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