reading images form file

oled.mac

@@ -7,6 +7,14 @@ LF   EQU  0Ah       ; new line
 BDOS EQU  0005h     ; BDOS entry point
 PSTR EQU  09h       ; print string
 CRED EQU  01h       ; read console
+FOPE EQU  0Fh       ; file open
+FRED EQU  14h       ; file read next record
+
+FCB       EQU  5Ch     ; File Control Block      
+FCBFNAME  EQU  FCB+01h ; FCB File Name 
+FCBEX     EQU  FCB+0Ch ; FCB Excent Number
+FCBRC     EQU  FCB+0Fh ; FCB Record Count
+FCBCR     EQU  FCB+20h ; FCB Current Record
 
 OLED EQU  50h  ; base addr of OLED card
 ORST EQU  04h  ; reset command (H)
@@ -30,16 +38,49 @@ OCOLL EQU  80h  ; column count: 128 columns
 ; MAIN
 CALL OINIT     ; init OLED
 CALL OCLS      ; clear screen
-CALL PROMPT    ; print prompt
-
 CALL OCSTART   ; go to start
-CALL READLINE  ; read row A
-CALL READLINE  ; read row B
-CALL READLINE  ; read row C
-CALL READLINE  ; read row D
 
+LD   A,(FCBFNAME)   ; load first char of file name
+CP   ' '            ; check file name provided
+
+JP   NZ,MAIN1
+CALL PROMPTREAD     ; read from prompt
+RET                 ; exit to CP/M
+
+MAIN1:
+CALL FILEREAD  ; read from file
 RET            ; exit to CP/M
 
+PROMPTREAD:
+     LD   DE,MSGPROMPT
+     CALL PRINT    ; print prompt
+
+     CALL READLINE  ; read row A
+     CALL READLINE  ; read row B
+     CALL READLINE  ; read row C
+     CALL READLINE  ; read row D
+     RET
+
+FILEREAD:
+     LD   DE,MSGFILEREAD
+     CALL PRINT       ; print reading from file
+     XOR  A
+     LD   (FCBEX),A   ; select 0'th extent
+     LD   (FCBRC),A   ; clear
+     LD   C,FOPE      ; open file
+     LD   DE,FCB      ; use default FCB
+     CALL BDOS
+     CP   0FFh        ; is error
+     JP   Z,FILEREAD1
+     XOR  A
+     LD   (FCBCR),A   ; start from beggining
+     CALL READRECORD  ; read 128 byte record
+     RET
+FILEREAD1:
+     LD   DE,MSGOPENERR
+     CALL PRINT
+     LD   A,0FFh
+     RET
 
 READLINE:
      LD   D,OCOLL   ; number of columns
@@ -52,6 +93,21 @@ READLINE1:
      JP   NZ,READLINE1  ; next column
      RET
 
+; reads block using default FCB
+; A=0 - OK
+; A=FFh - error
+READRECORD:
+     LD   C,FRED    ; read file
+     LD   DE,FCB    ; use default FCB
+     CALL BDOS
+     JP   NZ,READRECORD1
+     RET
+READRECORD1:
+     LD   DE,MSGREADERR
+     CALL PRINT
+     LD   A,0FFh    ; error
+     RET
+
 OINIT:
      CALL ORESET    ; reset OLED
      LD   HL,OINITSEQ ; commands to send
@@ -169,15 +225,22 @@ READHEX:
      OR   B         ; OR B to A
      RET
 
-PROMPT:
+; DE - address to $ terminated string
+PRINT:
      LD   C,PSTR    ; load function number
-     LD   DE,PROMPTMSG    ; load string addr
      CALL BDOS      ; call CP/M
      RET
 
-PROMPTMSG: 
+MSGPROMPT: 
      DB   'OLED:>', CR, LF,'$' ; string terminated with $
 
+MSGFILEREAD:
+     DB   'Reading from file', CR, LF, '$'
+MSGOPENERR:
+     DB   'Error opening file', CR, LF, '$'
+MSGREADERR:
+     DB   'Error reading file', CR, LF, '$'
+
 ; Initialization sequence
 ; 081h,080h - set contrast (080h full)
 ; 020h,000h - set horizontal window wrapping