Use the VS1053b chip

Massive cleanup has to be done, code has to be tried. Here's an info dump straight from discord

normally, let's assume we begin with a playback of a MP3, you read the file and you will need to dump like a 2K in before it tells you to stop. But, the FIFO inside the FPGA is also 2K, so in theory before things get ugly, you can upload in the MP3 playback system 2K+2K bytes, which ought to be enough to get it going. Now, if you monitor the FPGA FIFO info when empty you can put more in. Normally, after the VS1053 queue is full, it only need 32 bytes at the time and the FPGA takes care of that. Now, basically need to make sure the FPGA FIFO is topped off. Now, when come to end, you will need to fill extra bytes with 00 to empty the VS1053 Fifo and then the tune will end.

Now, the tricky parts is when one needs to stop the sound, there is also a process of filling the FIFO with 00 to cleanse the MP3 pipe. The specs talks about that.

This is as far as I went, now, I believe that if someone wants to play oggs and shit like that the controller need to be updated with new code since there are some issues in the latest tape out of the chip because remember people this is a DSP that actually can be programmed. There is actually an app note on how to use it to come out with Histogramic data (VUE bar app, with small LCD? anybody picking up on that? LOL) for one's pleasure

This is in a nutshell the process to playback stuff. Here is the Register File Details for the VS1053 interface:

$D700..$D707

   case( CPU_A_i[2:0] )
       3'b000: begin CPU_D_o = {Busy, VS1053B_Registers[0][6:0]}; end 
       3'b001: begin CPU_D_o = VS1053B_Registers[1]; end 
       3'b010: begin CPU_D_o = VS1053B_Command_Read[7:0]; end 
       3'b011: begin CPU_D_o = VS1053B_Command_Read[15:8]; end 
       3'b100: begin CPU_D_o = Data_FIFO_Count[7:0]; end
       3'b101: begin CPU_D_o = {VS1053B_FIFO_Empty, VS1053B_FIFO_Full, 3'b000, Data_FIFO_Count[10:8]}; end
       3'b110: begin CPU_D_o = 8'h00; end 
       3'b111: begin CPU_D_o = 8'h00; end
   endcase

VS1053B_Registers[0] - Bit Fields: ($D700..$D703)

[0] 1: Start Transfer

[1] 1: Read Register, 0: Write Register

[7] 1: SPI Transfer in Progress [Busy]

VS1053B_Registers[1]

[3:0] Register to Address

VS1053B_Registers[2] Data Access Low

VS1053B_Registers[3] Data Access Hi

There are 2 Accessible Area for the VS1053 The Control/Register Section with 16bits wide Data and 16 Addresses (See specs) The Other is the Data(Stream) Port, there is no Address and it is 8bits

When one wants to control the chip, one need to setup the address and data (for write) and address for read, one needs to setup the direction and when everything is ready, one needs to trigger the transaction. When one needs to write file data for playback, one needs only to write data to FIFO port @ $D704 and monitor FIFO @ $D705/$D706 Here is a piece of code, not the best, prolly not the most kosher either, but that ought to get you started. I am simply playing back a very tiny sound effect (small enough to fit in the memory so not much to play back)

MP3_Playing:

               lda #$42
               sta $d702   ; Set the Stream mode
               lda #$48
               sta $d703
               lda #$21    ; Start Transaction
               sta $d700
               lda #$20    ; Return to Zero
               sta $d700 

lda #$00

sta $d702

sta $d703

lda #$23  ; Go read the Command Register

sta $d700

lda $d702

lda $d703

               ldx #$00

VS_Pause:

               inx 
               cpx #$80
               bne VS_Pause

               lda #$80
               sta $00     ; Let's enable the MMU Edit, keep the MMU 00 in play
               lda #$08    ; Bring about the first 8K 
               sta $0D     ; It starts @ $08 == page 0

               setaxl 

               ldx #$0000
               ldy #$0000

Go Fill the FIFO

               setas

MP3_Fill_FIFO: ;lda @l MP3_Music,x

               lda $A000,x
               sta VS1053_STREAM_DATA      ; THere is 2K FIFO
               inx 
               iny 
               cpy #$0800                  ; Fill 2K
               bne MP3_Fill_FIFO

MP3_Fill_FIFO_Wait:

               ldy #$0000
               lda VS1053_FIFO_COUNT_HI    ; Load High Portion is monitor for 
               and #$80
               cmp #$80
               bne MP3_Fill_FIFO_Wait

               cpx #$2000
               bne MP3_Fill_FIFO
               ldx #$0000

               lda $0D
               inc A
               sta $0D 
               cmp #$0c 
               bne MP3_Fill_FIFO

               lda #$05
               sta $0D

MP3_We_are_Done:

               setaxs 
               rts