Guru
Joined: 07/08/2011
Location: AustraliaPosts: 6546
| Posted: 10:55pm 15 Nov 2012 |
My new toy arrived today.
The UBW32 is on the left. I really must get one of Mick's boards for the final installation!
The display works well with the Maximite and I have a rough working touch program.
Only two extra resistors were needed for a low parts count.
I have to do a bit more fine tuning with the timing delays but I am pleased with a first attempt.
See the XPT2046 or ADS7843 data sheets for a good description of how the resistive touch screen works.
How the interrupt works:
TouchIntEnable is set high
Y2 is set low
When the touch contact is made the low resistances of the X and Y resistors pulls TouchInt low.
This triggers the interrupt.
TouchIntEnable is then turned off to prevent it from interfering with the readings.
X1 is driven High and X2 low and the mid point voltage read through Y1. The Y resistance has no effect on the reading due to the high input impedence.
Y1 is then driven high and Y2 low and the Y positoin is read through X1.
The delays are needed because of the high capacitance of the touchscreen and we need settling time.
***EDIT: In my real circuit, I have the Interrupt connected to the Y resistor and grounded X2. The theory is the same and it doesn't matter which way it's done.
' touch display demo
' by TassyJim
' 16 Nov 2012
' see the XPT2046 or ADS7843 data sheets for a description
' of how the resistive touch screen works
cls
TouchY1=37 ' 4 analogue input pins for the resistors
TouchY2=35
TouchX1=38
TouchX2=36
TouchIntEnable=34 ' any digital output pin
TouchInt=28 ' digital interupt pin
gosub _touchEnable
_mainLoop:
'do stuff while waiting for a touch
if t=1 then
font 1, 4
print @(100, 40)"X ";Xhit;" ";@(100, 90)"Y ";Yhit;" "
pause 100
gosub _touchEnable
endif
goto _mainLoop
_touchEnable:
setpin TouchY1, 1
setpin TouchY2, 1
setpin TouchX1, 1
setpin TouchX2, 8
Pin(TouchX2)=0
setpin TouchIntEnable, 8
pin(TouchIntEnable)=1
pause 100
setpin TouchInt, 7, _Touched
t=0
return
_Touched:
pause 5 ' debounce time
if pin(TouchInt)=0 then ' touch still there
setpin TouchInt, 0 ' disable the interupt
setpin TouchIntEnable,0 ' disable the interupt resistor
setpin TouchX1, 8 '
Pin(TouchX1)=1 ' X1 is now high and X2 low
pause 5
Xvolt=pin(TouchY1) ' read the X position using Y1
setpin TouchX1, 1
setpin TouchX2, 1 ' set the X as input
setpin TouchY1, 8 ' and the Y as potential divider
setpin TouchY2, 8
Pin(TouchY1)=1
Pin(TouchY2)=0
pause 5
Yvolt=pin(TouchX1) ' read the Y position using X1
Xhit=int(mm.hres*Xvolt/3.3) ' you can scale to any value here
Yhit=int(mm.vres*Yvolt/3.3)
if Xhit >470 or Yhit < 5 then 'reading is suspect
Xhit=0 ' so set the results to zero
Yhit=0
endif
t=1 ' flag to indicate a touch decoded
endif
ireturn
' by TassyJim
' 16 Nov 2012
' see the XPT2046 or ADS7843 data sheets for a description
' of how the resistive touch screen works
cls
TouchY1=37 ' 4 analogue input pins for the resistors
TouchY2=35
TouchX1=38
TouchX2=36
TouchIntEnable=34 ' any digital output pin
TouchInt=28 ' digital interupt pin
gosub _touchEnable
_mainLoop:
'do stuff while waiting for a touch
if t=1 then
font 1, 4
print @(100, 40)"X ";Xhit;" ";@(100, 90)"Y ";Yhit;" "
pause 100
gosub _touchEnable
endif
goto _mainLoop
_touchEnable:
setpin TouchY1, 1
setpin TouchY2, 1
setpin TouchX1, 1
setpin TouchX2, 8
Pin(TouchX2)=0
setpin TouchIntEnable, 8
pin(TouchIntEnable)=1
pause 100
setpin TouchInt, 7, _Touched
t=0
return
_Touched:
pause 5 ' debounce time
if pin(TouchInt)=0 then ' touch still there
setpin TouchInt, 0 ' disable the interupt
setpin TouchIntEnable,0 ' disable the interupt resistor
setpin TouchX1, 8 '
Pin(TouchX1)=1 ' X1 is now high and X2 low
pause 5
Xvolt=pin(TouchY1) ' read the X position using Y1
setpin TouchX1, 1
setpin TouchX2, 1 ' set the X as input
setpin TouchY1, 8 ' and the Y as potential divider
setpin TouchY2, 8
Pin(TouchY1)=1
Pin(TouchY2)=0
pause 5
Yvolt=pin(TouchX1) ' read the Y position using X1
Xhit=int(mm.hres*Xvolt/3.3) ' you can scale to any value here
Yhit=int(mm.vres*Yvolt/3.3)
if Xhit >470 or Yhit < 5 then 'reading is suspect
Xhit=0 ' so set the results to zero
Yhit=0
endif
t=1 ' flag to indicate a touch decoded
endif
ireturn
The next job is to get some working menus
(and work out where in the caravan it is going to live)
Jim
VK7JH
MMedit