FORTHdsPIC User Manual
Contents
1. LOOP SPACE Frequency CR FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 212. FORTHdsPIC User Manual Contents FORTHAdSPIC User Manuals eege eg 1 La TOUT OM eens ccteeiepeticusrus sou cetunscuseensinasalvcndestisaecaetiisetaceslsncendeluasdmeuvsedontucubenwiaduetadentiemiyetceetieeded 2 2 SYSTEM e Uu e 2 2 1 MicroStick Il Development Board iccciiecsetsicncesisnccieede cadeucsventunsadennnecunentQeaiGanisonsdaacertadennveceinaseeats 2 2 2 Custom Development Board EE 2 So Installing FORTHASPIC ee 3 3 1 MicroStick Il Development Boar wczcics ccs ccsssccesassiaces veascanzsaas EENEG ENEE SEENEN 3 3 2 Custom Development Board si caress ccennceeansienseandeaudinddeunecesueereansdeacivndverubindlavac danusreuntiaserenddaau 3 4 R nning FORTHASPIC TE 4 4 1 MicroStick Il Development BO ai arcu ccsdiscvcsceasaeatecsasetoreseyuctecunveidiesasiethevacienelacaedeumvardeenicntsn 4 4 2 Custom Development Board EE 4 5 Running FORTH in Interpreter JEE geseedgenbtrege et eege eegene egen 5 5 1 SOT 5 6 Running g lteg eru EE 6 6 1 Creating New Words with the Compiler EE 6 O 2 FORTH deele TTT 7 6 3 How Forth programs are stored amp run in FORTHASPIC sssssssssssssssssssssssrsssssrrsserresreeennsssreenssene 8 7 Moving the Forth code to non volatile Flash memon 10 7 1 Compiling code for the Flash memory EN 11 7 2 Running an Embedded Application ceciccsiscccaccescseecasenseecssencessaseeveansacauoeesdarsweccdaenvedeonenverteseunen 12 Appendix 1 FORTHdsPIC Basic Instruction Set out esesgdeteegegen REENEN een 13 Ap
3. definitions are compiled and code saved in the code area of RAM Any other words are executed immediately FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 6 6 1 3 Running the compiled program The vocabulary entry and the run time code for the new word definition CALC is stored in RAM memory and will be lost if the power to the board is switched off or the processor RST Reset button pressed To run CALC with the same numbers as before type 3 4 6 CALC at the command prompt 10 gt 3 4 6 CALC 8 OK 10 gt The Interpreter reads the command line from left to right and pushes the three numbers onto the Last In First Out Parameter Stack in order When CALC is executed the top two 4 and 6 are popped off the stack multiplied together and the result pushed on the stack The top two parameters now 24 and 3 are SWAPped popped off the division performed and the result 8 pushed back on the stack Finally the print number command pops the result and displays it Note 1 Now that CALC is a defined word it can be used to operate on any three numbers 2 CALC can be used inside new definitions alongside the standard words 6 2 FORTH Programming It is possible to create one very large colon definition using just the standard words of the FORTHdsPIC instruction set From the debugging point of view and of someone else trying to understand your work this is very definitely the worst way to program in Forth
4. BENCH HEADINGR BM1 BM2 BM3 BM4 BM5 BM6 BM7 BM8 BM9 BM10 BM11 Full Test BM12 BM13 BM14 BM15 BM16 FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 19 Fast Fourier Transform program Program 8 Fast Fourier Transform 256 point 16 bit signed complex W G Marshall 2014 257 ARRAY1D REAL 257 ARRAY1D IMAG 256 ARRAY1D C S 257 ARRAY1D POWER VARIABLE J1 VARIABLE K1 VARIABLE L1 VARIABLE M1 VARIABLE M2 VARIABLE M3 VARIABLE U1 VARIABLE U2 VARIABLE SFACT REORDER 1J1 Decimation in time 256 1 DO IJ1 lt IF J1 REAL DUP I REAL DUP ROT ROT SWAP THEN 128 K1 BEGIN K1 DUP J1 lt WHILE J1 OVER J1 2 K1 REPEAT J1 LOOP SCALE 0 257 1 DO Automatic scaling REAL DUP 13312 gt IF DROP NOT LEAVE ELSE 13312 lt IF DROP NOT LEAVE THEN THEN IMAG DUP 13312 gt IF DROP NOT LEAVE ELSE 13312 lt IF DROP NOT LEAVE THEN THEN LOOP IF 257 1 DO I REAL DUP 2 SWAP IMAG DUP 2 SWAP LOOP SFACT DUP 2 SWAP C THEN FFT 1 DUP M1 SFACT 256 M2 91DO 256 point FFT SCALE M2 DUP 2 SWAP C 0 M3 M1 DUP 2 M1 DUP K1 C 1 1DO M3 DUP C S U2 192 255 AND C S U1 2561DO 1K1 L1 L1 REAL DUP U1 32767 L1 IMAG DUP U2 32767 ROT SWAP SWAP U1 32767 ROT U2 32767 DUP I IMAG SWAP L1 IMAG I IMAG DUP I REAL SWAP L1 REAL I REAL M1 LOOP M3 M2 M3C LOOP LOOP FORTHdsPIC User Manual Vsn 1 0 W
5. Microstick If you use this method the RAM is cleared and typing MAIN to re run the program will result in an Undefined error message The user program will now only run from Reset or Power on auto boot This is the stand alone or embedded mode Here is a code example that shows how different programs can be loaded and run in RAM and Flash It also shows that commands can be run by the interpreter in between colon definitions Program 3 RAM versus Flash memory Benchmark Test SETFLSH FHEADING CR Flash Benchmark CR MAIN FHEADING TIMSET TIMSRT 10001 1 DO SP LOOP TIMSTP TIMRD 40 M MOD BM1 8 F usecs DROP FLASH SETRAM RHEADING CR RAM Benchmark CR BENCH RHEADING TIMSET TIMSRT 10001 1 DO SP LOOP TIMSTP TIMRD 40 M MOD BM1 8 F usecs DROP FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 11 SETFLSH sets the Flash memory flag and the next two colon definitions FHEADING and MAIN are compiled into RAM accordingly FLASH copies the code into Flash memory SETRAM clears the Flash flag so subsequent compilation will yield code that will execute in RAM The vocabulary and code entries of RHEADING and BENCH are appended to those of the other two in RAM Type BENCH at the prompt and the benchmark program for RAM based programs produces RAM Benchmark BM1 7501 usecs OK 10 gt Type MAIN at the prompt and the benchmark program for Flash based programs produces Flash Benchma
6. The drawback of using a push down stack for storing intermediate results is keeping track ensuring that each Forth word begins execution with its operands on top of the stack in the correct order Following a piece of source code involves keeping an image of the stack in your mind at every stage This becomes difficult with more than three stacked items so annotating a source listing with stack snapshots is essential The table below shows the data on the stack during execution of the CALC example TOS Top of Stack Parameter Stack Before After After SWAP After TOS 6 24 3 8 TOS 1 4 3 24 TOS 2 3 Fig 4 State of Parameter Stack as CALC executes FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 7 6 3 How Forth programs are stored amp run in FORTHdsPIC 6 3 1 Format amp Storage A compiled Forth program consists of a list of 16 bit address links each pointing to the code for that word That code could be the start of another list of addresses or actual executable machine code There is a problem though The dsPIC has what is called a modified Harvard architecture where data and program memories are separated This means that executable code is stored in Program memory but Forth address links are treated as data and stored in Data memory Early versions of Forth ran on microprocessors with a single memory space for both Data and Program Fortunately there is a way of foolin
7. to the correct serial COM port with settings 19200baud 8bits No Parity and Transmit Delay 200ms Save the FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 4 template so it s selected whenever the MicroStick is plugged in 4 The board is powered from the USB link so with the slide switch set to A press the RST button and a title message with FORTH prompt should appear in the emulator window FORTHdsPIC Ven X X C W G Marshall 10 gt 5 Running FORTH in Interpreter Mode From now on operation of FORTHdsPIC is largely independent of the hardware platform Fig 3 below shows a minimal system for program development based on the MicroStick II fitted with a dsPIC33 device Fig 3 FORTHdsPIC running on a MicroStick Communication is via the TeraTerm window MPLAB IDE is open in the background 5 1 Simple Command Line Basic calculations can be performed immediately by typing Forth commands and numbers separated by spaces after the command prompt followed by Return Max length 80 characters 5 1 1 Command Prompt The Command prompt gt is preceded by a number indicating the number base in use The default is decimal 10 and its value is held in the system variable BASE Typing HEX at the prompt will change the base to hexadecimal 16 DECIMAL will change it back FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 5 5 1 2 Command Line Interpreter At the command prompt gt type 6 4 3
8. when two new user word definitions CALC and PRINT are incorporated in the definition of a third MAIN Program 2 Print results of simple calculation CALC SWAP Perform calculation with top 3 stack items PRINT CR Print TOS item followed by NewLine MAIN CALC PRINT Combine CALC and PRINT into a new word MAIN FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 9 Fig 6 below illustrates the program flow of the new word MAIN As before the command interpreter searches for MAIN in the vocabulary and begins execution when it finds the entry and its code pointer value of 2812 This time however the pointer links through to a new definition CALC which also resides in RAM Hence the absence of the PSV bit on the link address of 2800 Note again that the vocabulary entries for CALC and PRINT are not required for MAIN to run Vocabulary Forth Code Address Code Address Code Function 2000 4 2800 0000 CALC C 8CBC SZ A 8C3A SWAP L 8CD8 C 87FE TRET 00 280A 0000 PRINT 28 8A52 2007 05 8900 CR P 87FE TRET R 2812 0000 MAIN 2800 CALC N 280A PRINT T 87FE TRET gt End DA 28 200F 4 M A N 12 28 Fig 6 Vocabulary entry and Forth linked code for example MAIN program 7 Moving the Forth code to non volatile Flash me
9. After the divide the linked Forth code CALC ends with TRET which pops the last PC off the Return stack before jumping to NEXT As this is the end of the program control returns to the Interpreter and the command prompt The important point to notice is the difference between executing CALC as a command line and executing the compiled version When you type in a series of commands and data at the prompt Section 5 1 2 the Interpreter searches for each one in the Interpreter vocabulary locates its code and executes it until the end of the line is reached When CALC is compiled Section 6 1 1 and then run at the command prompt the Interpreter pushes the three parameters on the stack before searching all the vocabularies for the CALC entry Once the CALC word begins executing the vocabularies are no longer referenced because the compiled code now contains all the pointers in a list Hence compiled code will always run much faster than interpreted code Note that the Pointer to Code in the User Vocabulary Fig 5 does not have Bit 15 set because the newly compiled code is in RAM This will change if user code is moved to Flash memory See Section 7 Take a look at the listing for FORTHdsPIC itself all the speed sensitive word definitions are in machine code while those printing to the terminal say are composed of Forth linked lists 6 3 4 How FORTHdspPIC runs more complex compiled code This example serves to show the code generated Fig 6
10. EXECUTE address located at ERASE RECKEN pointer QUIT Exit program amp clear SETFLSH Set Flash status flag all stacks CREATE Create new definition with lt name gt and SETRAM ne BEE DOES gt action code 8 Loop Structures Word Stack Before Stack After Action n1 Execute words between DO and LOOP n2 n1 times n1 is the loop index n2 n1 DO LEAVE LOOP n2 incremented by 1 each time round the loop Accessed within the loop by using which leaves the index on TOS Optional LEAVE forces early exit n1 n2 n1 DO LEAVE n3 LOOP n2 As for DO LOOP but index increment set by n3 BEGIN WHILE REPEAT Execute a loop WHILE TOS True BEGIN UNTIL Execute a loop UNTIL TOS True BEGIN AGAIN Execute a continuous loop FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 16 Conditional Structures Word Stack Before Stack After Action Flag If flag True words following IF executed and words after ELSE skipped IF ELSE THEN If flag False words between IF and ELSE skipped and words after ELSE executed n CASE begins list of conditional actions If n number before OF then CASE OF ENDOF ENDCASE words between OF and ENDOF executed and execution skips to ENDCASE If not equal skip to next OF ENDOF line Embedded Functions Word Sta
11. G Marshall 2014 Page 20 POW 2571DO Calculate frequency power data REAL DUP 16384 I IMAG DUP 16384 POWER LOOP FMAX 0 U1 Calculate maximum power 257 1 DO POWER U1 MAX U1 LOOP PULSE 17 1 DO Create pulse data for TEST DUP I REAL 0 I IMAG LOOP DROP 257 17 DO OI REAL O1IMAG LOOP S1 0 804 1608 2410 3212 4011 4808 5602 6393 7179 7962 8739 9512 10278 11039 11793 Create Sine table 12539 13279 14010 14732 15446 16151 16846 17530 18204 18867 19519 20159 20787 21403 22005 22594 23170 23731 24279 24811 25329 25832 26319 26790 27245 27683 28105 28510 28898 29268 29621 29956 30273 30571 30852 31113 31356 31580 31785 31971 32137 32285 32412 32521 32609 32678 32728 32757 32767 127 192 DO I C S 1 LOOP S2 1 256 193 DO DUP 192 SWAP C S I C S 1 LOOP DROP 3 256 128 DO I C S NEGATE I 128 C S LOOP SIN S1 2 S3 Create Sine Cosine table VIEW 128 1 DO Print Real frequency data in a table 18 1 DO I REAL 7R LOOP CR 8 LOOP TEST Perform FFT on a single rectangular pulse SIN 16000 PULSE TIMSET TIMSRT REORDER FFT TIMSTP Time reorder and FFT VIEW 20 SPACES Scaling Factor SFACT TIMRD 40 M MOD CR 24 SPACES D usecs DROP GRAPH POW FMAX U1 22 U1 Print power graph CR Power CR 022 DO 6 SPACES A1 1 DO I POWER U1 J lt IF SPACE ELSE HH THEN LOOP CR 1 LOOP 6 SPACES 42 1 DO
12. SRT 10001 1 DO 111 DO C LOOP SP LOOP TIMSTP Read constant CR TIMRD 40 M MOD BM7 8 F usecs DROP BM8 TIMSET TIMSRT 10001 1 DO 11 1 DO 9 DUP LOOP SP LOOP TIMSTP DUP ToS CR TIMRD 40 M MOD BM8 8 F usecs DROP BM9 TIMSET TIMSRT 10001 1 DO 11 1 DO 9 1 LOOP SP LOOP TIMSTP Increment ToS CR TIMRD 40 M MOD BM9 8 F usecs DROP BM10 TIMSET TIMSRT 10001 1 DO 11 1 DO 9 9 gt LOOP SP LOOP TIMSTP Greater than CR TIMRD 40 M MOD BM10 8 F usecs DROP BM11 TIMSET TIMSRT 10001 1 DO 11 1 DO 9 9 lt LOOP SP LOOP TIMSTP Less than CR TIMRD 40 M MOD BM11 8 F usecs DROP BM12 TIMSET TIMSRT 10001 1 DO 1 BEGIN 1 DUP 11 lt WHILE REPEAT BEGIN WHILE SP LOOP TIMSTP CR TIMRD 40 M MOD BM12 8 F usecs DROP BM13 TIMSET TIMSRT 10001 1 DO 20 BEGIN 1 DUP 11 lt UNTIL BEGIN UNTIL SP LOOP TIMSTP CR TIMRD 40 M MOD BM13 8 F usecs DROP TEN NINE TEN EIGHT NINE SEVEN EIGHT SIX SEVEN FIVE SIX FOUR FIVE THREE FOUR TWO THREE ONE TWO BM14 TIMSET TIMSRT 10001 1 DO ONE SP LOOP TIMSTP Compile CR TIMRD 40 M MOD BM14 8 F usecs DROP BM15 TIMSET TIMSRT 10001 1 DO 9 2 3 4 5 SP LOOP TIMSTP SP Maths CR TIMRD 40 M MOD BM15 8 F usecs DROP BM16 TIMSET TIMSRT 10001 1 DO 900 900 M 9 M 90000 DP Maths DNEGATE D SP LOOP TIMSTP CR TIMRD 40 M MOD BM16 8 F usecs DROP
13. TOS AND ne and TOS 1 NOT 1 s Compliment ni i Logical Inclusive OR of pattern geeiert OR n2 E TOGGLE RAM address data byte pattern at TOS and TOS 1 RAM address nt d Logical Exclusive OR XOR nz of TOS and TOS 1 Comparison Flag state 0 False 1 True Word Stack Before Stack After Action Word Stack Before Stack After Action n1 flag i n flag TOS True if n2 n1 R n2 ES 0 gt TOS True ifn gt 0 ni flag TOS True if n2 gt n1 flag gt n2 Falei n seni 0 lt TOS True ifn lt 0 1 fl 1 A aE TOS True if n2 lt n1 MAX 3 i Larger of TOS and False if n2 gt n1 TOS 1 left on TOS 1 fl i 1 U lt 25 Gen a e MIN r Smaller of TOS and deg n TOS 1 left on TOS False if n2 gt n1 n flag 0 TOS True if n 0 Terminal I O Word Stack Before Stack After Action Word Stack Before Stack After Action n Print signed SP Character 0 TOS keyboard S number n with INKEY character or 0 if trailing space none available n Print unsigned SP character S U sumberin with KEY Wait for keyboard SE Input trailing space nh Print signed DP Read line of D nl number with trailing QUERY keyboard input to space buffer n Print formatted character S F nh signed DP number in EMIT Print ASCII e character nl field width n n Print formatted Print Carriage R n1 signed SP number n1 CR Return and Line in field width n Feed RAM address Print SP number Print Space stored at RAM SPACE EEN address Pointer character Get string character n COUNT P
14. al Vsn 1 0 W G Marshall 2014 Page 13 Memory Word Stack Before Stack After Action Word Stack Before Stack After Action n Copy n bytes from RAM address Write 16 bit CMOVE RAM address S RAM start address S l n number n to RAM RAM address D to destination D address n1 Fill n1 bytes with RAM address Write byte n to FILL n2 character n2 starting C n RAM ddei RAM address at RAM address RAM address n Read 16 bit number n n Creates 1D array at RAM address to ARRAY1D lt name gt size n TOS words RAM address n n Moves Code Ce EE Se pointer in RAM up by n bytes Arithmetic SP Single Precision 16 bit DP Double Precision 32 bit Word Stack Before Stack After Action Word Stack Before Stack After Action n1 r SP to SP signed n r SP to SP signed n2 addition 2 multiply by 2 nl n23r nx23r n1 r SP to SP signed n r SP to SP signed n2 subtract 2 divide by 2 n2 n1 gt r n 2 gt r n1 r SP to SP signed n r SP to SP signed 3 n2 multiply 1 increment nixn2 gt r n 139r n1 r SP to SP signed n r SP to SP signed n2 division 1 decrement n2 n1 gt r n 13r n1 rh SP to DP signed n r SP to SP signed M n2 rl multiply 2 increment by 2 ni x n2 gt rh rl n 29r n1 rh SP to DP
15. ck Before Stack After Action n WAIT Wait for n milliseconds TIMSET TIMSRT TIMSTP a TIMSET sets up 32 bit user timer TIMSRT starts timer TIMSTP stops TIMRD timer TIMRD reads timer and pushes on stack Timer clocked at 40MHz Servo No SVOSET initialises OC1 to OC4 as PWM outputs SERVO moves Servo No SVOSET SERVO Angle 1 4 to Angle 0 180 degrees FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 17 Appendix 2 Sample Forth programs Walking robot program with four servomotors The DO LOOPs rotate each servo by one degree followed by a 10ms delay each time round the loop This slows the joint movement down to a realistic level Program 6 Servo test for walking robot STEP performs one leg movement cycle Servo 1 right ankle Servo 2 left ankle Servo 3 right hip Servo 4 left hip HOME Starting position Left foot forward right back 90 1 SERVO 90 2 SERVO 120 3 SERVO 120 4 SERVO LEANLEFT Balance on left leg 121 90 DO I 2 SERVO 10 WAIT LOOP 141 90 DO I 1 SERVO 10 WAIT LOOP 129 140 DO I 1 SERVO 10 WAIT 1 LOOP ROTATELEFT Rotate on left leg 59 120 DO I 3 SERVO I 4 SERVO 10 WAIT 1 LOOP LEANLEFTBACK Return right leg to floor 89 120 DO I 2 SERVO 10 WAIT 1 LOOP 89 130 DO I 1 SERVO 10 WAIT 1 LOOP LEANRIGHT Balance on right leg 59 90 DO 1 SERVO 10 WAIT 1 LOOP 39 90 DO I 2 SERVO 10 WAIT 1 LOOP 51 40 DO I 2 SERVO 10 WAIT LOOP ROTATERIGHT Ro
16. d User vocabulary 10 gt VLIST DUP DUP DROP SWAP OVER ROT PICK 2DROP 2DUP 2SWAP gt R R gt R CMOVE FILL C C ARRAY1D D M U M MOD U MOD M MOD MOD 2 2 1 1 2 2 NEGATE DNEGATE ABS DABS S gt D AND OR XOR NOT TOGGLE gt lt U lt 0 0 gt 0 lt MAX MIN U D F R COUNT TYPE INKEY KEY QUERY EMIT CR SPACE SPACES DECIMAL HEX BASE J K DPL CODE HERE SP DEPTH VLIST FORGET C CONSTANT VARIABLE EXECUTE CREATE ALLOT DOES gt QUIT ABORT ERASE FLASH SETFLSH SETRAM TIMSET TIMSRT TIMSTP TIMRD WAIT SVOSET SERVO UI IF THEN ELSE BEGIN WHILE REPEAT UNTIL AGAIN DO LOOP LOOP LEAVE CASE OF ENDOF ENDCASE Stack Manipulation Word Stack Before Stack After Action Word Stack Before Stack After Action n n nh n Duplicate TOS nl Drop Double DUP p 2DROP So Precision number n n z DUP BEES Duplicate TOS if TOS nh nh not equal to zero 7 2DUP nl nl Duplicate Double n nh Precision number DROP Drop TOS nl nih n2h n1 n2 nil n2l Exchange Double SWAP n2 n1 ao TOSand 2SWAP n2h nih Precision numbers n2i nil ni ne n Move TOS to OVER n2 ni Copy TOS 1 to TOS gt R Raak n2 ni n3 n Move Top of Return ROT n2 n1 Rotate TOS 2 to TOS R gt P stack to TOS n3 n2 n be Copy TOS n to TOS n Copy Top of Return PICK 5 n n 2 shown R stack to TOS FORTHdsPIC User Manu
17. g the dsPIC chip into believing that an area of Program Flash memory is actually Data RAM Those familiar with PIC chips will be aware of the TBLRD and TBLWT instructions which allow data to be read from and written to program memory The PIC24 dsPIC devices also have an operating mode called Program Space Visibility PSV 6 3 2 Program Space Visibility In FORTHdsPIC a 32Kbyte section of program Flash space is mapped into data memory RAM beginning at address 8000h This is why the compiled Forth links all have Bit 15 1 The PSV system is enabled from startup so every time the processor reads data from an address with Bit 15 set it gets it from Flash memory not RAM Here are the Vocabulary and Code entries for the compiled CALC example User Forth Code in RAM Address Code 2800 0000 Forth code header 2802 8CBC 2804 8C3A SWAP 2806 8CD8 2808 87FE TRET threaded return User Vocabulary Entry in RAM Address Code 2000 4 Name string length 2001 C 2002 A 2003 L Name string 2004 C 2005 00 Pointer to Code L 2006 28 Pointer to Code H Fig 5 Vocabulary entry and Forth linked code for example CALC program 6 3 3 How FORTHdsPIC runs the CALC example compiled code Two pieces of code are produced by the Compiler for each colon definition Fig 5 When CALC is subsequently typed at the command prompt the Interpreter scans the vocabular
18. h for and loading of a driver 3 Run the terminal emulator in my case use TeraTerm and make sure it links to the correct serial COM port with settings 19200baud 8bits No Parity and Transmit Delay 200ms Save the template so it s selected whenever the MicroStick is plugged in 4 The board is powered from the USB link so with the slide switch set to A press the RST button and a title message with FORTH prompt should appear in the emulator window FORTHdsPIC Ven X X C W G Marshall 10 gt 4 2 Custom Development Board Once programmed with the FORTHdsPIC firmware MPLAB is no longer needed but the board will still need to be powered Power supply and connection to the PC terminal emulator will depend on the particular board design In order to edit compile and run FORTH code you will need a host PC running a terminal emulator and a USB or UART USB bridge cable 1 Either connect the bridge cable to Tx Rx and Gnd pins of a UART1 header on the board These are the pin numbers for a 28 pin DIP package dsPIC33 These pins will be assigned to UART1 by FORTHdsPIC when it boots up Gnd Pin 19 Black Rx Pin 21 Orange Tx Pin 22 Yellow or connect a USB cable to the target board if it has a UART USB bridge chip fitted 2 Plug the other end of the cable into the PC Again there may be a one time search for and loading of a driver for the bridge chip 3 Run the terminal emulator in my case use TeraTerm and make sure it links
19. mory Once the Forth code has been debugged while stored in RAM it can be moved to the dsPIC s Flash memory so that it won t disappear when the device power is removed It will also auto boot from power up or Reset FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 10 7 1 Compiling code for the Flash memory The only difference between code generated to run in RAM and that for Flash memory is in the memory address references for the compiled code which will usually need Bit 15 to be set After testing your code in RAM and making sure it is bug free the following operations should be performed to transfer it to Flash memory 1 Ensure the name of the top level word in the source code text file the one that runs the whole program is MAIN 2 Clear the RAM by pressing the Reset button on the processor board or by typing ABORT lt return at the command prompt 3 Type SETFLSH lt return gt at the command prompt This sets a flag so that the compiler knows to create code for Flash memory 4 Send the source code file from the host PC to the FORTHdsPIC host The code is initially loaded into RAM but cannot be run here 5 If no errors appeared on the screen as the program compiled type FLASH lt return gt at the command prompt FLASH has copied the RAM vocabulary and code space to the corresponding Flash memory locations 6 Torun the program Either type MAIN at the prompt to run the program or Press Reset on the
20. not forgetting the spaces and press Return The means Print the result on the console 10 gt 64 3 8 OK 10 gt This simple calculation is equivalent to Print 6 x 4 3 but using Reverse Polish notation instead This format is very efficient on computers which feature temporary data storage in the form of push down or LIFO stacks 6 Running FORTH Programs 6 1 Creating New Words with the Compiler The Command Line Interpreter is great for testing small pieces of Forth code but for a full program incorporating structures such as DO LOOP a compiler is necessary 6 1 1 Generate a Forth source code file Use a basic text editor such as Microsoft Notepad to create a Forth source code or program file Save it on the PC hard disk A Forth program consists of at least one new word definition enclosed by and The simple code example above can be compiled as a new word definition called CALC like this Program 1 Calculator CALC SWAP Note that the numbers are not included When the compiled word CALC is executed it will take the top three items off the parameter stack to work on 6 1 2 Running the Compiler Send the source text file to the FORTHdsPIC compiler Use the appropriate function on the terminal emulator to do this For TeraTerm click on Send file from the File menu and select your file to send FORTHdsPIC just sees the text file as a very long keyboard input any colon
21. ointer 1 from pointer then SPACES Print n Spaces increment pointer String length n Print n characters TYPE Pointer from pointer Used ies Nand with COUNT M FORTHdsPIC User Manual Ven 1 0 W G Marshall 2014 Page 15 System Variables and Stack Word Stack Before Stack After Action Word Stack Before Stack After Action RAM address n TOS value of first TOS address of User CODE Coda pointer l level DO LOOP index RAM add eo TOS address of User 2 TOS Value ot HERE Vocabulary pointer J GEREEST L DO LOOP index RAM address n TOS value of third TOS address of BASE number BASE variable K level KEE index Reset Parameter DECIMAL Set number BASE 10 SP stack pointer to TOS n TOS number of HEX Set number BASE 16 DEPTH items on Parameter stack n Define CONSTANT Define VARIABLE CONSTANT VARIABLE lt name gt value n lt name gt System Commands Word Stack Before Stack After Action Word Stack Before Stack After Action List all ForthdsPIC amp VLIST new User words in ABORT Force system reset RAM Erase all user words in Copy user RAM FORGET RAM from lt name gt FLASH area to user Flash onwards memory area Pointer Execute code at Erase user Flash
22. ovided to which the PICkit 3 programmer may be connected The firmware assumes an external 8MHz crystal is connected 1 Plug the PICkit 3 into the development board using the ICSP header Connect the PICkit 3 to the PC with the USB cable and run MPLAB There may be some upheaval as Windows locates a USB driver the first time Run MPLAB and click on Open in the Project menu Select FORTHdsPIC_DIP MPLAB might complain it can t find some files where it expects to find them It should offer a link to the correct location and all you have to do is accept Generate the object code by clicking on the Build All button Click on the Program button to Flash the dsPIC program memory with the firmware Fig 2 Arduino format development board for PIC24 dsPIC from WIDE HK Features ICSP header for debug programmer and a USB UART bridge chip FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 3 4 Running FORTHdsPIC 4 1 MicroStick Il Development Board Once programmed with the FORTHdSsPIC firmware MPLAB is no longer needed but the USB connection is still required to power the board In order to edit compile and run FORTH code you will need the PC running a terminal emulator USB cable and a UART USB bridge cable 1 Connect the bridge cable to UART Tx Rx and Gnd pins of the header on the MicroStick Pin 1 Black Pin 4 Orange Pin 5 Yellow 2 Plug the other end of the cable into the PC Again there should be a one time searc
23. p MicroStick II Development Board 2 2 Custom Development Board PC with two spare USB sockets loaded with MPLAB IDE and a terminal emulator such as TeraTerm Development board with ICSP header pins Microchip PICkit 3 programmer debug tool FTDI UART USB converter cable If no USB port available P N TTL 232R RPi RS P N 767 6200 FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 2 3 Installing FORTHdsPIC 3 1 MicroStick Il Development Board All that s needed for the one time Flashing of the FORTHdsPIC firmware is the PC with MPLAB the MicroStick and a USB cable The MicroStick has on board programmer debug hardware so no additional equipment is required The firmware uses the dsPIC internal clock oscillator 1 Connect the MicroStick to the PC with the USB cable and run MPLAB There may be some upheaval as Windows locates a USB driver the first time 2 Run MPLAB and click on Open in the Project menu Select FORTHdsPIC_Microstick_xx 3 MPLAB might complain it can t find some files where it expects to find them It should offer a link to the correct location and all you have to do is accept 4 Generate the object code by clicking on the Build All button 5 Click on the Program button to Flash the dsPIC program memory with the firmware 3 2 Custom Development Board For other types of board including new designs an external programmer debug tool will be required A standard Microchip ICSP header should be pr
24. pendix 2 Sample Forth eg E 18 FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 1 1 Introduction Two versions of FORTHdSsPIC are available as Microchip MPLAB IDE 8 92 projects Both are designed to run on a 28 pin DIP package of the dsPIC33FJ digital signal controller series At least 64KBytes of Flash memory and 16KBytes of RAM need to be available One version is set up for the MicroStick 2 development board from Microchip and the other for a third party Arduino format board The main difference is the clock source internal on the MicroStick and 8MHz external crystal on the other In either case the processor clock speed delivers a processor performance of 40MIPS This can be increased to 7OMIPS by using the EP version of the chip The other difference is the need for a PICkit 3 programmer debug tool for the Arduino board the MicroStick has this functionality built in 2 System Requirements Both these versions can run code in a stand alone or embedded mode once the user s Forth code has been compiled and Flashed into program memory But first FORTHdsPIC must be installed on the dsPIC chip via a host PC 2 1 MicroStick Il Development Board PC with two spare USB sockets loaded with MPLAB IDE and a terminal emulator such as TeraTerm Microchip MicroStick II Part No DM330013 2 RS Part No 749 6445 FTDI UART USB converter cable Part No TTL 232R RPi RS Part No 767 6200 MiniUSB USB A cable Fig 1 Microchi
25. rk BM1 8251 usecs OK 10 gt Both versions will run from the keyboard input because the MAIN vocabulary entry remains in the RAM and so it can be found by the Interpreter search Type VLIST to confirm this Notice that the Flash based program takes longer to run than the RAM based code This is because of the increased number of PSV fetches which makes the Flash code about 10 slower When either Flash or RAM based code ends control returns to the command prompt 7 2 Running an Embedded Application in Flash memory An embedded program must auto start from power up and never return to the command prompt However when testing an exit should be provided otherwise the only way to regain control is to connect up MPLAB IDE and force a chip erase FORTHdsPIC will then have to be re Flashed Program 4 Walks until a key is pressed MAIN BEGIN WALK INKEY 0 WHILE REPEAT This code fragment from a robot control program keeps WALK running in a loop until it detects a terminal key has been pressed Program 5 Walks for ever MAIN BEGIN WALK AGAIN This code replaces Program 4 only when the complete program is fully debugged The terminal can now be disconnected FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 12 Appendix 1 FORTHdsPIC Basic Instruction Set Typing VLIST at the command prompt provides a list of FORTH words in two vocabularies Interpreter and Compiler New word definitions will appear in a thir
26. tate on right leg 121 60 DO I 3 SERVO I 4 SERVO 10 WAIT LOOP LEANRIGHTBACK Return left leg to floor 91 60 DO 1 SERVO 10 WAIT LOOP 91 50 DO I 2 SERVO 10 WAIT LOOP STEPRIGHT Move right leg forward LEANLEFT ROTATELEFT LEANLEFTBACK STEPLEFT Move left leg forward LEANRIGHT ROTATERIGHT LEANRIGHTBACK STEP Full step forward STEPRIGHT STEPLEFT WALK Walks until a key is pressed SVOSET HOME BEGIN STEP INKEY O WHILE REPEAT FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 18 Forth Timing Benchmark Program Program 7 FORTH Benchmarks adapted for FORTHdsPIC 40MHz clock HEADINGR CR RAM Benchmarks CR BM1 TIMSET TIMSRT 10001 1 DO SP LOOP TIMSTP CR TIMRD 40 M MOD BM1 SE usecs DROP Multiplier BM2 TIMSET TIMSRT 10001 1 DO 11 1 DO LOOP SP LOOP TIMSTP DO LOOP CR TIMRD 40 M MOD BM2 8 F usecs DROP BM3 TIMSET TIMSRT 10001 1 DO 11 1 DO 9 LOOP SP LOOP TIMSTP Literal CR TIMRD 40 M MOD BM3 8 F D usecs DROP VARIABLE V BM4 TIMSET TIMSRT 10001 1 DO 111 DOV LOOP SP LOOP TIMSTP Variable CR TIMRD 40 M MOD BM4 8 F usecs DROP BM5 TIMSET TIMSRT 10001 1 DO 11 1 DO 9 V LOOP SP LOOP TIMSTP Save variable CR TIMRD 40 M MOD BM5 8 F usecs DROP BM6 TIMSET TIMSRT 10001 1 DO 111 DO V LOOP SP LOOP TIMSTP Read variable CR TIMRD 40 M MOD BM6 8 F usecs DROP 9 CONSTANT C BM7 TIMSET TIM
27. unsigned n r SP to SP signed U n2 rl multiply 2 decrement by 2 n1 x n2 gt rh rl n 2 gt r n r DP to SP signed n r SP to SP absolute M nh division ABS Make positive nl nh nl n gt r In gt r n1 r SP to SP signed nh rh DP to DP absolute MOD n2 rem division amp remainder DABS nl rl Make positive n2 n1 gt r rem nh nl gt rh rl n1 r SP to SP unsigned RAM address SP addition to data U MOD n2 rem division amp remainder n in RAM n2 n1 gt r rem addr n gt addr n rh DP to DP unsigned n rh Sign extend SP to M MOD nh rl division amp remainder S gt D rl DP number nl rem nh nl n gt rh rl rem n gt rh rl a r n r SP to SP signed NEGATE R negate n1 multiply then divide n2 n1 x n2 n gt r nh rh n r SP to SP signed DNEGATE nl rl ina Sa MOD n1 rem multiply then divide n2 n1 x n2 n gt r rem nih rh DP to DP addition DADD a it n1h n1l n2h n2l n2h gt rh rl n2l FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 14 Logic Word Stack Before Stack After Action Word Stack Before Stack After Action nt J Logical AND of TOS n n Bit inversion of
28. y and when it finds the correct entry it picks up the Code Pointer and runs EXECUTE This routine checks the item at the Code Pointer address in this case 2800h to see if it is zero as here indicating a Forth linked list follows The Forth Program Counter PC is saved on the Return Stack and moved on to point to the next item in the list at address 2802h The contents of FORTHdsPIC User Manual Vsn 1 0 W G Marshall 2014 Page 8 this address 2802h is now loaded as a pointer and the data at this address 8CBCh checked to see if it s zero If it is then the whole process from saving and incrementing the PC onwards is repeated until a non zero value is found In our example CALC 8CBCh is the address of the multiply machine code routine which can now be executed Now the actual address of the routine in Program memory is OCBCh so Bit 15 is masked off to enable a computed goto to take place Remember Bit 15 is set to trigger the PSV system so the contents of Program memory location OCBCh can be read as Data Once it has been established that it contains executable machine code Bit 15 is cleared and the code at OCBCh executed instead The code starting at address OCBCh is for the single precision multiply and terminates like all the machine code routines with a jump to the threaded linker NEXT This tiny machine code routine is the heart of the system transferring program execution from one link address to the next
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