; ******************************************************************* ; DTMF decoder implemented using the Goertzel algorithm. ; Electronics IV (Honours) Project 1994 ; by Steven J. Merrifield ; ; This program incorporates changes made after the original thesis ; was submitted. Where there are discrepancies between this, and the ; original code, the code presented here should take precedence. ; ******************************************************************* .sect "VECTORS" b start ; 0 - External reset b INT0 ; 2 - User int 0 b INT1 ; 4 - User int 1 b INT2 ; 6 - User int 2 b d_int ; 8 - Reserved b d_int ; 10 - Reserved b d_int ; 12 - Reserved b d_int ; 14 - Reserved b d_int ; 16 - Reserved b d_int ; 18 - Reserved b d_int ; 20 - Reserved b d_int ; 22 - Reserved b tim_int ; 24 - Internal timer b rx_int ; 26 - Serial port rx b tx_int ; 28 - Serial port tx b d_int ; 30 - Trap instruction addr. .text ; IO ports LED0 .set 0 LED1 .set 1 LED2 .set 2 LED3 .set 3 u_data .set 4 u_ctrl .set 5 ; Page 0 variables (0000h) drr .set 0 ; data rx reg. address dxr .set 1 ; data tx reg. address imr .set 4 ; interrupt mask reg. tx_flag .set 96 ; data has been sent flag rx_flag .set 97 ; data has been received flag stat_st .set 98 ; temp for saving status reg. during subroutine calls accl_st .set 99 ; temp for low half of accumulator acch_st .set 100 ; temp for high half of accumulator rx_data .set 101 ; received data is stored here tx_data .set 102 ; data to be transmitted must be stored here init_data .set 105 ; data for initialisation muse be stored here init_flag .set 106 ; flag for secondary communications (initialisation) OFF .set 107 ; data to turn LED off ON .set 108 ; data to turn LED on stat_1 .set 109 ; save status register 1 nfilt .set 8 ; No. of filters (one for each row/col freq) u_data .set 4 u_ctrl .set 5 dram .set 0200h ; DRAM starts at addr. 0200h (ie DP = 4) cs1 .set dram+00 cs2 .set dram+01 cs3 .set dram+02 cs4 .set dram+03 cs5 .set dram+04 cs6 .set dram+05 cs7 .set dram+06 cs8 .set dram+07 negmax .set dram+08 rowmx .set dram+11 colmx .set dram+12 rowmax .set dram+13 colmax .set dram+14 count .set dram+15 rowcol .set dram+16 last .set dram+19 sec_last .set dram+20 dat11 .set dram+28 dat23 .set dram+33 dat14 .set dram+34 dat15 .set dram+36 dat17 .set dram+40 dat27 .set dram+41 dat18 .set dram+42 dat28 .set dram+43 dat29 .set dram+45 dat213 .set dram+53 dat216 .set dram+59 datin .set dram+60 temp .set dram+61 temp2 .set dram+62 temp3 .set dram+63 save_acc .set dram+64 prnt .set dram+65 test .set dram+66 ; Filter co-efficients for each row/col. frequency ; Fundamental - Real coeff N=205 tblstrt .word 27906 ; 697 Hz .word 26802 ; 770 Hz .word 25597 ; 851 Hz .word 24295 ; 941 Hz .word 19057 ; 1209 Hz .word 15654 ; 1336 Hz .word 12945 ; 1477 Hz .word 09166 ; 1633 Hz tblend .word 08000h ; NegMax - mask for data out ; ******************************************************************* ; Initialization ; ******************************************************************* start ldpk 0 ; Point to data page zero fort 0 ; Set serial port to be 16 bits wide rtxm ; External sync sfsm ; Sync required for each transfer cnfd ; Set block B0 to be data memory sovm ; set overflow mode ssxm ; set sign extention mode zac ; Reset tx and rx flags sacl tx_flag sacl rx_flag sacl init_flag sacl OFF lalk 1 sacl ON eint lalk 020h ; Enable only tx interrupt to init AIC sacl imr lalk 1223h ; setup TA and RA sacl init_data call tx_ready lalk 1 sacl init_flag wait_2nd_a lac init_flag ; wait until secondary comms is finished bnz wait_2nd_a lalk 468eh ; setup TB and RB sacl init_data call tx_ready lalk 1 sacl init_flag wait_2nd_b lac init_flag ; wait until secondary comms is finished bnz wait_2nd_b lalk 010h ; enable only rx int for receiveing data sacl imr ; *********************************************** ; Execution starts here ; *********************************************** ldpk 4 ; Point to data page 4 (0200h) larp ar0 lrlk ar0,cs1 ; Pointer to the start of ram to be ; initialised. lalk tblstrt ; Pointer to the start of init table. lrlk ar1,tblend-tblstrt ; Count of data to be moved. next tblr *+,ar1 addk 1 banz next,*-,ar0 lalk 0ffh ; set last and second last decoded sacl last ; digits to be "invalid" sacl sec_last again zac ; Zero DFT loop variables lrlk 0,15 lrlk 1,dat11 zero larp 1 sacl *+,0,0 banz zero ; *********************************************** ; Take data and calculate DFT loop ; *********************************************** lalk 205 ; Set DFT loop variable loop sacl count lrlk ar0,cs8 ; Set up pointer to co-efficients. lrlk ar1,dat28 ; Set up pointer to delayed outputs. lrlk ar2,nfilt-1 ; Number of filters. ; read from AIC under interrupts ldpk 0 call rx_ready lac rx_data ldpk 4 sfr ; Stop accumulator from overflowing by shifting sfr ; data to the right - this effectively takes the ; sfr ; 16 bit value read from the serial port and converts ; sfr ; it to a 14 bit value as generated by the AIC. ; My hardware has an amplifier which limits the gain ; of the input, so only two shifts are required. When ; run in the simulator, all four shifts are needed. sacl datin ; *********************************************** ; Begin DFT loops ; *********************************************** frpt larp ar0 lt *,ar1 ; load cos(8*C) ready for multiply lac datin,12 ; X(n) subh *- ; X(n) - Y(n-2) mpy * ; cos(8*C) * Y(n-1) ltd * ; Y(n-1) -> Y(n-2) apac apac apac ; X(n) + 2cos(8*C) * Y(n-1) - Y(n-2) sach *-,0,ar0 ; --> Y(n-1) bv overflow mar *-,ar2 ; Decrement the co-efficient pointer. banz frpt,*-,ar0 ; Decrement the filter number. lac count ; Repeat for length of transform subk 1 bnz loop b check overflow out OFF,LED0 ; Show overflow status on LED0 ; *********************************************** ; Calculate energy at each frequency ; *********************************************** check lrlk 0,cs8 lrlk 1,dat28 lrlk 2,nfilt-1 maglp call energy sach *-,1,ar0 mar *-,ar2 banz maglp,*-,ar0 ; *********************************************** ; Compare energies and determine decode value ; *********************************************** lalk 3 sacl rowmx sacl colmx ; *********************************************** ; Find row peak ; *********************************************** rows lrlk 1,2 lrlk 0,dat23 lac dat14 sacl rowmax rowl larp 0 mar *- lac rowmax sub * bgez rowbr sar 1,rowmx lac * sacl rowmax rowbr mar *-,1 banz rowl ; *********************************************** ; Find column peak ; *********************************************** column lrlk 1,2 lrlk 0,dat27 lac dat18 sacl colmax coll larp 0 mar *- lac colmax sub * bgez colbr sar 1,colmx lac * sacl colmax colbr mar *-,1 banz coll ; *********************************************** ; Merge row / column together ; *********************************************** lac rowmx,4 or colmx sacl rowcol ; *********************************************** ; Check for valid signal strength ; *********************************************** sig_str lac colmax subk 4 blz invalid_dig lac rowmax subk 4 blz invalid_dig b test_new invalid_dig lalk 0ffh sacl rowcol ; *********************************************** ; Test if the decoded digit is new ; *********************************************** test_new lac rowcol sub last bz samelast lac last sacl sec_last lac rowcol sacl last b again samelast lac rowcol sub sec_last bz again lac last sacl sec_last lac rowcol sacl last ; check if decoded digit == 0 (my TC prog can't read an ASCII null) lac rowcol subk 0 bnz check_u addk 55h sacl rowcol check_u in temp,u_ctrl ; wait until TxRdy bit temp,15 bbz check_u out rowcol,u_data ; send decoded digit to PC b again ; get next sample ; *********************************************** ; Energy calculation subroutine ; *********************************************** energy lac negmax,15 ; NegMax = 8000h add *,15,1 sach count lt *- ; -1/2 + CSn/2 mpy count pac sach count,1 ; D2(CSn-1)/2 lt *+ mpy count pac sach count,1 ; D1 * D2(CSn-1)/2 lac *-,15 sub *,15 abs sach * ; abs(D2-D1)/2 lt * mpy * pac ; ((D2-D1)/2)^2 sub count,15 ; ((D2-D1)^2)/4 - D1*D2(CSn-1)/2 ret ; ******************************************************************* ; Test if receive flag is set ; ******************************************************************* rx_ready ldpk 0 lac rx_flag andk 00ffh subk 0ffh bnz rx_ready sacl rx_flag ret ; ******************************************************************* ; Test if transmit flag is set ; ******************************************************************* tx_ready ldpk 0 lac tx_flag andk 00ffh subk 0ffh bnz tx_ready sacl tx_flag ret ; ******************************************************************* ; Receive interrupt service routine ; ******************************************************************* rx_int sst stat_st ; Push status register ldpk 0 sst1 stat_1 sacl accl_st ; Push accumulator sach acch_st lalk 0ffh ; Set received data flag sacl rx_flag lac drr ; Get data from AIC sacl rx_data ; Save it to memory zals accl_st ; Pop accumulator addh acch_st lst1 stat_1 lst stat_st ; Pop status register eint ret ; ******************************************************************* ; Transmit interrupt service routine ; ******************************************************************* tx_int sst stat_st ; Push status reg ldpk 0 sst1 stat_1 sacl accl_st ; Push accumulator sach acch_st bit init_flag,14 bbz test_2nd send_2nd lac init_data sacl dxr zac sacl init_flag b exit_tx_int test_2nd bit init_flag,15 bbnz send_1st primary lalk 0ffh ; Set transmit data flag sacl tx_flag lac tx_data ; Get data from memory andk 0fffch ; Mask out bottom 2 bits sacl dxr ; Write data to AIC b exit_tx_int send_1st rxf lac init_flag addk 1 sacl init_flag lalk 03 sacl dxr exit_tx_int zals accl_st ; Pop accumulator addh acch_st lst1 stat_1 lst stat_st ; Pop status reg eint ret ; ******************************************************************* ; Interrupts we're not interested in ; ******************************************************************* d_int ret tim_int ret int0 ret int1 ret int2 ret .end