Post by thread:[PIC] Select a chip and programmer for first proje

Here's my first project: My wife has an espresso machine and she wants a timer to turn it on in the morning. It uses rubber pad switches to turn on/off. Holding the switch pad down for 4 seconds turns it on (if it's off - otherwise it enters programming mode). Holding it down for 2 seconds turns it off (if it's on - otherwise it does nothing.) The voltage on the on/off switch pad is 5 volts on side 1 and ground on the other side. About 0.5 ma flows when the switch is closed. I'm guessing the machine uses a microcontroller (to control temps, flow rates, timing, etc.) , and I'm looking at a switch that has a 5 volt pullup connected to an input to detect when the switch is pressed to drop it low and for how long. I can't easily get access to the microcontroller, but I can get to the on/off switch. Here's what I'd like to build - A separate PIC microcontroller to turn on/off the espresso machine's on/off switch. The separate PIC microcontroller runs an LCD clock display with pushbutton switches to set the clock time, a master reset switch and a switch to cycle through displays of clock time, on time and off time. When the on time arrives, the PIC sends a 2 second pulse to turn it off (in case it's on) then a 4 second pulse to turn it on). When the off time arrives, it just sends the off time. I don't have direct access to 5 volt power, so I think it will be battery powered. If I can sneak 5 volt power off the machine, battery backup would be nice. I've looked at the Microchip App Note AN582 Low-Power Real-Time Clock that uses an Hitachi 2 x 20 LCD display. If I use the same, I figure I'll need 7 outputs for the display, and 4 switch inputs (select units to change, increment units, zero seconds reset and select clock/on_time/off_time display), and it looks like MCLR is used for a master reset. I have some assembler programming experience, and I've studied a few PIC listings. I know I'll need to try some "hello world" basics before building this, but I'd appreciate some comments: What chip might be good to select for this ultimate design? Something with lots of sample programs on the web I can look at would be good. Not too expensive, for when I screw up. Any sample code for clocks with timer alarms would be helpful, there must be several of those. Can you suggest a programmer. I've seen something called the No Parts Programmer, that uses a parallel port running under DOS. I've got various computers from Debian/Linux to W98 to WXP. I've got an older UV eraser and EPROM programmer that I can at least scavenge the 40 pin ZIF from. It might be nice to build something, but buying is OK if not too expensive. Is it likely I can scavenge an LCD display from an old clock/phone, or will they be custom and need more inputs/outputs than I have. Thanks for your comments.

>I've looked at the Microchip App Note AN582 Low-Power >Real-Time Clock that uses an Hitachi 2 x 20 LCD display. >If I use the same, I figure I'll need 7 outputs for the >display, and 4 switch inputs ... > I know I'll need to try some "hello world" basics >before building this, but I'd appreciate some comments: Haven't looked at the app note, but this sounds reasonable. >What chip might be good to select for this ultimate design? >Something with lots of sample programs on the web I can look >at would be good. Not too expensive, for when I screw up. >Any sample code for clocks with timer alarms would be >helpful, there must be several of those. You do not say what chip the app note uses, but I would suggest that a 16F876 or 18F252 (or the later versions of it) would probably be the way to go. Also note that you may be able to get some chips as samples from Microchip. >Can you suggest a programmer. I've seen something called >the No Parts Programmer, that uses a parallel port running >under DOS. A lot of people have problems with these for various reasons. >I've got various computers from Debian/Linux to W98 to WXP. Check out the programmers available from Olin http://www.embedinc.com/easyprog/index.htm or Wouter http://www.voti.nl/shop/catalog.html (look for Wisp628) which provide extensive features for hobby use. These will save you a heap of potential problems getting going, and allow you to be pretty certain that you have programmed the chip correctly. >I've got an older UV eraser and EPROM programmer that I can >at least scavenge the 40 pin ZIF from. It might be nice to >build something, but buying is OK if not too expensive. With the Flash memory parts you will not need a UV eraser, and the parts can be programmed in circuit (with a little care in setting up the circuit). >Is it likely I can scavenge an LCD display from an old >clock/phone, or will they be custom and need more >inputs/outputs than I have. I have scavenged displays equivalent to the ones you mention are used in the app note, from FAX machines. Any other item using a similar sort of display is likely to be using these as well, although one does need to be a bit careful with pin connections, as some end up being effectively back to front because of the way the display PCB is laid out. If the display is a fully graphic one it may also be useable if the controller is on a PCB that is part of the display, as it is again likely to be a second source of a well known chip.

Todd Pattist wrote: > Here's my first project: My wife has an espresso machine and she wants > a timer to turn it on in the morning. It uses rubber pad switches to > turn on/off. Holding the switch pad down for 4 seconds turns it on (if > it's off - otherwise it enters programming mode). Holding it down for 2 > seconds turns it off (if it's on - otherwise it does nothing.) Wow, that has got to be one of the worst user interface I've ever heard of. > The > voltage on the on/off switch pad is 5 volts on side 1 and ground on the > other side. About 0.5 ma flows when the switch is closed. Good. This means you can put a NPN transistor in parallel with the switch. {Quote hidden}> I've looked at the Microchip App Note AN582 Low-Power Real-Time Clock > that uses an Hitachi 2 x 20 LCD display. If I use the same, I figure > I'll need 7 outputs for the display, and 4 switch inputs (select units > to change, increment units, zero seconds reset and select > clock/on_time/off_time display), and it looks like MCLR is used for a > master reset. I have some assembler programming experience, and I've > studied a few PIC listings. I know I'll need to try some "hello world" > basics before building this, but I'd appreciate some comments: > > What chip might be good to select for this ultimate design? Something > with lots of sample programs on the web I can look at would be good. Just about any PIC will do here. It seems you're only asking for about 12 I/O lines. However, you won't want to buy just one PIC and they are cheaper if you buy a handful, so I suggest a PIC that will be good for other projects too. It sounds like a PIC in the standard 18 pin footprint will be fine. In that case I would go for the 16F648A or 16F88 as these are the biggest bestest in the 16 family with 18 pins. > Not too expensive, for when I screw up. That actual PIC price will be relatively little compared to all the other project costs. > Can you suggest a programmer. You should be thinking about how you're going to debug this. For that the ICD2 is the best answer as it's a programmer too. > I've seen something called the No Parts > Programmer, that uses a parallel port running under DOS. All those "no parts", "El Flako", and other programmers without a controller are going to be frustrating, especially when things don't work right and you don't have the experience to take a good guess at which of the 20 possible reasons it is. If you really want just a programmer, consider my EasyProg (http://www.embedinc.com/products) or Wouter's Wisp. > I've got an older UV > eraser and EPROM programmer that I can at least scavenge the 40 pin ZIF > from. Other than that, maybe a museum would want it. ****************************************************************** Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC consultant in 2004 program year. http://www.embedinc.com/products

On Mon, 19 Dec 2005, Todd Pattist wrote: {Quote hidden}> Here's my first project: My wife has an espresso machine and she wants > a timer to turn it on in the morning. It uses rubber pad switches to > turn on/off. Holding the switch pad down for 4 seconds turns it on (if > it's off - otherwise it enters programming mode). Holding it down for 2 > seconds turns it off (if it's on - otherwise it does nothing.) The > voltage on the on/off switch pad is 5 volts on side 1 and ground on the > other side. About 0.5 ma flows when the switch is closed. I'm guessing > the machine uses a microcontroller (to control temps, flow rates, > timing, etc.) , and I'm looking at a switch that has a 5 volt pullup > connected to an input to detect when the switch is pressed to drop it > low and for how long. > > I can't easily get access to the microcontroller, but I can get to the > on/off switch. Here's what I'd like to build - A separate PIC > microcontroller to turn on/off the espresso machine's on/off switch. > The separate PIC microcontroller runs an LCD clock display with > pushbutton switches to set the clock time, a master reset switch and a > switch to cycle through displays of clock time, on time and off time. > When the on time arrives, the PIC sends a 2 second pulse to turn it off > (in case it's on) then a 4 second pulse to turn it on). When the off > time arrives, it just sends the off time. I don't have direct access to > 5 volt power, so I think it will be battery powered. If I can sneak 5 > volt power off the machine, battery backup would be nice. > > I've looked at the Microchip App Note AN582 Low-Power Real-Time Clock > that uses an Hitachi 2 x 20 LCD display. If I use the same, I figure > I'll need 7 outputs for the display, and 4 switch inputs (select units > to change, increment units, zero seconds reset and select > clock/on_time/off_time display), and it looks like MCLR is used for a > master reset. I have some assembler programming experience, and I've > studied a few PIC listings. I know I'll need to try some "hello world" > basics before building this, but I'd appreciate some comments: > > What chip might be good to select for this ultimate design? Something > with lots of sample programs on the web I can look at would be good. > Not too expensive, for when I screw up. Any sample code for clocks with > timer alarms would be helpful, there must be several of those. > > Can you suggest a programmer. I've seen something called the No Parts > Programmer, that uses a parallel port running under DOS. I've got > various computers from Debian/Linux to W98 to WXP. I've got an older UV > eraser and EPROM programmer that I can at least scavenge the 40 pin ZIF > from. It might be nice to build something, but buying is OK if not too > expensive. > > Is it likely I can scavenge an LCD display from an old clock/phone, or > will they be custom and need more inputs/outputs than I have. > > Thanks for your comments. > Do check out http://www.glitchbuster.com. His prices for single chips are probably unbeatable, and his shipping and handling is only $1.85. Also, I believe he will burn a program in a chip for 20% of the chip price. You could use the PIC16F88 bootloader from http://www.sparkfun.com and get away with not buying a programmer at all. See Sparkfun tutorials for what a bootloader is. Also, if you want a cheap programmer you can check out sparkfun or http://www.phanderson.com, Peter Anderson also charges very low S&H prices. Have Fun, Kevin P.S. No affiliation to the above, just a satisfied customer.

part 1 1738 bytes content-type:text/plain; (decoded 7bit) > time arrives, it just sends the off time. I don't have direct access > to 5 volt power, so I think it will be battery powered. If I can > sneak 5 volt power off the machine, battery backup would be > nice The machine may or may not have a transformer supply, which would be the safest to use. If it doesn't, you can tap off whatever it's using to power the micro or, less ideally, make your own http://home.clear.net.nz/pages/joecolquitt/txlesspsu.gif BE AWARE THAT WORKING WITH A CIRCUIT LIKE THIS CAN BE DANGEROUS AND YOU SHOULD USE AN ISOLATING TRANSFORMER > Any sample code for clocks with timer alarms would be > helpful, there must be several of those Purely internal time-keeping is not too difficult. You just need a few registers for hours, minutes, seconds and ticks (ie an IRQ counter). Add a few more for output to a display. Any PIC will have more than enough RAM for this. The source for IRQs can be primarily mains cycles, which will be the most accurate, and secondarily a 32kHz xtal on TMR1 for when mains power is off. You'd want mains to be present most of the time, as plain xtals do drift. Maxim/Philips have RTCs that are pretty stable. eg http://www.maxim-ic.com/products/timers/real_time_clocks.cfm but for this application you don't really need a calendar IC. See the attached gif. It has most of the bits that you need. The PIC monitors the "Vsense" line to know when mains is there. If it is, then mains cycles (ticks) are counted. If it isn't, the 50Hz TMR1 IRQ takes over. The "ticks" counter counts down from d50 to d00, at which point "seconds" is incremented, "ticks" is re-loaded with d50, and so on part 2 13563 bytes content-type:image/gif; (decode) part 3 35 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)