Post by thread:What is the best way to sense a pushbutton press??

Hello, What is the best way to sense a push button press? I am multiplexing the PORTB data lines as a data bus and using PORTA as chip select as shown to me by Steve Smith. Will the below circuit work? An HC74 D Flip-Flop is used to capture a push button press since inputs will only be scanned briefly and I don't want to miss the press. The inputs are selected by selecting RD1 and storing to a register. If PB0 reads as set then I know that the button was pressed. I then reset the F/F by selecting WR1 and tickling PB7. Is there a better way to achieve this??? I need to multiplex the pins since there are many inputs and outputs (LCD display, ISD voice chip etc) All comments are appreciated (but go easy on me -- I am also a newbie!) Thanks in advance! -Randie Ohtsji spam_OUTrohtsjiTakeThisOuTglenayre.com PS I hope my crude schematic shows what I am doing. Vcc +--------------To PIC16F84 | | PORTB0-7 / | \ | / | \ | / | N.O. Push button | | _|_ | __________ | | | | +-----0 0-------Gnd | 8 | Q0|---- | +----/---------| HC373 Q1|---- | | | __ Q2|---- ____0___ | GND-----0 OE Q3|---- | _ | | | Q4|---- +----|D S Q|------------+ | | Q5|---- | | HC74 | | | | Q6|---- | | _| | | WR1----|LAT Q7|-------------->CLK _ Q|-----+ | | |__________| | |____R___| | | | | 0 | | | | | | | | +-------------------+ | | | | | __________ \ | | | | / | | | A0|------------------ \ ---------------+ | 8 | HC244 A1| / +-----/--------| A2| \ | ___ A3| / RD1--+----0 OE1 A4| | | | ___ A5| Vcc +----0 OE2 A6| | A7| |__________| __________ | __ | WR1-----0 Y0 A0|------- \ | __HC138 | \ RD1-----0 Y1 A1|------- \ To PIC16F84 | __ | / PORTA0-2 0 Y2 A2|------- / | __ | 0 Y3 CS1|-----/\/\/\----Vcc | __ ___| 0 Y4 CS20---+------GND | __ ___| | 0 Y5 CS30---+ | __ | 0 Y6 | | __ | 0 Y7 | |__________|

-----Original Message----- From: Randie Ohtsji [4555] <.....rohtsjiKILLspam@spam@GLENVAN.GLENAYRE.COM> To: PICLISTKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Date: Thursday, 16 October 1997 14:42 Subject: What is the best way to sense a pushbutton press??? {Quote hidden}>Hello, > >What is the best way to sense a push button press? I am multiplexing the >PORTB data lines as a data bus and using PORTA as chip select as shown >to me by Steve Smith. Will the below circuit work? > >An HC74 D Flip-Flop is used to capture a push button press since inputs >will only be scanned briefly and I don't want to miss the press. > >The inputs are selected by selecting RD1 and storing to a register. >If PB0 reads as set then I know that the button was pressed. I then >reset the F/F by selecting WR1 and tickling PB7. > >Is there a better way to achieve this??? I need to multiplex the pins >since there are many inputs and outputs (LCD display, ISD voice chip etc) Use the B lines(1) in interrupt mode, with the soft pullups (downs?) enabled. If you've got an array of switches to multiplex, try and arrange them in a regular shape. the other side of the switch goes to some more pins(2), that are set to the opposite sense. When any button is pushed, it will trigger an interrupt. In the ISR, you clear lines(2), and then set one at a time, reading the lines(1) to find out which switch caused it. Some debounce is necessary. Sorry about the awkward description - haven't a data source nearby!!

Mike, Thanks for the response! The B lines (PB0 - PB7) are used as both inputs and outputs (with HC373 and HC244 chips) so I can't dedicate them to trigger an interrupt from a switch. There will be about 4x HC373 and 2x HC244 used (chip selected by the HC138) so the B lines sequence will go something like: Output1, Output2, Input1, Output3, Output4, Input2. The switch will be on Input2. ......err I hope you are getting what I am trying to say. Since the B lines will only look at Input2 (the switch input) a minimum of 1/6 of the time, I need to capture the switch press by using the Flip-flop. Is the circuit and logic of what I am attempting to do the best way to capture a switch press???? I thought the Flip-Flop could be used for de-bounce. Thanks! -Randie /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ */ Randie Ohtsji /* /* Glenayre R&D, Vancouver, BC CANADA Phone: (604) 293-1611 x4555 */ */ Email: EraseMErohtsjispam_OUTTakeThisOuTglenayre.com Fax: (604) 293-4317 /* /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ {Quote hidden}> From msmithspam_OUTPASTEUR.DIALIX.COM.AU Thu Oct 16 05:31:09 1997 > MIME-Version: 1.0 > Content-Transfer-Encoding: 7bit > X-Priority: 3 > X-MSMail-Priority: Normal > X-MimeOLE: Produced By Microsoft MimeOLE V4.71.1712.3 > Date: Thu, 16 Oct 1997 21:16:46 +0930 > From: Mike Smith <@spam@msmithKILLspamPASTEUR.DIALIX.COM.AU> > Subject: Re: What is the best way to sense a pushbutton press??? > To: KILLspamPICLISTKILLspamMITVMA.MIT.EDU > > {Original Message removed}

On Thu, 16 Oct 1997 09:29:33 -0700 "Randie Ohtsji [4555]" <spamBeGonerohtsjispamBeGoneGLENVAN.GLENAYRE.COM> writes: >The B lines (PB0 - PB7) are used as both inputs and outputs (with >HC373 >and HC244 chips) so I can't dedicate them to trigger an interrupt from >a switch. There will be about 4x HC373 and 2x HC244 used (chip >selected >by the HC138) so the B lines sequence will go something like: Output1, >Output2, Input1, Output3, Output4, Input2. The switch will be on >Input2. Do all the outputs first, then all the inputs, so it doesn't need to adjust the TRIS register every time. Set up an 8-byte block of RAM to keep the last output values and the most recent input values. Unless the project requres very fast responses to something, do all the I/O at once periodically. The program examines and changes the RAM. This will keep from scattering I/O routines all over the program should you decide to use a different I/O arrangement later. >......err I hope you are getting what I am trying to say. > >Since the B lines will only look at Input2 (the switch input) a >minimum >of 1/6 of the time, I need to capture the switch press by using the >Flip-flop. > No you don't. You just need to go in the input2 mode and read the switches at least as often as the shortest time the user is likely to hold the switch down. This is about 40 ms. Store the switch reading in RAM. The program can then look at it any time. Usually it is useful to detect when a switch was open but is now closed (when it is first pressed). This can be done by ANDing the new value with the complement of the old value. The somewhat cryptic code below does this with 2 RAM locations. Location switches must be preserved between uses of the routine, location dswitches doesn't need to be. [Set hardware so PORTB is routed to switches] comf PORTB,w ;Get new switch settings (bit=1 if pressed). xorwf switches,w ;Form difference with old value. xorwf switches,f ;Update old value to be new. ; Now we have switches = new reading, and W = change from old ; to new reading. If a switch has changed since it was last read, ; the bit in dswitches will be 1. But the only change we care about ; is pressing the switch, not releasing it. So adjust W to ; clear the bits for any switches that are now released. andwf switches,w ;And with present reading 1=pressed. movwf dswitches ;Fix so only newly pressed are ones. The program can now examine switches and dswitches and make decisions accordingly. The routine should be executed only evey 20 ms or so to prevent bounce problems. >Is the circuit and logic of what I am attempting to do the best way to >capture a switch press???? All you need for circuitry is a switch to ground, resistor to Vcc, connect that to the input of the 244, output of 244 to PIC. > >I thought the Flip-Flop could be used for de-bounce. You don't need any explicit debounce if you don't read the switch too often. About every 20 ms works out well. Most switches will not bounce for longer than 10ms or so.

Hi Mike, Sorry about the CC (are you getting two of this message, if so please let me know and I will stop CCing you). Yes, I am using an old version of OrCAD (v4.???). I'm very new to the PIC, but I have a 16C84-04 and a 16F84-10 to play with. This PIC list is great -- I found out a lot from all the email bouncing around (but I still have a LOT to learn). I would appreciate any hints, circuits, starting points, etc. I want to connect a 2x16 line LCD (8 data lines + 3 control lines), a fully addressed ISD voice chip (10 address lines + 3 control lines + 2 status lines), compass module (1 data line + 4 control lines), serial communication (PIC to PIC: 1 data line + gnd). 3 or 4 push buttons, Hex rotary switch - BCD format (4 lines) and 2 or 3 misc I/O (2 or 3 lines?). Also maybe some motor control lines and a data line for hall effect sensor (to keep track of motor). If there is enough I/O, then maybe control the LCD contrast with digital pot (4 lines?). Digital volume control would be nice too (4 control lines - using a digital pot???). Does the PIC need to read data FROM the LCD. I know that bit 7 needs to be read for the LCD busy flag, but do the rest of the lines need to be accessed??? I wish to do a few custom graphic characters in the LCD (an Up and Down arrow.....funny that they don't have these, as there is a left and right arrow in the character set). I think that I am allowed to create up to 8 custom characters???? More questions: A) I wish to use: 1) The internal watchdog 2) The timer for PIC to PIC serial communication 3) The timer for frequency measurement (20KHz to 80KHz) Can I do this? I was thinking that if I can't, then maybe using an external watchdog & power sense chip (Dallas DS1232). B) How can I isolate the lines to implement in-circuit-programming (ICP)? I wish to use have access to the MCRL line for reset from external watchdog & power sense chip and also a pushbutton manual reset. How can I isolate the B lines (PB6 & PB7 used for programming)? I was think of using an HC245 and disabling the chip (Z state) when using ICP but then I would need to enable the chip when using it for the real circuit. I can use a PNP transistor to isolate the PIC and HC245 chip power so that they are the only ones powered up during ICP. Comments???? .....please! Thanks -Randie /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ */ Randie Ohtsji /* /* Glenayre R&D, Vancouver, BC CANADA Phone: (604) 293-1611 x4555 */ */ Email: TakeThisOuTrohtsjiEraseMEspam_OUTglenayre.com Fax: (604) 293-4317 /* /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ {Quote hidden}> From RemoveMEmsmithTakeThisOuTpasteur.dialix.com.au Fri Oct 17 05:12:25 1997 > From: "Mike Smith" <msmithEraseME.....pasteur.dialix.com.au> > To: "Randie Ohtsji [4555]" <EraseMErohtsjiglenvan.glenayre.com> > Subject: Re: What is the best way to sense a pushbutton press??? > Date: Fri, 17 Oct 1997 21:36:10 +0930 > MIME-Version: 1.0 > Content-Transfer-Encoding: 7bit > X-Priority: 3 > X-MSMail-Priority: Normal > X-MimeOLE: Produced By Microsoft MimeOLE V4.71.1712.3 > > > {Original Message removed}

Randie Ohtsji [4555] wrote: > Hi Mike, > > Sorry about the CC (are you getting two of this message, if so please > let me know and I will stop CCing you). > Exactly what does CC do? I haven't used it, but would like to know what it does. > Yes, I am using an old version of OrCAD (v4.???). Ah Another one.... {Quote hidden}> I'm very new to > the PIC, but I have a 16C84-04 and a 16F84-10 to play with. This > PIC list is great -- I found out a lot from all the email bouncing > around (but I still have a LOT to learn). I would appreciate > any hints, circuits, starting points, etc. > > I want to connect a 2x16 line LCD (8 data lines + 3 control lines), > a fully addressed ISD voice chip (10 address lines + 3 control > lines + 2 status lines), compass module (1 data line + 4 control > lines), serial communication (PIC to PIC: 1 data line + gnd). > 3 or 4 push buttons, Hex rotary switch - BCD format (4 lines) > and 2 or 3 misc I/O (2 or 3 lines?). Also maybe some motor control > lines and a data line for hall effect sensor (to keep track of motor). > If there is enough I/O, then maybe control the LCD contrast with > digital pot (4 lines?). Digital volume control would be nice too > (4 control lines - using a digital pot???). > That's a load of stuff! You'll be busy a while with port-expansion! > Does the PIC need to read data FROM the LCD. I know that bit 7 needs > to be read for the LCD busy flag, but do the rest of the lines need > to be accessed??? I wish to do a few custom graphic characters in the > LCD (an Up and Down arrow.....funny that they don't have these, as > there is a left and right arrow in the character set). I think that I > am allowed to create up to 8 custom characters???? > I don't think you need to read the LCD. You can save one i/o that way (R/W).You don't need to read the busy flag - you can use delays. Slower though (not much). You can save 4 I/O lines by simply using the LCD in nibble mode (slower again) > More questions: > snip > B) How can I isolate the lines to implement in-circuit-programming (ICP)? > I wish to use have access to the MCRL line for reset from external > watchdog & power sense chip and also a pushbutton manual reset. > How can I isolate the B lines (PB6 & PB7 used for programming)? > How serious are you about this? Can you use a jumper for running/programming? Or will your unit be totally enclosed? {Quote hidden}> I was think of using an HC245 and disabling the chip (Z state) when > using ICP but then I would need to enable the chip when using it for > the real circuit. > > I can use a PNP transistor to isolate the PIC and HC245 chip power > so that they are the only ones powered up during ICP. > > Comments???? .....please! > > Thanks > > -Randie > > /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ > */ Randie Ohtsji /* > /* Glenayre R&D, Vancouver, BC CANADA Phone: (604) 293-1611 x4555 */ > */ Email: RemoveMErohtsjiEraseMEEraseMEglenayre.com Fax: (604) 293-4317 /* > /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ > > > From RemoveMEmsmithspam_OUTKILLspampasteur.dialix.com.au Fri Oct 17 05:12:25 1997 > > From: "Mike Smith" <RemoveMEmsmithTakeThisOuTspampasteur.dialix.com.au> > > To: "Randie Ohtsji [4555]" <EraseMErohtsjispamspamBeGoneglenvan.glenayre.com> > > Subject: Re: What is the best way to sense a pushbutton press??? > > Date: Fri, 17 Oct 1997 21:36:10 +0930 > > MIME-Version: 1.0 > > Content-Transfer-Encoding: 7bit > > X-Priority: 3 > > X-MSMail-Priority: Normal > > X-MimeOLE: Produced By Microsoft MimeOLE V4.71.1712.3 > > > > > > {Original Message removed}

Hullo Mike! > Wow!! Can I suggest a rethink. Look at an I2C (pronounced eye- > squared-see) data book. The I2C is a 2wire protocol that supports I'm a little confused about I2C. Is this an actual IC chip that I need to connect to the PIC? Or do I use this instead of the PIC? Can you recommend any web-sites or manufacturers of this (if it is a chip) please. > on writes. What sort of motor control? stepper/servo? can do in i2c. Not quite sure if I'm going to use a stepper motor or a regular motor with a hall effect sensor. I want to spin a plate around and send out burst of data (PIC to PIC communication) 45 or 90 degree increments (ie send out a burst at: 0 degrees, 90 degrees, 180 degrees, 270 degress) I was think of using the hall effect sensor to sync up when I reach 0 degrees (cheaper than a stepper motor....I think). > Urr, are you using an integrated chip/display? These offer differing > address modes serial/nibble/byte sometimes. Only other reason to read > would be to do a dump of the contents of the display, or the char gen - with > a view to doing read/modify/write to either one. I would be using a standard integrated chip/display (Sharp or Seiko or Optrex 2 x 16 LCD display) > clear wdt. eg latter case - if you have noise prone design micro can latch > up so a s/w reset won't fix - or brownouts will stop it working too. If its > a life or death thing (and it better not be - it can't checksum itself) then > an external wdt is the way to go. The DS1232 is a micromonitor chip which will provide 3 functions: 1) Power monitor for brown outs. 2) Watchdog 3) Push button reset Any of the 3 conditions will produce a 250mS reset pulse. I wish to do all three. >> 2) The timer for PIC to PIC serial >> communication > > Async (RS232) or sync? The latter is probably easier and faster. If you > dont need speed, you could put both on i2c bus - it is multi-master. (but, I will be doing sync communication. I just want to use 2 lines (data & gnd) as I may want to do this over an RF link in the future. I not using RS232. Speed is not really a concern. I bought "Easy Pic'n" and "Pic'n up the Pace" and PIC to PIC communication is implemented by using the timer. I thought perhaps I could use this. But of course I am open to better or alternate ways of achieving this. I guess my main question was can I do all three items as they all use the timer in some way. > You're using a connector to connect to your ICP, right? How about making it > something like a 10 way dil ribbon connector. When not in program mode use > links to route thru to your regular cct. Its a lo tech soln, but sometimes > they are ok. Depends on skill of assemblers. I guess I'm going overboard. I was thinking of the circuit automatically switching to ICP mode once the connector was plugged in and switching back to normal mode with the connector removed. I'm using an 8 position RJ45 connector as the ICP port. I have since given up the automatic mode and installed 2-position jumpers to isolate the circuit. > What IS it? If I tell you....... I will have to kill you! ;) Just kidding, it is actually a remote data logger/transmitter. > If i2c is not for you, let me know, and I'll see where the mux techniques > lead. Still thinking about mux as I don't know too much about I2C. Can you send info please. Thanks in advance! -Randie /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ */ Randie Ohtsji /* /* Glenayre R&D, Vancouver, BC CANADA Phone: (604) 293-1611 x4555 */ */ Email: RemoveMErohtsjiKILLspamglenayre.com Fax: (604) 293-4317 /* */ ________ /* /* / ____/ /__ ____ ____ ___ _________ */ */ / /___/ / _ \/ __ \/ __ `/ / / / __/ _ \ /* /* / /_\ / / __/ / / / /_/ / /_/ / / / __/ */ */ \____/_/\___/_/ /_/\__,_/\__ /_/ \___/ /* /* ________________________/ / */ */ /_________________________/ /* /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/

Can anyone direct me to where I can get a copy of the I2C protocol definition. Is I2C better than SPI?? What are the differences between the two? Does anyone have any examples of I2C or SPI code using a 16F84? Thanks! -Randie ....so many questions, one little brain.......where am I going to find room to stuff in the answers?? /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ */ Randie Ohtsji /* /* Glenayre R&D, Vancouver, BC CANADA Phone: (604) 293-1611 x4555 */ */ Email: rohtsjiSTOPspamspam_OUTglenayre.com Fax: (604) 293-4317 /* */ ________ /* /* / ____/ /__ ____ ____ ___ _________ */ */ / /___/ / _ \/ __ \/ __ `/ / / / __/ _ \ /* /* / /_\ / / __/ / / / /_/ / /_/ / / / __/ */ */ \____/_/\___/_/ /_/\__,_/\__ /_/ \___/ /* /* ________________________/ / */ */ /_________________________/ /* /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ P.S. [OT] I just met with our Microchip rep and he was saying other Flash parts are due in 2Q98 - 3Q98. He's never heard of Scenix. > > I'm a little confused about I2C. Is this an actual IC chip that I > > need to connect to the PIC? Or do I use this instead of the PIC? > > Can you recommend any web-sites or manufacturers of this (if it is > > a chip) please. > > > I2C is a protocol that can be implemented in software, the reason > it is popular is because it is two wire, multimaster, can address alot of > devices and because there are quite a few devices out there that conform > to the standard. TTYL >

Bob Lunn 10/21/97 10:08 AM > Can anyone direct me to where I can get a copy of the > I2C protocol definition. Look at a datasheet for any pic that supports SPI/IIC comms, such as the 16C74. These provide quite good descriptions of the protocols. Alternatively, look at the datasheets for any serial eeprom that uses either of these protocols (eg: 24C01 for IIC or 25LC040 for SPI). All of these datasheets are available from the Microchip web site. > Is I2C better than SPI?? As usual, it depends. 'Standard' IIC only provides data transfer rates up to 100kHz, though 'fast' IIC goes to 400kHz. In contrast, standard SPI goes to 2MHz. The choice is usually based on the hardware that you want to use. If your hardware requires SPI then you use that; if it requires IIC ditto. In the absence of a hardware constraint I always choose IIC. > What are the differences between the two? SPI is owned by Motorola. IIC is owned by Philips. :) > Does anyone have any examples of I2C or SPI code using > a 16F84? I believe there are appnotes showing bit-banged IIC on the Microchip web site, but I don't know the number. ___Bob

Get: http://www-us.semiconductors.philips.com/acrobat/3114.pdf "The I2C-Bus and How to Use It (including specifications). Also, search on their www page for other references. http://www-us.semiconductors.philips.com/search/ For code, goto http://www.microchip.com and look for AN578 and AN554. Rick Watson The University of Texas, ACITS Networking Services, 512/475-9220 spamBeGoner.watsonSTOPspamEraseMEutexas.edu Randie Ohtsji [4555] wrote: {Quote hidden}> > Can anyone direct me to where I can get a copy of the I2C protocol > definition. Is I2C better than SPI?? What are the differences > between the two? Does anyone have any examples of I2C or SPI code > using a 16F84? > > Thanks! > > -Randie > ....so many questions, one little brain.......where am I going to > find room to stuff in the answers?? > > /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ > */ Randie Ohtsji /* > /* Glenayre R&D, Vancouver, BC CANADA Phone: (604) 293-1611 x4555 */ > */ Email: KILLspamrohtsjispamBeGoneglenayre.com Fax: (604) 293-4317 /* > */ ________ /* > /* / ____/ /__ ____ ____ ___ _________ */ > */ / /___/ / _ \/ __ \/ __ `/ / / / __/ _ \ /* > /* / /_\ / / __/ / / / /_/ / /_/ / / / __/ */ > */ \____/_/\___/_/ /_/\__,_/\__ /_/ \___/ /* > /* ________________________/ / */ > */ /_________________________/ /* > /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/ > > > P.S. [OT] I just met with our Microchip rep and he was saying other Flash > parts are due in 2Q98 - 3Q98. He's never heard of Scenix. > > > > > > I'm a little confused about I2C. Is this an actual IC chip that I > > > need to connect to the PIC? Or do I use this instead of the PIC? > > > Can you recommend any web-sites or manufacturers of this (if it is > > > a chip) please. > > > > > I2C is a protocol that can be implemented in software, the reason > > it is popular is because it is two wire, multimaster, can address alot of > > devices and because there are quite a few devices out there that conform > > to the standard. TTYL > > >

-----Original Message----- From: Randie Ohtsji [4555] <TakeThisOuTrohtsji.....TakeThisOuTGLENVAN.GLENAYRE.COM> To: TakeThisOuTPICLISTKILLspamspamMITVMA.MIT.EDU <.....PICLISTRemoveMEMITVMA.MIT.EDU> Date: Tuesday, 21 October 1997 2:13 Subject: Re: What is the best way to sense a pushbutton press??? {Quote hidden}>Hullo Mike! > >> Wow!! Can I suggest a rethink. Look at an I2C (pronounced eye- >> squared-see) data book. The I2C is a 2wire protocol that supports > >I'm a little confused about I2C. Is this an actual IC chip that I >need to connect to the PIC? Or do I use this instead of the PIC? >Can you recommend any web-sites or manufacturers of this (if it is >a chip) please. > No, I2C is a serial communication standard that allows low-medium speed communications to occur over 2 wires, Phillips invented it, and there are a lot of peripheral chips out there that utilise this protocol. You don't need a special chip to generate it at the PIC end, you just twiddle two lines. (actually, you set the port bits you are going to use low, and twiddle the data direction bits if you do it properly - the lines have 2 pullup resistors) The PIC apps manual explains it somewhat, although I've seen better. Maybe the Phillips site? Anyone else know?? > >> on writes. What sort of motor control? stepper/servo? can do in i2c. > >Not quite sure if I'm going to use a stepper motor or a regular motor >with a hall effect sensor. I want to spin a plate around and send >out burst of data (PIC to PIC communication) 45 or 90 degree increments >(ie send out a burst at: 0 degrees, 90 degrees, 180 degrees, 270 degress) >I was think of using the hall effect sensor to sync up when I reach >0 degrees (cheaper than a stepper motor....I think). Probably. > > >> Urr, are you using an integrated chip/display? These offer differing >> address modes serial/nibble/byte sometimes. Only other reason to read >> would be to do a dump of the contents of the display, or the char gen - with >> a view to doing read/modify/write to either one. > >I would be using a standard integrated chip/display (Sharp or Seiko or >Optrex 2 x 16 LCD display) > Minimise io by using in nibble or serial mode. Don't know the specs on those displays off the top of my head. > >> clear wdt. eg latter case - if you have noise prone design micro can latch >> up so a s/w reset won't fix - or brownouts will stop it working too. If its >> a life or death thing (and it better not be - it can't checksum itself) then >> an external wdt is the way to go. > >The DS1232 is a micromonitor chip which will provide 3 functions: > 1) Power monitor for brown outs. > 2) Watchdog > 3) Push button reset >Any of the 3 conditions will produce a 250mS reset pulse. I wish to do >all three. I wouldn't assume that a reset would reset. As I saw someone observe about *a* microcontroller (no names) - "The reset is sort of a software request for a reset" ... > > >>> 2) The timer for PIC to PIC serial >>> communication >> >> Async (RS232) or sync? The latter is probably easier and faster. If you >> dont need speed, you could put both on i2c bus - it is multi-master. (but, > >I will be doing sync communication. I just want to use 2 lines (data & gnd) >as I may want to do this over an RF link in the future. I not using RS232. >Speed is not really a concern. I bought "Easy Pic'n" and "Pic'n up the Pace" >and PIC to PIC communication is implemented by using the timer. I thought >perhaps I could use this. But of course I am open to better or alternate >ways of achieving this. > > >I guess my main question was can I do all three items as they all use >the timer in some way. Possible, but difficult. You can sometimes use the timers for more than one thing in an application, but you've got to do some switching of values and adding fudge factor sometimes. I'd say avoid unless you really need to, counting cycles to achieve timing is easy on the PIC. > > >> You're using a connector to connect to your ICP, right? How about making it >> something like a 10 way dil ribbon connector. When not in program mode use >> links to route thru to your regular cct. Its a lo tech soln, but sometimes >> they are ok. Depends on skill of assemblers. > >I guess I'm going overboard. I was thinking of the circuit automatically >switching to ICP mode once the connector was plugged in and switching back >to normal mode with the connector removed. I'm using an 8 position RJ45 >connector as the ICP port. Expensive once use socket. Still, I guess tinsel cable is robust. > >I have since given up the automatic mode and installed 2-position jumpers >to isolate the circuit. > > >> What IS it? > >If I tell you....... I will have to kill you! ;) Or get an Oz Piclist member to do it for you. >Just kidding, it is actually a remote data logger/transmitter. Duh! Deja Vu from some of my past occupations! > > >> If i2c is not for you, let me know, and I'll see where the mux techniques >> lead. > >Still thinking about mux as I don't know too much about I2C. Can you >send info please. > Don't expect it till the weekend. Working fulltime days now, which restricts somewhat. But have a think about I2C it would probably save you a lot of 'glue' logic chips... MikeS <RemoveMEmikesmith_ozspamBeGonerelaymail.net>

Mike Smith wrote: > > -----Original Message----- > From: Randie Ohtsji [4555] <spamBeGonerohtsji@spam@spam_OUTGLENVAN.GLENAYRE.COM> > To: TakeThisOuTPICLISTspamMITVMA.MIT.EDU <PICLISTEraseMEMITVMA.MIT.EDU> > Date: Tuesday, 21 October 1997 8:14 > Subject: Re: What is the best way to sense a pushbutton press??? > > <snip> > > >P.S. [OT] I just met with our Microchip rep and he was saying other Flash > >parts are due in 2Q98 - 3Q98. He's never heard of Scenix. > > An ostrich, methinks. They are following the ostrich *principle* (head under the ground) until next year, when they'll need an *obstetrician* to get the Flash out of them. So, until then, it is our duty to ostracize them at every opportunity. -- Friendly Regards Tjaart van der Walt RemoveMEtjaartEraseMEspam_OUTwasp.co.za _____________________________________________________________ | WASP International http://www.wasp.co.za/~tjaart/index.html | | R&D Engineer : GSM peripheral services development | | Vehicle tracking | Telemetry systems | GSM data transfer | | Voice : +27-(0)11-622-8686 | Fax : +27-(0)11-622-8973 | | WGS-84 : 26010.52'S 28006.19'E | |_____________________________________________________________|

Hi Randie (Randie Ohtsji [4555]), in <@spam@199710171738.KAA15419RemoveMEEraseMEglenvan.glenayre.com> on Oct 17 you wrote: > Yes, I am using an old version of OrCAD (v4.???). I'm very new to > the PIC, but I have a 16C84-04 and a 16F84-10 to play with. This > PIC list is great -- I found out a lot from all the email bouncing > around (but I still have a LOT to learn). I would appreciate > any hints, circuits, starting points, etc. > > I want to connect a 2x16 line LCD (8 data lines + 3 control lines), > a fully addressed ISD voice chip (10 address lines + 3 control > lines + 2 status lines), compass module (1 data line + 4 control > lines), serial communication (PIC to PIC: 1 data line + gnd). > 3 or 4 push buttons, Hex rotary switch - BCD format (4 lines) > and 2 or 3 misc I/O (2 or 3 lines?). Also maybe some motor control > lines and a data line for hall effect sensor (to keep track of motor). > If there is enough I/O, then maybe control the LCD contrast with > digital pot (4 lines?). Digital volume control would be nice too > (4 control lines - using a digital pot???). I don't want to disappoint you but your requirements of IOs superceeds the '84 capabilities. Also considering that you probably want to display some text messages on your display (which have to be stored somewhere with your program) I'd head for an 8051 or AT89C52 (if internal program memory is required). There are lots of free development tools and the AT89C52 can store up to 8kb of program (lots of space for text messages compared to '84 1kb). If you insist on using a PIC, there are some TTL serial to parallel converters that you can use to interface lots of IO to few port pins. Or you can use latches. I think the '84 is underpowered for your project. > Does the PIC need to read data FROM the LCD. I know that bit 7 needs > to be read for the LCD busy flag, but do the rest of the lines need > to be accessed??? You usually don't need to read, or even poll the busy flag. Just use the max timing from your datasheet. > I wish to do a few custom graphic characters in the > LCD (an Up and Down arrow.....funny that they don't have these, as > there is a left and right arrow in the character set). I think that I > am allowed to create up to 8 custom characters???? Usually you can define the arrows (btw 8 custom chars already require 1/16 of '84 code space, not including upload code). > A) I wish to use: 1) The internal watchdog > I was thinking that if I can't, then maybe > using an external watchdog & power sense > chip (Dallas DS1232). The internal watchdog does not protect you from brownouts. If your device is to work unattended you should use a 1232!