旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴커 � Programming the SoundBlaster DSP � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸 Written for the PC-GPE by Mark Feldman e-mail address : u914097@student.canberra.edu.au myndale@cairo.anu.edu.au 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � THIS FILE MAY NOT BE DISTRIBUTED � � SEPARATE TO THE ENTIRE PC-GPE COLLECTION. � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� 旼컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Disclaimer � 읕컴컴컴컴컴켸 I assume no responsibility whatsoever for any effect that this file, the information contained therein or the use thereof has on you, your sanity, computer, spouse, children, pets or anything else related to you or your existance. No warranty is provided nor implied with this information. 旼컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Introduction � 읕컴컴컴컴컴컴켸 The SoundBlaster is capable of both FM and digitised sounds. The FM wave is fully Adlib compatible, so check the ADLIB.TXT file for info on how to program it. This file will concentrate on recording and playback of digital samples through the SoundBlaster CT-DSP 1321 chip. 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � The SoundBlaster DSP I/O Ports � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸 The DSP (Digital Sound Processor) chip is programmed through 4 ports which are determined by the SoundBlaster base address jumper setting: RESET 2x6h READ DATA 2xAh WRITE COMMAND/DATA output WRITE BUFFER STATUS input 2xCh DATA AVAILABLE 2xEh where x = 1 for base address jumper setting 210h x = 2 for base address jumper setting 220h . . x = 6 for base address jumper setting 260h 旼컴컴컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Resetting the DSP � 읕컴컴컴컴컴컴컴컴컴� You have to reset the DSP before you program it. This is done with the following procedure : 1) Write a 1 to the SoundBlaster RESET port (2x6h) 2) Wait for 3 micro-seconds 3) Write a 0 to the SoundBlaster RESET port (2x6h) 4) Read the byte from the DATA AVAILABLE (2xEh) port until bit 7 = 1 5) Poll for a ready byte (AAh) from the READ DATA port (2xAh). Before reading the READ DATA port it is avdvisable. The DSP usually takes somewhere around 100 micro-seconds to reset itself. If it fails to do within a reasonable time (say 200 micro-seconds) then an error has occurred, possibly an incorrect I/O address is being used. 旼컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Writing to the DSP � 읕컴컴컴컴컴컴컴컴컴켸 A value can be written to the DSP with the following procedure : 1) Read the DSP's WRITE BUFFER STATUS port (2xCh) until bit 7 = 0 2) Write the value to the WRITE COMMAND/DATA port (2xCh) 旼컴컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Reading the DSP � 읕컴컴컴컴컴컴컴컴� A value can be read from the DSP with the following procedure : 1) Read the DSP's DATA AVAILABLE port (2xEh) until bit 7 = 1 2) Read the data from the READ DATA port (2xAh) 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Turning the speaker on and controlling DMA � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸 Speaker and DMA control are handled by writing one of the following bytes to the DSP: 旼컴컴컴컴컴컴컴컴컴컴컴컴� � Value Description � 쳐컴컴컴컴컴컴컴컴컴컴컴컴� � D0h DMA Stop � � D1h Turn speaker on � � D3h Turn speaker off � � D4h DMA Continue � 읕컴컴컴컴컴컴컴컴컴컴컴컴� DMA is discussed below. The DMA commands shown here can be used to pause the sample during DMA playback playback. 旼컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Writing to the DAC � 읕컴컴컴컴컴컴컴컴컴켸 The DAC (Digital to Analog Converter) is the part of the card which converts a sample number (ie 0 -> 255) to a sound level. To generate a square sound wave at maximum volume (for example) you could alternate writing 0's and 255's to the DAC. Programming the DAC in direct mode involves the main program setting the DAC to a desired value. Only 8 bit DAC is available in direct mode. To set the DAC level you write the value 10h to the DSP followed by the sample number (0 -> 255). Note that no sound will be heard unless the speaker has been turned on. In direct mode the main program is responsible for the timing between samples, the DAC can output sound samples as fast as the calling program can change it. Typically the timer interrupt is reprogrammed and used to generate the timing required for a sample playback. Info on programming the PIT chip can be found in the PIT.TXT file. The DAC can also be programmed to accept values sent to it via the DMA chip. Draeden has written an excellent article on programming the DMA chip (see DMA_VLA.TXT) so only a brief example of it's use will be given here. The important thing to remember is that the DMA chip cannot transfer data which crosses between page breaks. If the data does cross page breaks then it will have to be split up into several transfers, with one page per transfer. Setting the playback frequency for the DMA transfer is done by writing the value 40h to the DSP followed by TIME_CONSTANT, where TIME_CONSTANT = 256 - 1000000 / frequency There are several types of DMA transfers available. The following table lists them: 旼컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴커 쿏MA_TYPE_VALUE Description Frequency Range � 쳐컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴캑 � 14h 8 bit 4KHz -> 23 KHz � � 74h 4 bit ADPCM 4KHz -> 12 KHz � � 75h 4 bit ADPCM with 4KHz -> 12 KHz � � reference byte � � 76h 2.6 bit ADPCM 4KHz -> 13 KHz � � 77h 2.6 bit ADPCM with 4KHz -> 13 KHz � � reference byte � � 16h 2 bit ADPCM 4KHz -> 11 KHz � � 17h 2 bit ADPCM with 4KHz -> 11 KHz � � reference byte � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸 ADPCM stands for Adaptive Pulse Code Modulation, a sound compression technique where the difference between successive samples is stored rather than their actual values. In the modes with reference bytes, the first byte is the actual starting value. Having modes with and without reference bytes means you can output successive blocks without the need for a reference byte at the start of each one. The procedure for doing a DMA transfer is as follows: 1) Load the sound data into memory 2) Set up the DMA chip for the tranfer 3) Set the DSP TIME_CONSTANT to the sampling rate 4) Write DMA_TYPE_VALUE value to the DSP 5) Write DATA_LENGTH to the DSP (2 bytes, LSB first) where DATA_LENGTH = number of bytes to send - 1 Note that the DMA chip must be programmed before the BSP. 旼컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Reading from the ADC � 읕컴컴컴컴컴컴컴컴컴컴켸 Reading samples from the ADC (Analog to Digital Converter) can also be done in either direct or DMA mode. To read a sample in direct mode write the value 20h to the DSP and then read the value from the DSP. Simple as that! To set up the DSP for a DMA transfer, follow this procedure : 1) Get a memory buffer ready to hold the sample 2) Set up the DMA chip for the transfer 3) Set the DSP TIME_CONSTANT to the sampling rate 4) Write the value 24h to the DSP 5) Write DATA_LENGTH to the DSP (2 bytes, LSB first) where DATA_LENGTH = number of bytes to read - 1 Note that the DMA chip must be programmed before the BSP. DMA reads only support 8 bit mode, compressed modes are done by software and stored in the voc file. I haven't tried to figure out how the compression is done. If someone does figure it out I'd like to know about it! 旼컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � Programming the DMA Chip � 읕컴컴컴컴컴컴컴컴컴컴컴컴켸 As mentioned before, Draeden has written a very good article on the dma chip, but here is a brief run down on what you would need to do to program the DMA channel 1 for the DSP in real mode: 1) Calculate the 20 bit address of the memory buffer you are using where Base Address = Segment * 16 + Offset eg 1234h:5678h = 179B8h 2) Send the value 05h to port 0Ah (mask off channel 1) 3) Send the value 00h to port 0Ch (clear the internal DMA flip/flop) 4) Send the value 49h to port 0Bh (for playback) or 45h to port 0Bh (for recording) 5) Write the LSB (bits 0 -> 7) of the 20 bit memory address to port 02h 6) Write the MSB (bits 8 -> 15) of the 20 bit memory address to ort 02h 7) Write the Page (bits 16 -> 19) of the 20 bit memory address to port 83h 8) Send the LSB of DATA_LENGTH to port 03h 9) Send the MSB of DATA_LENGTH to port 03h 10) Send the value 01h to port 0Ah (enable channel 1) 旼컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � End of DMA Interrupt � 읕컴컴컴컴컴컴컴컴컴컴켸 When a DMA transfer is complete an interrupt is generated. The actual interrupt number depends on the SoundBlaster card's IRQ jumper setting: 旼컴컴컴컴컴컴컴컴컴컴컴커 � IRQ Jumper � � Setting Interrupt � 쳐컴컴컴컴컴컴컴컴컴컴컴캑 � 2 0Ah � � 3 0Bh � � 5 0Dh � � 7 0Fh � 읕컴컴컴컴컴컴컴컴컴컴컴켸 To service one of these interrupts you must perform these 3 tasks: 1) Acknowledge the DSP interrupt by reading the DATA AVAILABLE port (2xEh) once. 2) If there are more blocks to transfer then set them up 3) Output value 20h (EOI) to the interrupt controller port 20h Of course, as with any hardware interrupt you must also leave the state of the system (registers etc..) the way it was when the interrupt was called. 旼컴컴컴컴컴컴컴컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 � A Simple DSP Pascal Unit � 읕컴컴컴컴컴컴컴컴컴컴컴컴켸 { DSP.PAS - A demo SoundBlaster DSP unit for real mode By Mark Feldman } Unit DSP; Interface { ResetDSP returns true if reset was successful base should be 1 for base address 210h, 2 for 220h etc... } function ResetDSP(base : word) : boolean; { Write DAC sets the speaker output level } procedure WriteDAC(level : byte); { ReadDAC reads the microphone input level } function ReadDAC : byte; { SpeakerOn connects the DAC to the speaker } function SpeakerOn: byte; { SpeakerOff disconnects the DAC from the speaker, but does not affect the DAC operation } function SpeakerOff: byte; { Functions to pause DMA playback } procedure DMAStop; procedure DMAContinue; { Playback plays a sample of a given size back at a given frequency using DMA channel 1. The sample must not cross a page boundry } procedure Playback(sound : Pointer; size : word; frequency : word); Implementation Uses Crt; var DSP_RESET : word; DSP_READ_DATA : word; DSP_WRITE_DATA : word; DSP_WRITE_STATUS : word; DSP_DATA_AVAIL : word; function ResetDSP(base : word) : boolean; begin base := base * $10; { Calculate the port addresses } DSP_RESET := base + $206; DSP_READ_DATA := base + $20A; DSP_WRITE_DATA := base + $20C; DSP_WRITE_STATUS := base + $20C; DSP_DATA_AVAIL := base + $20E; { Reset the DSP, and give some nice long delays just to be safe } Port[DSP_RESET] := 1; Delay(10); Port[DSP_RESET] := 0; Delay(10); if (Port[DSP_DATA_AVAIL] And $80 = $80) And (Port[DSP_READ_DATA] = $AA) then ResetDSP := true else ResetDSP := false; end; procedure WriteDSP(value : byte); begin while Port[DSP_WRITE_STATUS] And $80 <> 0 do; Port[DSP_WRITE_DATA] := value; end; function ReadDSP : byte; begin while Port[DSP_DATA_AVAIL] and $80 = 0 do; ReadDSP := Port[DSP_READ_DATA]; end; procedure WriteDAC(level : byte); begin WriteDSP($10); WriteDSP(level); end; function ReadDAC : byte; begin WriteDSP($20); ReadDAC := ReadDSP; end; function SpeakerOn: byte; begin WriteDSP($D1); end; function SpeakerOff: byte; begin WriteDSP($D3); end; procedure DMAContinue; begin WriteDSP($D4); end; procedure DMAStop; begin WriteDSP($D0); end; procedure Playback(sound : Pointer; size : word; frequency : word); var time_constant : word; page, offset : word; begin SpeakerOn; size := size - 1; { Set up the DMA chip } offset := Seg(sound^) Shl 4 + Ofs(sound^); page := (Seg(sound^) + Ofs(sound^) shr 4) shr 12; Port[$0A] := 5; Port[$0C] := 0; Port[$0B] := $49; Port[$02] := Lo(offset); Port[$02] := Hi(offset); Port[$83] := page; Port[$03] := Lo(size); Port[$03] := Hi(size); Port[$0A] := 1; { Set the playback frequency } time_constant := 256 - 1000000 div frequency; WriteDSP($40); WriteDSP(time_constant); { Set the playback type (8-bit) } WriteDSP($14); WriteDSP(Lo(size)); WriteDSP(Hi(size)); end; end. 旼컴컴컴컴컴컫컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴� � References � 읕컴컴컴컴컴켸 Title : The SoundBlaster Developpers Kit Publishers : Creative Labs Inc Creative Technology PTE LTD Title : Sound Blaster - The Official Book Authors : Richard Heimlich, David M. Golden, Ivan Luk, Peter M. Ridge Publishers : Osborne/McGraw Hill ISBN : 0-07-881907-5 Some of the information in this file was either obtained from or verified by the source code in a public domain library called SOUNDX by Peter Sprenger. I haven't tried using his library yet (I don't have a C compiler at the moment) but it looks very well done and contains numerous sound card detection routines. Says Peter : "It would be nice, that when you make something commercial with my routines, that you send me a copy of your project or send me some bucks, just enough for pizza and coke to support my night programming sessions. If you send me nothing, ok. But USE the stuff, if you can need it!". Heh...a REAL programmer! ftpsite: ftp.uwp.edu directory: /pub/msdos/demos/programming/game-dev/source filename: soundx.zip 旼컴컴컴컴컴컴컴컴쩡컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴 � Sound Familiar? � 읕컴컴컴컴컴컴컴컴� What the...why is there a faint glimmer of sunlight outside? HOLY $#!^!! It's 5:30am! I'm goin' to bed!