A DPLL would be great if I could ensure edges at any reasonable interval. I cannot because I don't control the protocol. Luckily I know: 1: the sender is using an accurate (and precise) crystal controlled clock in a room temperature environement. 2: I am using an accurate (and precise) crystal controlled clock in a room temperature environment. 3: Time moves at the same rate everywhere in the universe ( :-) ) So... I luck out. In fact, in this application a DPLL would probably be a _bad_ idea because the data is fed thru 202 style (FSK) modems which can really shift the edges around quite a bit on the detector side. Thus, the detector could get easily confused and off frequency. So, I just watch for the start bit, guess where it's middle is, and start sampling away at one-bit-time intervals. btw: In the real-world application I get almost perfect comms over (100?) miles of phone wire. Bob Ammerman RAm Systems (contract developer of high performance, high function, low-level software) ----- Original Message ----- From: Marc To: Sent: Thursday, July 13, 2000 5:10 PM Subject: Re: [EE]: RS232 error > > I had an application that required receiving an async serial data stream of > > an unusual structure: 1 start bit + 240 data bits + 2 stop bits. Obviously > > This type of data is very difficult to receive with a normal UART. > > My suggestion for such applications is not only to use accurate timing, but > also to use a DPLL receiver. One that looks for bit edges where it expects > them to be, and adjusts its timing when it detects the edges to be off. When > your data is guaranteed to have edges every now and then, you can receive > telegrams of any size. > > Note by the way that with symbols of that size, even weak edges can upset > the timing, making the product flakey with long cables or wireless transmission. > The inherent adjustment of a DPLL can fix a lot of problems. > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]: PIC only [EE]: engineering [OT]: off topic [AD]: advertisements -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]: PIC only [EE]: engineering [OT]: off topic [AD]: advertisements