Lab 2 – Intro to the SHARC EZ
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1. linking Otherwise you will get init1847 exe instead Buttons and Blinky Lights The three buttons on the SHARC EZ KIT Lite are connected to the following 2106x lines RESET e IRQI e FLAGI No doubt you are familiar with reset buttons The IRQ1 button can cause the 2106x to execute immediately a chosen subroutine The FLAG1 button when held will set a bit in the 2106x ASTAT register see the User s Manual The two buttons work in similar ways they both can send a signal to the 2106x However unless the program running on the processor in looking for the FLAGI signal it won t notice it The interrupt will always get the processor s attention although your program must enable the interrupt and you have to setup your interrupt service routine More on that later The blinky lights are connected to flags 0 1 2 and 3 These are controlled by bits in the ASTAT register Again consult your user s manual for details on the ASTAT register These lines of code with configure flags 0 2 and 3 as outputs flag 1 as input and will turn off the LEDs 2 and 3 bit set mode2 FLGOO FLG20 FLG30 configure flags as outputs bit clr mode2 FLG10 flagl as input bit clr astat FLG2 FLG3 clear the flags gt turn off LEDs It is left as an exercise for the students to figure out how to turn the LEDs on I suggest you become familiar with the blinky lights I can t really stress how useful they are for debugg2. s all you have to do r0 dm rx_buf 1 And do the similar thing to the output dm tx_buf 1 r0 A few more things to point out about audio interface The audio data is only 16 bits Incoming data is put in the 16 Most Significant Bits MSb of a data word Your program s outgoing data should also be put in the 16 MSb of the word The format of the data is fixed point two s complement fractional numbers When new audio data is ready the audio subsystem asserts the SPORTO receiving interrupt If you enable this interrupt you can set up an interrupt service routine which will read the data and store it in memory or something And actually this interrupt is already enabled for you in set up_1847 subroutine so you do not have to enable it again All you have to do is providing an interrupt service routine for this interrupt So how do we include this initl1847 asm in our program First of all assemble the file as usual Then link the resulting object file with our object file obtained from assembling your own asm file For example suppose your asm file is called lab2 asm The whole process is asm21k lab2 if no error this should give lab2 obj which will be used when linking asm21k init1847 This should give init1847 obj Now link them together 1d21k a ezlab2 lab2 init1847 If no error this should give the executable That s it Note that in order to yield lab2 exe the file Lab2 should come before init1847 when
3. Lab 2 Intro to the SHARC EZ KIT Lite Evaluation Board 64K ought to be enough for anybody W Gates III Overview So you ve written your program and simulated it and thoroughly debugged it Before you go burn 10 000 PROMs it might be a good idea to try your program on some real hardware Simulation is great but what if there s a bug in the simulator Impossible Well no matter how good your simulator is if you are in the real world your boss who long ago stopped being nice and started getting real wil not let you blame 10 000 recalled cell phones on a bug in the simulator That s where the Evaluation Board EVB comes in The EVB lets you run your actual program on the actual processor You get to test how our program handles interrupts how it interfaces with ports and peripherals The SHARC EZ KIT Lite EVB is pretty nice as testbed systems go It has a built in analog interface including an audio front end It has a 3 push buttons and 4 blinky lights one other light is the power LED And believe me as someone who has put in a couple of years debugging programs for this board and others like it you gotta have blinky lights SHARC EZ KIT Lite Features The SHARC EZ KIT Lite has of course an ADSP 2106x DSP operating at 4OMHz The processor itself has 2 blocks of internal memory of 512Kbits each The memory could be divided in to blocks and configured to be either 48 bits or 32 bits wide Alth
4. ect Com Port To download your program to the memory just go to File gt Open and then select the program to run The Host program will then download that program and show Downloading to board dialog When finished the Host program soft resets the board and your program will run If your program doesn t run try to adjust some settings on external hardware or maybe your code doesn t work Under the Settings menu you will find a bunch of reset commands which have different uses After you run program a while and you might want to restart your program you have to soft reset the board Your program will start over If you hard reset your program will be replaced by the default kernel in PROM and you have to download it to the board again The manual reset tells the Host program that you want to reset the board by yourself When you select this menu press the reset button on the board first then click OK on the dialog that appears The Host program also allows us to download any data directly to the memory or upload contents of the memory and dump to a file or view contents of the memory Just enter the range of the memory in hexadecimal format when asked Choose floating point if it s floating point data And click the button Everything is very straightforward Lab Assignment In this lab we will be using a function generator to provide an analog input signal We will display our analog outputs using an oscilloscope The progra
5. ependently of the others In your case you want to enable the SPORTO receiving interrupt You put some code like this bit set imask SPROI enable sportO rev irgs Fortunately this is already done for you in the init 1847 asm Still remember this file You do NOT have to enable this interrupt again Anyway you still need to put these lines of code somewhere in your program to enable the global interrupt preferably near the beginning bit set model IRPTEN enable global interrupts Programs Your first program is simple read data from ADC then copy that data out to DAC We do this at a sample rate of 48kHz So you just enable your interrupt and set up the interrupt service routine In your sprO service routine read from ADC into a register then copy that data to DAC Use a function generator and an O scope to verify your program Measure the time delay between the input and output signals Your second program will expand on the first Keep track of the last input When a new input arrives subtract the last input from it and output the difference Hint don t forget the format of the data read from the ADC is unsigned Try this with square triangle and sine wave inputs Sketch the results For the third program keep track of the last N inputs Output the average of the input and the last N inputs Allow N to be specified at assembly time Hint a circular buffer will be useful here Sketch the r
6. esults for inputs of square triangle and sine waves For the Report 1 What kind of filter did you implement in program 2 In program 3 2 What happens if your input signal has a frequency higher than 24kHz Using program 1 input a sine wave at 30kHz 40khz 48kHz and 60kHz Measure the frequency of the output signal for each of these inputs
7. ing or diagnostic purposes For example suppose you are debugging a program You want to make sure that a certain bit of code is being executed Simply turn on an LED right after that bit of code Another use is to toggle the LED s state inside a routine that is executed periodically If the routine is running the LED blinks Expansion Interface I won t go into this too much except to say that it is useful for connecting peripherals to the SHARC EZ KIT Lite board JTAG Connection You will discover that it is difficult to debug your programs when all you can do is blink some lights not that that s not useful But sometimes you want something that looks like the simulator In that case you use an Jn Circuit Emulator or ICE The ICE lets you do all the things the simulator does like single stepping setting breakpoints viewing memory and registers etc but with the real hardware with interrupts and analog interfaces and everything The disadvantage is that the ICE is expensive And delicate It s not something you let undergraduates play with much But if you re good Using the SHARC EZ KIT Lite In the last lab you learned how to use the assembler and linker to create an executable program from an assembly source file You also learned how to use the simulator to test and hopefully to debug your programs Now you are ready to use real hardware The first step is of course to create an executable The executable file c
8. mming techniques we will use are e Interrupt handling e Circular buffers As mention earlier the SPORTO will generate an interrupt for us when there is data ready to be retrieved So we will use this interrupt as a hint You must do the following things in your program 1 Provide an interrupt vector and an interrupt service routine ISR The vector is placed in the spr0_svc segment So put these lines of code in your program SEGMENT PM spr0_svc jump sprO_asserted ENDSEG Then in the pm_sram segment create a subroutine called spr0_asserted I suppose I should point out here that you don t have to call it sprO_asserted You can call it whatever you want as long as it matches the destination of the jump inthe sprO_svc segment Don t forget to end your service routine with the rt i instruction sprO_asserted do whatever finished reac Enable interrupts There are two steps to this First of all there is a global interrupt enable bit in the MODE1 register This bit has to be set before any interrupts can occur Then each interrupt source has its own mask bit in the IMASK register that has to be set before that source can cause interrupts Think of interrupts as lights in a house Then think of the global enable bit as the main breaker and the interrupt masks as the light switches The main breaker has to be closed before any of the lights can come on After that each light can be switched on or off ind
9. ontains a memory image of what your program i e it is a binary file whose contents would go straight into the memory of the DSP As you know the simulator uses the executable However there is really no way to put the contents of this file directly into the memory of the DSP Here is where the SHARC EZ KIT Lite Host program comes in You can find this program under the SHARC EZ KIT Lite program group under the Start menu The program allows you to download your executable to the DSP s memory and execute it The SHARC EZ KIT Lite EVB just like other microprocessor based circuits starts with the power on routine that stores in the PROM The routine initializes the UART chip which controls the serial port and waits for the Host program to communicate with it While waiting it plays the Peter Gunn s theme through the output audio port If you have speakers you can here the song The Host program allows you to download your executable to the memory and replace whatever that already in the memory at startup then soft reset the board so your program can run When you first open the Host program the program will try to locate and communicate with the EVB board If everything went okay it will show Communications with board are OK Otherwise it will complain something and we have to fix the error The error may be because the wrong Com port on the PC is being used You can change this in the program under the menu Settings gt Sel
10. ough the ADSP 2106x allows the use of external memory this board does not have the external memory to worry about Here is a list of the SHARC EZ KIT Lite s main selling points e Analog interface 16 bit stereo audio interface e 3 user input push button switches and 4 output LEDs e Expansion interface Eurocard DIN 96 e JTAG connection for In Circuit Emulator ICE e RS 232 host connection Let s examine each in closer detail Analog Interface For audio applications this board is the thing All the analog interfacing has been done for you through the AD1847 Stereo Codec The audio interface has 2 1 8 jacks one for input A D and one for output D A The sample rate for audio signals can be set by software to any of a fixed set of 16 rates from 8kHz to 48 kHz So you can t have any rate you want you have to pick one that Analog Devices offers you The ADSP 2106x DSP connects to the codec through a serial port on the chip called SPORTO This means some initial setup has to be done in order to make the codec work Luckily this is already done for you The file init1847 asm provides the basic setup for AD1847 codec to use with SHARC EZ KIT Lite Let s look at some code from the file GLOBAL setup_1847 GLOBAL sptO_asserted GLOBAL rx_buf tx_buf A GLOBAL directive in front of a label tells that the label is expected to be used by other assembly program and the definition of the label could be found somewhere in
11. this file So the other files namely your own asm files do not have to define these symbols themselves Instead EXTERN directive is used to tell the linker to look for these symbols somewhere else So you have to put EXTERN setup_1847 EXTERN spt0O_asserted EXTERN rx_buf tx_buf in your program if you expect to use the initialization of the codec from this init1847 asm Well what do these symbols mean then setup_1847 is a subroutine you have to call in order to setup the codec So you put the code like this call setup_1847 somewhere in the very beginning of your main program We will talk about subroutines more in Lab 3 spt0_asserted is the subroutine that is called each time the processor transmits data to the codec That is the SPORTO transmitting interrupt is asserted A useful set of code is already put in the asm file so there is nothing you have to do about this symbol Now the very important variables rx_buf and tx_buf rx_buf stores the information received by the codec That is we are talking about the input signal And whatever our output is we put in tx_buf The two variables are 3 words long The following table describes each word for each variable rx_buf tx_buf word 0 Status data Configuration data word 1 Left channel A D Left channel D A data data word 2 Right channel A D Right channel D A data data Suppose you wanted to read some incoming audio data from the left channel Here
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