Aros/Developer/Docs/Libraries/LowLevel

History

The lowlevel.library, introduced in Workbench/Kickstart 3.1, offers timer and keyboard/joystick support functions to game and demo programmers.

The original library was designed by Commodore and had the following issues...

• Input functions are polling based while AmigaOS is event driven.
• Input functions are system wide, not application based. If left is pressed, it is expected only the active applications detects it. With lowlevel, the others also detect it.
• Some features can only be used by one application at a time. Really a bad idea in a multitasking environment.
• Some other timer function only works for 16 hours. Then it returns wrong results.
• Programmers are invited to use software interruption instead of high priority thread.

lowlevel.library does not maintain a list of interrupt handlers, it maintains only a single interrupt handler, which is added additionally to standard keyboard processing.

Current

ReadJoyPort() is patched for USB usage.

In the original AmigaOS lowlevel.library and keyboard.device are tightly glued together and in fact just two interfaces of one module and can't be separated. Anyway, two new HIDDs which now manages the keyboard and mouse drivers. Now it is possible to plug in several lowlevel drivers at once, their input streams will be merged. See rom/hidd/keyboard and rom/hidd/mouse.

Analogue Programming

ReadJoyPort(unit) to get the usual digital positions ReadJoyPort(unit + JP_TYPE_ANALOGUE) to get the new analog positions which contains two eight bit counters holding the absolute position of two joystick axis.

The analogue axis information is an unsigned integer from 0 to 255 and has not necessarily been calibrated to be centered at 128.

An application can also take control and can explicitly demand JP_TYPE_ANALOGUE data by either adding JP_ANALOGUE_PORT_MAGIC to the portNumber or setting SJA_TYPE to SJA_TYPE_ANALOGUE in SetJoyPortAttrs().

• To use the second analog joy, you must assign it like a second joystick (for example left joy as joy in port 0 and the other in port 1 ) and enable the analog hack on this "second" joypad
• use JP_ANALOGUE_PORT_MAGIC on two lowlevel units. Then you map the second analog stick of your joypad to the axis of lowlevel unit 0
• Your game can now read the two analog sticks of one single joypad :-)

Rumble Programming

SetJoyPortAttrsA() adds three options for force feedback and rumble pack support. These are currently very basic controls of two motors found in the joypad.

• portNumber - the joyport in question (0-3).
• SJA_Type (ULONG) - Sets the current controller type to the mouse, joystick, or game controller. Supply one of SJA_TYPE_GAMECTLR, SJA_TYPE_MOUSE, SJA_TYPE_JOYSTK, or SJA_TYPE_AUTOSENSE. If SJA_TYPE_AUTOSENSE is used, SJA_TYPE_ANALOGUE, or SJA_TYPE_AUTOSENSE.

If SJA_TYPE_AUTOSENSE is used, ReadJoyPort() will attempt to determine the type of controller plugged into the given port automatically. If one of the other types is used, ReadJoyPort() will forcing a port to deallocate any allocated resources; return the implied type to SJA_TYPE_AUTOSENSE.

• SJA_RumbleSetSlowMotor (UBYTE) - If a rumble pack is available, using this tag will set the speed of the slow motor to the given value (0 - 255).
• SJA_RumbleSetFastMotor (UBYTE) - If a rumble pack is available, using this tag will set the speed of the fast motor to the given value (0 - 255).
• SJA_RumbleOff (BOOL) - If set, this will turn the rumble pack motors off.

RESULT success - TRUE if everything went according to plan, or FALSE upon failure

The call to turn rumble on is

SetJoyPortAttrsA(joy, SJA_RumbleSetFastMotor, 255, TAG_DONE);

where joy is the appropriate unit

ReadJoyPort() ignores buttons 8-12 on the gamepad, even though they work fine in Preferences 

Sometimes they are not, as there is no real standard for that. It seems to be the norm but not always...

Examples

#include <proto/exec.h>
#include <proto/dos.h>
#include <proto/lowlevel.h>
#include <libraries/lowlevel_ext.h>

#include <stdio.h>
#include <stdlib.h>


struct Library *LowLevelBase;

static void printbuttons(ULONG val)
{
    if (val & JPF_BUTTON_PLAY)      printf("[PLAY/MMB]");
    if (val & JPF_BUTTON_REVERSE)   printf("[REVERSE]");
    if (val & JPF_BUTTON_FORWARD)   printf("[FORWARD]");
    if (val & JPF_BUTTON_GREEN)     printf("[SHUFFLE]");
    if (val & JPF_BUTTON_RED)       printf("[SELECT/LMB/FIRE]");
    if (val & JPF_BUTTON_BLUE)      printf("[STOP/RMB]");
}

static void printmousedirections(ULONG val)
{
    printf("[%d,%d]", (val & JP_MHORZ_MASK), (val & JP_MVERT_MASK) >> 8);
}

static void printajoydirections(ULONG val)
{
    printf("[%d, %d]", (val & JP_XAXIS_MASK), (val & JP_YAXIS_MASK) >> 8);
}
static void printjoydirections(ULONG val)
{
    if (val & JPF_JOY_UP)       printf("[UP]");
    if (val & JPF_JOY_DOWN)     printf("[DOWN]");
    if (val & JPF_JOY_LEFT)     printf("[LEFT]");
    if (val & JPF_JOY_RIGHT)    printf("[RIGHT]");
}

static void printjoyport(ULONG val)
{
    int i;
    
    for(i = 31; i >= 0; i--)
    {
    	printf("%d", (val & (1 << i)) ? 1 : 0);
    }
    
    printf(" - ");
    
    if ((val & JP_TYPE_MASK) == JP_TYPE_NOTAVAIL) printf("NOT AVAILABLE");
    if ((val & JP_TYPE_MASK) == JP_TYPE_UNKNOWN)  printf("UNKNOWN");
    
    if ((val & JP_TYPE_MASK) == JP_TYPE_JOYSTK)
    {
        printf("JOYSTICK - ");
        printjoydirections(val);
        printbuttons(val);
    }
    
    if ((val & JP_TYPE_MASK) == JP_TYPE_GAMECTLR)
    {
        printf("GAME CONTROLLER - ");
        printjoydirections(val);
        printbuttons(val);
    }

    if ((val & JP_TYPE_MASK) == JP_TYPE_MOUSE)
    {
        printf("MOUSE - ");
        printmousedirections(val);
        printbuttons(val);
    }
    
    if ((val & JP_TYPE_MASK) == JP_TYPE_ANALOGUE)
    {
        printf("JOYSTICK[ANALOGUE] - ");
        printajoydirections(val);
        printbuttons(val);
    }

    printf("\n");
}

int main(int argc, char **argv)
{
    int unit = 1;

    if (argc == 2) unit = atoi(argv[1]);

    LowLevelBase = OpenLibrary("lowlevel.library", 0);

    if (LowLevelBase)
    {
        ULONG old = 0;

        while(!CheckSignal(SIGBREAKF_CTRL_C))
        {
            ULONG new;

            new = ReadJoyPort(unit);
            if (new != old)
            {
	            old = new;
                printjoyport(new);
            }

            Delay(1);
        }
        CloseLibrary(LowLevelBase);
    }

    return 0;
}

Reference

implemented

ULONG ReadJoyPort(ULONG port)
UBYTE GetLanguageSelection()
ULONG GetKey()
VOID QueryKeys(struct KeyQuery * queryArray, UBYTE arraySize)
APTR AddKBInt(const APTR intRoutine, const APTR intData)
VOID RemKBInt(APTR intHandle)
ULONG SystemControlA(const struct TagItem * tagList)
ULONG SystemControl(Tag tagList, ...)
APTR AddTimerInt(const APTR intRoutine, const APTR intData)
VOID RemTimerInt(APTR intHandle)
ULONG ElapsedTime(struct EClockVal * context)
APTR AddVBlankInt(const APTR intRoutine, const APTR intData)
VOID RemVBlankInt(APTR intHandle)
BOOL SetJoyPortAttrsA(ULONG portNumber, const struct TagItem * tagList)


not implemented

BOOL SetJoyPortAttrs(ULONG portNumber, Tag tagList, ...)
VOID StopTimerInt(APTR intHandle)
VOID StartTimerInt(APTR intHandle, ULONG timeInterval, BOOL continuous)

The type of device can be determined by applying the mask JP_TYPE_MASK to the return value and comparing the resultant value with the following: