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Elite on the BBC Micro

Keyboard: DOKEY (Master version)

Name: DOKEY [View in context] Type: Subroutine [Compare versions] Category: Keyboard Summary: Scan for the seven primary flight controls Deep dive: The key logger The docking computer
Scan for the seven primary flight controls (or the equivalent on joystick), pause and configuration keys, and secondary flight controls, and update the key logger accordingly. Specifically: * If we are on keyboard configuration, clear the key logger and update it for the seven primary flight controls, and update the pitch and roll rates accordingly. * If we are on joystick configuration, clear the key logger and jump to DKJ1, which reads the joystick equivalents of the primary flight controls. Both options end up at DK4 to scan for other keys, beyond the seven primary flight controls.
.DOKEY JSR RDKEY-1 \ Scan the keyboard for a key press and return the \ ASCII code of the key pressed in X LDA auto \ If auto is 0, then the docking computer is not BEQ DK16 \ currently activated, so jump to DK16 to skip the \ docking computer manoeuvring code below .auton JSR ZINF \ Call ZINF to reset the INWK ship workspace LDA #96 \ Set nosev_z_hi = 96 STA INWK+14 ORA #%10000000 \ Set sidev_x_hi = -96 STA INWK+22 STA TYPE \ Set the ship type to -96, so the negative value will \ let us check in the DOCKIT routine whether this is our \ ship that is activating its docking computer, rather \ than an NPC ship docking LDA DELTA \ Set the ship speed to DELTA (our speed) STA INWK+27 JSR DOCKIT \ Call DOCKIT to calculate the docking computer's moves \ and update INWK with the results \ We now "press" the relevant flight keys, depending on \ the results from DOCKIT, starting with the pitch keys LDA INWK+27 \ Fetch the updated ship speed from byte #27 into A CMP #22 \ If A < 22, skip the next instruction BCC P%+4 LDA #22 \ Set A = 22, so the maximum speed during docking is 22 STA DELTA \ Update DELTA to the new value in A LDA #&FF \ Set A = &FF, which we can insert into the key logger \ to "fake" the docking computer working the keyboard LDX #15 \ Set X = 0, so we "press" KY+15, i.e. KY1, below \ ("?", slow down) LDY INWK+28 \ If the updated acceleration in byte #28 is zero, skip BEQ DK11 \ to DK11 BMI P%+4 \ If the updated acceleration is negative, skip the \ following instruction LDX #11 \ Set X = 11, so we "press" KY+11, i.e. KY2, with the \ next instruction (Space, speed up) STA KL,X \ Store &FF in either KY1 or KY2 to "press" the relevant \ key, depending on whether the updated acceleration is \ negative (in which case we "press" KY1, "?", to slow \ down) or positive (in which case we "press" KY2, \ Space, to speed up) .DK11 \ We now "press" the relevant roll keys, depending on \ the results from DOCKIT LDA #128 \ Set A = 128, which indicates no change in roll when \ stored in JSTX (i.e. the centre of the roll indicator) LDX #13 \ Set X = 13, so we "press" KY+13, i.e. KY3, below \ ("<", increase roll) ASL INWK+29 \ Shift ship byte #29 left, which shifts bit 7 of the \ updated roll counter (i.e. the roll direction) into \ the C flag BEQ DK12 \ If the remains of byte #29 is zero, then the updated \ roll counter is zero, so jump to DK12 set JSTX to 128, \ to indicate there's no change in the roll BCC P%+4 \ If the C flag is clear, skip the following instruction LDX #14 \ The C flag is set, i.e. the direction of the updated \ roll counter is negative, so set X to 14 so we \ "press" KY+14. i.e. KY4, below (">", decrease roll) BIT INWK+29 \ We shifted the updated roll counter to the left above, BPL DK14 \ so this tests bit 6 of the original value, and if it \ is is clear (i.e. the magnitude is less than 64), jump \ to DK14 to "press" the key and leave JSTX unchanged LDA #64 \ The magnitude of the updated roll is 64 or more, so STA JSTX \ set JSTX to 64 (so the roll decreases at half the \ maximum rate) LDA #0 \ And set A = 0 so we do not "press" any keys (so if the \ docking computer needs to make a serious roll, it does \ so by setting JSTX directly rather than by "pressing" \ a key) .DK14 STA KL,X \ Store A in either KY3 or KY4, depending on whether \ the updated roll rate is increasing (KY3) or \ decreasing (KY4) LDA JSTX \ Fetch A from JSTX so the next instruction has no \ effect .DK12 STA JSTX \ Store A in JSTX to update the current roll rate \ We now "press" the relevant pitch keys, depending on \ the results from DOCKIT LDA #128 \ Set A = 128, which indicates no change in pitch when \ stored in JSTX (i.e. the centre of the pitch \ indicator) LDX #6 \ Set X = 6, so we "press" KY+6, i.e. KY5, below \ ("X", decrease pitch) ASL INWK+30 \ Shift ship byte #30 left, which shifts bit 7 of the \ updated pitch counter (i.e. the pitch direction) into \ the C flag BEQ DK13 \ If the remains of byte #30 is zero, then the updated \ pitch counter is zero, so jump to DK13 set JSTY to \ 128, to indicate there's no change in the pitch BCS P%+4 \ If the C flag is set, skip the following instruction LDX #8 \ Set X = 6, so we "press" KY+8, i.e. KY6, with the next \ instruction ("S", increase pitch) STA KL,X \ Store 128 in either KY5 or KY6 to "press" the relevant \ key, depending on whether the pitch direction is \ negative (in which case we "press" KY5, "X", to \ decrease the pitch) or positive (in which case we \ "press" KY6, "S", to increase the pitch) LDA JSTY \ Fetch A from JSTY so the next instruction has no \ effect .DK13 STA JSTY \ Store A in JSTY to update the current pitch rate IF _COMPACT JMP DK15 \ Jump to DK15 to skip reading the joystick, as this is \ a Master Compact that doesn't support an analogue \ joystick (instead it supports a digital joystick, \ which is read elsewhere) ENDIF .DK16 LDA JSTK \ If JSTK is zero, then we are configured to use the BEQ DK15 \ keyboard rather than the joystick, so jump to DK15 to \ skip reading the joystick IF _SNG47 LDA ADCH1 \ Fetch the high byte of the joystick X value EOR JSTE \ The high byte A is now EOR'd with the value in \ location JSTE, which contains &FF if both joystick \ channels are reversed and 0 otherwise (so A now \ contains the high byte but inverted, if that's what \ the current settings say) ORA #1 \ Ensure the value is at least 1 STA JSTX \ Store the resulting joystick X value in JSTX LDA ADCH2 \ Fetch the high byte of the joystick Y value EOR #&FF \ This EOR is used in conjunction with the EOR JSTGY \ below, as having a value of 0 in JSTGY means we have \ to invert the joystick Y value, and this EOR does \ that part EOR JSTE \ The high byte A is now EOR'd with the value in \ location JSTE, which contains &FF if both joystick \ channels are reversed and 0 otherwise (so A now \ contains the high byte but inverted, if that's what \ the current settings say) EOR JSTGY \ JSTGY will be 0 if the game is configured to reverse \ the joystick Y channel, so this EOR along with the \ EOR #&FF above does exactly that STA JSTY \ Store the resulting joystick Y value in JSTY LDA VIA+&40 \ Read 6522 System VIA input register IRB (SHEILA &40) AND #%00010000 \ Bit 4 of IRB (PB4) is clear if joystick 1's fire \ button is pressed, otherwise it is set, so AND'ing \ the value of IRB with %10000 extracts this bit BNE DK4 \ If the joystick fire button is not being pressed, \ jump to DK4 to scan for other keys LDA #&FF \ Update the key logger at KY7 to "press" the "A" (fire) STA KY7 \ button BNE DK4 \ Jump to DK4 to scan for other keys (this BNE is \ effectively a JMP as A is never 0) ELIF _COMPACT JSR RDJOY \ Call RDJOY to read from either the analogue or digital \ joystick BCC DK4 \ If we just read from the analogue joystick, the C flag \ will be clear, so jump to DK4 to scan for other keys \ Otherwise we just read the digital joystick, so we now \ update the pitch and roll ENDIF .DK15 LDX JSTX \ Set X = JSTX, the current roll rate (as shown in the \ RL indicator on the dashboard) LDA #7 \ Set A to 7, which is the amount we want to alter the \ roll rate by if the roll keys are being pressed LDY KY3 \ If the "<" key is not being pressed, skip the next BEQ P%+5 \ instruction JSR BUMP2 \ The "<" key is being pressed, so call the BUMP2 \ routine to increase the roll rate in X by A LDY KY4 \ If the ">" key is not being pressed, skip the next BEQ P%+5 \ instruction JSR REDU2 \ The "<" key is being pressed, so call the REDU2 \ routine to decrease the roll rate in X by A, taking \ the keyboard auto re-centre setting into account STX JSTX \ Store the updated roll rate in JSTX ASL A \ Double the value of A, to 14 LDX JSTY \ Set X = JSTY, the current pitch rate (as shown in the \ DC indicator on the dashboard) LDY KY5 \ If the "X" key is not being pressed, skip the next BEQ P%+5 \ instruction JSR REDU2 \ The "X" key is being pressed, so call the REDU2 \ routine to decrease the pitch rate in X by A, taking \ the keyboard auto re-centre setting into account LDY KY6 \ If the "S" key is not being pressed, skip the next BEQ P%+5 \ instruction JSR BUMP2 \ The "S" key is being pressed, so call the BUMP2 \ routine to increase the pitch rate in X by A STX JSTY \ Store the updated roll rate in JSTY \ Fall through into DK4 to scan for other keys