Post by thread:Push buttons

Hi, As usual, I have some questions today... I am using the check_keys routine from Bob Blick. In fact, it only detects falling edges on portA. I am searching for a routine that could decide between a single press on a switch and a long press on a switch (more than 500ms or 1s). The reason is that I don't have so much I/O on my 16C84 and had like one switch to have more than one function. Can anybody help? -david P.S.: Thanks to everybody for the EEPROM writing, it works nicely since I am waiting for the write to complete :) ;-------- ; test for keypress and call time adjust if needed ;-------- Check_keys movf PORTA,w ;get port "a" xorwf keys,w ;compare with previous andlw b'00000111' ;only care about button pins btfsc STATUS,Z ;zero set=no buttons retlw 0 ;return xorwf keys,f ;store key value movlw 0x64 ;a fairly long delay will movwf scratch ;prevent key bounces Key_delay movlw 0xFF call Delay decfsz scratch goto Key_delay btfss keys,2 ;test "minutes" button goto Inc_mins btfss keys,1 ;test "tens" button goto Inc_tens btfss keys,0 ;test "hours" button goto Inc_hours retlw 0 ;must be a glitch. yeah, right!

David BALDWIN wrote: > > Hi, > > As usual, I have some questions today... I am using the check_keys > routine from Bob Blick. In fact, it only detects falling edges on portA. > I am searching for a routine that could decide between a single press on > a switch and a long press on a switch (more than 500ms or 1s). The > reason is that I don't have so much I/O on my 16C84 and had like one > switch to have more than one function. Can anybody help? > I use a routine in my Timer0 interrupt service that does the following : Is button pressed ? Yes : Increase counter BUTTON_COUNTER Is BUTTON_COUNTER > 10 (This value depends on your app) Yes : Set BUTTON_PRESSED_FLAG No : BUTTON_COUNTER = 0 All you have to do in your main routine, is to look if BUTTON_PRESSED_FLAG is set. If you want to use look for long and short presses, do the following : Use a routine in your Timer0 interrupt service that does the following : Is button pressed ? Yes : Increase counter BUTTON_COUNTER Is BUTTON_COUNTER > 20 (This value depends on your app) Yes : Set LONG_FLAG Is BUTTON_COUNTER > 10 (This value depends on your app) Yes : Set SHORT_FLAG No : BUTTON_COUNTER = 0 Is LONG_FLAG set ? Yes : Set LONG_BUTTON_PRESSED_FLAG Else is SHORT_FLAG set ? Yes : Set SHORT_BUTTON_PRESSED_FLAG All you have to do in your main routine, is to look if SHORT_BUTTON_PRESSED_FLAG, or LONG_BUTTON_PRESSED_FLAG is set. You have to remember to reset the flags after use in your main routine. If you think this is a very long and cumbersome method, here are a few points to consider : 1) Your software never hangs in delay loops 2) The inputs are much better debounced than with just two samples. 3) You work with flags, so you don't have to worry about the debouncing - it happens by itself. 4) If you have multiple inputs, you can optimise the code to be shorter than other methods. 5) If you use this method to debounce keypads, you'll find double keypresses easy. -- Friendly Regards Tjaart van der Walt spam_OUTtjaartTakeThisOuTwasp.co.za _____________________________________________________________ | Another sun-deprived R&D Engineer slaving away in a dungeon | | WASP International http://wasp.co.za | | GSM and GPS value-added applications | | Voice : +27-(0)11-622-8686 | Fax : +27-(0)11-622-8686 | |_____________________________________________________________|

At 07:25 AM 25/03/1997 +0100, you wrote: >I am searching for a routine that could decide between a single press on >a switch and a long press on a switch (more than 500ms or 1s). I'd make one suggestion here. Set up your algo. in such a way that you accept the single press as an action that occurs between the debounce period (50-100ms) and your long press. There is nothing more frustrating to an equipment user than to have the action occur after the button is released. In your example an operator would feel frustrated if they pressed the button down for 400ms and nothing happened but if they pressed for 401ms it did. From an ergonometric prespective users prefer the act of pressing the button to cause an action rather than releasing the button. If the button is used for two totally opposite things you may find this difficult to impliment. Try adding feedback at the moment the debounce period is complete but before you make a choice on button action. An operator, who hears a beep or sees a LED blink, and just wants the short press, will then release the key at which time you could invoke the action. John Pioneers are the ones, face down in the mud, with arrows in their backs. Automation Artisans Inc. Ph. 1-250-544-4950 PO Box 20002 Fax 1-250-544-4954 Sidney, BC CANADA V8L 5C9

David BALDWIN wrote: > As usual, I have some questions today... I am using the check_keys > routine from Bob Blick. In fact, it only detects falling edges on portA. > I am searching for a routine that could decide between a single press on > a switch and a long press on a switch (more than 500ms or 1s). David, Check out my debouncing routine to capture both edges: http://www.interstice.com/~sdattalo/technical/software/pic/debounce.html A simple way to check if a key is pressed for a "long time" is with the following untested code: MOVF previous_state,W ;Get the previous state of the ;switch (i.e. the last time it was ;debounced). XORWF latest_state,W ;Get the latest state of the switch XORWF previous_state,F ;Save latest state as previous state ANDLW BIT_POS_OF_SWITCH ;We're interested in this bit. SKPNZ ;or SKPZ if input is low on key press INCFSZ a_counter,F ;Detected a pressed key count it. CLRF a_counter ;No detection, so clear the counter. If this little chunk of code runs once every 5ms and you want to measure key presses longer than one half of a second, then you simply need to monitor when "a_counter" exceeds 100 (base 10). The state of the switch is the "debounced state". In other words, the debounce routine would first execute before this one. Anyone see the subtlety in the skips? Scott PS. John, CLRF DOES affect the Z-bit on 16Cxx parts too. You will have to make many, many, many more mistakes before any embarassment is warranted though.