You're right, the smt versions are a bit larger. The smallest ones I've seen are the same footprint as the t/h versions--they just have a tab at each end or the leads are folded over and held in place with a plastic spacer. I'm helping to close down a major auto manufacturer instrument cluster line, and they have a 4 mhz xtal in a flat pack but the footprint is actually larger than the t/h version. Go figure. Whatever you specify, just make sure you can second source them. Digikey has what looks like a small one p/n XC587CT-ND $1.95 single qty. that looks good. http://ecsxtal.com/pdf2/CSM-12.PDF Rick Lawrence Lile wrote: > I've been trying to specify some surface mount crystals. I have two on my > board, one a 4MHz and one 32.768 khz. > > Now, the thru-hole 4 MHz crystals come in a pretty big can, the standard > HC-49U package. The thru-hole 32 kHZ cryustal comes in a tiny little can > looking about half the size of a 1 uF Cap. > > In surface mount, I have only been able to locate crystals in gargantuan > packages that look like HC-49's with saurface mount tabs on the bottom. The > surface mount 32 khz crystal is actually *bigger* than the thru hole 32khz > crystal, by about 10X. I am not used to buying surface mount parts that are > *bigger* than thru-hole. Kinda like a subcompact car longer than a > Caddilac. > > What type of crystals do you folks use on surface mount projects, and how > small do they get? > > --Lawrence > > ----- Original Message ----- > From: "Rick C." > To: > Sent: Monday, June 10, 2002 4:16 PM > Subject: Re: [PIC] - Serial Woes and Crystals > > > 20 mhz resonators aren't accurate enough for standard serial baud rates. > Yes, > > you need 2 caps on the xtal and almost any of the ones Digikey sells will > work. > > The MAX232 doesn't have anything to do with your problem unless your > interface > > isn't inverting the logic or you have other circuit issues. I have a > bullet > > proof routine for bit banging if you need it. Only about 50 bytes of > > instructions to send and receive data. > > Rick > > > > Rex Byrns wrote: > > > > > You guys have been a great help, the picusart.zip and the other serial > > > routines have been great, but I am having ZERO luck getting them to > work. > > > > > > The bitbang method is a method is a variation on > > > http://www.piclist.com/techref/piclist/cheapic/alpha4m.asm . > > > > > > I used the formula from the code to get the timing right. I have only > tested > > > the send routine, and I tried using Hyperterminal in 'view data' mode. > I > > > also tried the mscomm control in VB6. I get nothing with both. > > > > > > One of the problems is that I am using a 20mhz resonator on both chips > > > (16f84a & 16f628) > > > I would really like to get a bitbang routine to work with the 16f84 and > the > > > USART going on the 16f628. 4mhz is the fastest 'proven code' that I have > > > found. I don't really know what I am doing wrong and would love to have > > > code that is proven, so I can rule out hardware issues. I have seen > several > > > formulas for baudrate, my resonator seems to be off several milliseconds > > > (using Roman's on the dot 1 second routine). Between these two margins > of > > > error, not counting my inexperience, I am stuck. > > > > > > Should I just go ahead and buy a couple MAX232? Like digikey # > 296-1402-5-ND > > > ? > > > For only $1.30 for the TI brand it's not bad. > > > > > > I would also like to order a 20mhz crystal, but don't know which one. Do > I > > > need caps? > > > > > > Thanks again. > > > > > > -- > > > http://www.piclist.com hint: To leave the PICList > > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > -- > > http://www.piclist.com hint: To leave the PICList > > mailto:piclist-unsubscribe-request@mitvma.mit.edu > > > > > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads