ADB Count
Volume Number: 6
Issue Number: 5
Column Tag: XCMD Corner
Related Info: ADB Manager
CountADBs and Reality 
By Donald Koscheka, , Mark Armstrong
Note: Source code files accompanying article are located on MacTech CD-ROM orsource code disks.
This column strives to present interesting insights into enhancing Hypercard
through XCMDs. When I started writing this column almost two years ago, I was
apprehensive; how would I come up with a new idea each month year in and year out.
The answer to this question was something of a revelation to me -- once I decided to
keep coming up with new ideas, I began looking in new places for those ideas. No part
of Macintosh programming is off-limits, I explore everything. Of course there are
limits to what one person can do and I find myself very often writing a column in
response to some question asked by a colleague or a reader.
I’ve decided that it’s time to go one step further. Beginning this month,
intermittently offer this space for “guest XCMDs” such as Mark Armstrong’s
following ADB externals. The guest columnist idea appeals to me for two reasons: (1)
it broadens the column’s “reach” by discussing areas that I may have not explored
myself and (2) it provides you with different perspectives and coding styles so that
you can see how others have solved specific problems in an XCMD. This is an open
invitation. If you would like to have your XCMD published, send it to me via AppleLink
(N0735) or America OnLine (AFC Donald) or to the Editor. Use Macwrite or TEXT
only. I will respond as quickly as possible to inform you as to whether I can use the
article or not. A few rules: If I can use the material, I will edit it and return it to you
for approval. I edit for style and grammar, expect to have some work done to your
prose. Don’t submit anything that you don’t want in the public domain and don’t
submit any article without source code. You may use whatever language you like. Give
yourself a “short plug” at the beginning of the column so that other readers get to
know you better.
This month, I would like to introduce Mark Armstrong, Vice President of
Research and Development at Pharos Technologies, Inc, a software development and
systems integration company in Cincinnati, Ohio. Mark has written one commercial
engineering application on the Macintosh called “UNITize” and has contributed to the
arcade-style game “Marble Madness”. With his physics degree firmly in hand, he
still wonders how he got mixed up in all this.
CountADBs and Reality
In some circumstances (such as on the factory floor), there is a need to monitor
the Macintosh to determine whether the mouse or keyboard devices become detached
from ADB. Some software may modify their behavior if certain input devices are
available, hiding or showing functionality based on that result. Below are two simple
XFCN’s, developed in Think C 4.0, that tell you if the mouse and keyboard are
connected.
According to Inside Macintosh Volume 5, the function CountADBs() “returns a
value representing the number of devices connected to the Apple Desktop Bus (ADB) by
counting the number of entries in the device table....” The important word is
representing. It does not really tell you what is connected out there on the bus.
Consequently, even if you have no devices hooked up to ADB, CountADBs() will return a
value of 2. This happens because the system always installs the keyboard and mouse
drivers regardless of whether they are physically resident. To find out what is really
connected to ADB you can poll devices that you believe are connected to the ADB.
Connected devices will respond to the poll.
Before going too far, you must determine whether the host machine is equipped
for ADB. The following call to SysEnvirons() determines whether ADB is installed.
/* 1 */
Boolean ADBExists()
{
SysEnvRec theWorld;
OSErr err;
err = SysEnvirons(1,&theWorld);
if (err) return (FALSE);
else
{
if ((theWorld.machineType >= 0) && (theWorld.machineType < 3))
return (FALSE);
else return (TRUE);
}
}
Once you have determined that ADB exists on your machine, you check to see
what devices are actually there by looping from 1 to the maximum allowable number
of ADB devices (16). Inside the loop, you call ADBIndAvail() which returns TRUE if
the specified device is physically connected and functional or FALSE otherwise.
ADBIndAvail() takes a device specified by the index and sends a command via ADBOp()
to that device to see if it is responding. If the device receives the operation, it will
signal that it has done so by executing a completion routine. If the completion routine
ADBOp() doesn’t execute, then the device did not receive the message, and we can
assume that the device is dysfunctional or disconnected. The completion routine
ADBComplete() sets a global variable to TRUE. If completion does not occur, then the
operation times out and the global variable remains FALSE. In the following code, we
use the first byte of Scratch8 as the global variable. We chose to use Scratch8 because
this code was developed for a Think C 4.0 XCMD where A4 had already been pushed
using SetUpA4(). In most cases, a regular global variable will do the trick.
/* 2 */
#define ADB_TIMEOUT 10000
extern char Scratch8[] : 0x9FA;
ADBComplete(){
*(char *)Scratch8 = TRUE;
}
ADBIndAvail(index)
short index;
{
ADBAddress addrs;
ADBDataBlock devBlock;
OSErr err;
short cmdNum;
Str255 ADBData;
addrs = GetIndADB(&devBlock,index);
cmdNum = ((addrs*16)+0xF);
ADBData[0] = 0;
ADBData[1] = 0;
ADBData[2] = 0;
*(char *)Scratch8 = FALSE;
err = ADBOp(NIL,ADBComplete,&ADBData,cmdNum);
if (!err){
short I= 0;
do
if (++I > ADB_TIMEOUT) *(char *)Scratch8 = TRUE;
while (!*(char *)Scratch8);
if (ADBData[0] != 0) return (TRUE);
}
return (FALSE);
}
In both cases below, the first portion of the code checks to see if the first and only
argument is a question mark (?) or an exclamation point (!). If so, the XFCN
responds appropriately as suggested by MacDTS.
The XFCN checks first to see if ADB exists on this machine and returns an error
code if it does not. Next, it loops through all the devices to see if any one of them is a
responding mouse. If it finds one, it returns TRUE, otherwise it completes the loop and
returns FALSE. Each time through the loop, we call GetIndADB(), as directed in Inside
Mac, to determine if the device in question is, indeed, a mouse.
/* 3 */
#include “MacTypes.h”
#include “HyperXCmd.h”
#include “DeskBus.h”
#include “SetUpA4.h”
#define ADB_KEYBOARD 2
#define ADB_MOUSE 3
#define STANDARD_KBD 1
#define EXTENDED_KBD 2
#define MAX_ADB_DEVICES 16
pascal main(paramPtr)
XCmdBlockPtr paramPtr;
{
Str255 str;
short ix;
RememberA0();
SetUpA4();
if(paramPtr->paramCount == 1){
ZeroToPas(paramPtr,*((unsigned char **)paramPtr->params[0]),str);
if (str[0] == 1){
if (str[1] == ‘?’)
pstrcpy(str,”\pKBDAvail()”);
else if (str[1] == ‘!’)
pstrcpy(str,”\pv1.0; © Pharos Technologies, Inc. 1989");
}
goto Done;
}
if (!ADBExists()){
pstrcpy(str,”\p0\rnoADB”);
goto Done;
}
for ( ix =1; ix <=MAX_ADB_DEVICES; ix ++){
ADBDataBlock ADBinfo;
ADBAddress ADBaddr;
if (!ADBIndAvail( ix )) continue;
ADBaddr = GetIndADB(&ADBinfo,I);
if (ADBaddr <= 0) continue;
if (ADBinfo.origADBAddr == ADB_MOUSE){
pstrcpy(str,”\ptrue”);
goto Done;
}
}
pstrcpy(str,”\pfalse”);
Done:
paramPtr->returnValue = PasToZero(paramPtr,(StringPtr)str);
RestoreA4();
}
A similar routine checks for keyboard devices. This routine not only checks to
see if it is a keyboard, but also returns the type of keyboard by examining the devType
field of ADBInfo.
/* 4 */
#include “MacTypes.h”
#include “HyperXCmd.h”
#include “DeskBus.h”
#include “SetUpA4.h”
#define ADB_KEYBOARD 2
#define ADB_MOUSE 3
#define STANDARD_KBD 1
#define EXTENDED_KBD 2
#define MAX_ADB_DEVICES 16
pascal main(paramPtr)
XCmdBlockPtr paramPtr;
{
Str255 str;
short I;
RememberA0();
SetUpA4();
if (paramPtr->paramCount == 1){
ZeroToPas(paramPtr,*((unsigned char **)paramPtr->params[0]),str);
if (str[0] == 1){
if (str[1] == ‘?’)
pstrcpy(str,”\pKBDAvail()”);
else if (str[1] == ‘!’)
pstrcpy(str,”\pv1.0; © Pharos Technologies, Inc. 1989");
}
goto Done;
}
if (!ADBExists()){
pstrcpy(str,”\p0\rnoADB”);
goto Done;
}
for (I=1;I<=MAX_ADB_DEVICES;I++){
ADBDataBlock ADBinfo;
ADBAddress ADBaddr;
if (!ADBIndAvail(I)) continue;
ADBaddr = GetIndADB(&ADBinfo,I);
if (ADBaddr <= 0) continue;
if (ADBinfo.origADBAddr == ADB_KEYBOARD){
if (ADBinfo.devType == STANDARD_KBD){
pstrcpy(str,”\ptrue,standard”);
goto Done;
}
else if (ADBinfo.devType == EXTENDED_KBD){
pstrcpy(str,”\ptrue,extended”);
goto Done;
}
else{
pstrcpy(str,”\ptrue,unknown”);
goto Done;
}
}
}
pstrcpy(str,”\pfalse”);
Done:
paramPtr->returnValue = PasToZero(paramPtr,(StringPtr)str);
RestoreA4();
}
Once you know how to identify a particular device, it is easy to check to see if it
is present on ADB. If you don’t know how to identify a given device, then the code above
can be easily modified to return all devices found on ADB. By the way, I would like to
give special thanks and credit to Cameron Birse. If you don’t recognize the name from
any number of “sources”, then never mind.
Referenced by (2):