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Elite on the BBC Micro

Keyboard: DOKEY_FLIGHT [Elite-A, Parasite]

Name: DOKEY_FLIGHT [Show more] Type: Subroutine Category: Keyboard Summary: Scan for the seven primary flight controls (flight version)
Context: See this subroutine in context in the source code References: This subroutine is called as follows: * Main game loop for flight (Part 5 of 6) calls DOKEY_FLIGHT
.DOKEY_FLIGHT JSR U% \ Call U% to clear the key logger LDA QQ22+1 \ Fetch QQ22+1, which contains the number that's shown \ on-screen during hyperspace countdown BEQ l_open \ If the hyperspace countdown is non-zero, jump to JMP DK4_FLIGHT \ DK4_FLIGHT to skip scanning for primary flight keys, \ and move on to scanning for pause, configuration and \ secondary flight keys .l_open LDA JSTK \ If JSTK is non-zero, then we are configured to use BNE DKJ1 \ the joystick rather than keyboard, so jump to DKJ1 \ to read the joystick flight controls, before jumping \ to DK4 to scan for pause, configuration and secondary \ flight keys LDY #7 \ We're going to work our way through the primary flight \ control keys (pitch, roll, speed and laser), so set a \ counter in Y so we can loop through all 7 .DKL2 JSR DKS1 \ Call DKS1 to see if the KYTB key at offset Y is being \ pressed, and set the key logger accordingly DEY \ Decrement the loop counter BNE DKL2 \ Loop back for the next key, working our way from A at \ KYTB+7 down to ? at KYTB+1 LDA auto \ If auto is 0, then the docking computer is not BEQ DK15 \ currently activated, so jump to DK15 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 #0 \ Set X = 0, so we "press" KY1 below ("?", slow down) LDY INWK+28 \ If the updated acceleration in byte #28 is zero, skip BEQ DK11 \ to DK11 BMI P%+3 \ If the updated acceleration is negative, skip the \ following instruction INX \ The updated acceleration is positive, so increment X \ to 1, so we "press" KY2 below (Space, speed up) STA KY1,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 #0 \ Set X = 0, so we "press" 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%+3 \ If the C flag is clear, skip the following instruction INX \ The C flag is set, i.e. the direction of the updated \ roll counter is negative, so increment X to 1 so we \ "press" 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 KY3,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 #0 \ Set X = 0, so we "press" 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%+3 \ If the C flag is set, skip the following instruction INX \ The C flag is clear, i.e. the direction of the updated \ pitch counter is positive, so increment X to 1 so we \ "press" KY6 below ("S", increase pitch) STA KY5,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 .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 KL+3 \ If the "<" key is being pressed, then call the BUMP2 BEQ P%+5 \ routine to increase the roll rate in X by A JSR BUMP2 LDY KL+4 \ If the ">" key is being pressed, then call the REDU2 BEQ P%+5 \ routine to decrease the roll rate in X by A, taking JSR REDU2 \ 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 KL+5 \ If the "X" key is being pressed, then call the REDU2 BEQ P%+5 \ routine to decrease the pitch rate in X by A, taking JSR REDU2 \ the keyboard auto re-centre setting into account LDY KL+6 \ If the "S" key is being pressed, then call the BUMP2 BEQ P%+5 \ routine to increase the pitch rate in X by A JSR BUMP2 STX JSTY \ Store the updated roll rate in JSTY \ Fall through into DK4_FLIGHT to scan for other keys