlb Add links to the new libraries 3. Change your Assignment 1 main to USE_TEXT_GUI USE_SPI_GUI Rebuild your code 4. Hook up the LCD graphics screen according to the very first ENCM511 lab 5. Run Assignment 1 again 14 /25 Lab 3 Part 1 Timing SW3 switch movements Use uttcos to set up a task that will allow you to read switch SW3 to change the speed at which LEDs flash Long SW3 switch presses slow the LED flash down, short switch presses speed LED flash up SW1 switch up causes the length of time SW3 was held pressed (in ¼ seconds) to be displayed Sw1 down normal LED flash operation Lab 3 Part 2 Find the the Analog Devices TMP03 (thermal sensor) in your lab kit. Find the TMP03 reference data sheet on the web. Read how to use to calculate temperature Hook up to Vcc and Ground and then examine TMP03 output on the scope. Expect to see a 30 Hz pulse width modulated signal Do not expect to see changes in this PWM power shape with your finger temperature You will need more accuracy than that 15 /25 16 /25

5 Part 3 Timing SW4 switch movements Make a version of your SW3 code from Lab 3 part 1 to work when you change the position of SW4 Make SW1 and SW2 control the display of SW4 movement on LEDs SW1 low SW2 low flash control SW1 high SW2 low show time SW4 low SW1 high SW2 high show time SW4 high This will probably work well with SW4 uttcos tasks activated every 1 / 10 sec 17 /25 Part 4: Measure temperature using TMP03 Hook up TMP03 to SW4 and now make the switches have the following functions SW1 low SW2 low flash control SW1 high SW2 low show time SW4 low SW1 high SW2 high show time SW4 high SW1 low SW2 high display temperature Try this with SW4 uttcos tasks activated every 1 / 10 sec and as fast as possible (every tick) 18 /25 Part 5 More accurate temperature measurement You will find that uttcos can t respond fast enough to get accurate temperature measurements We will have to launch a uttcos hardware task that activates the Blackfin Timer 2 in capture mode (to capture hi and low times) Use uttcos to poll the Blackfin Timer 2 ready flag to see when the timer has captured the signals Use the Blackfin Timer 2 information to calculate temperature and control the LED flash rate We now have developed a bio-feedback device 19 /25 So now we need to switch to a chalk board discussion of Waiting for switch signals or timer signals Will completely kill any operating system Polling for switch signals or timer signals The approach needed for a co-operative scheduler Interrupts from switch signals or timer signals When sensible in a co-operative scheduler (not often) 20 /25 When sensible in a pre-emptive scheduler.