On 1/18/07, peter green wrote: > > > > -----Original Message----- > > From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu]On Behalf > > Of Vasile Surducan > > Sent: 18 January 2007 06:26 > > To: Microcontroller discussion list - Public. > > Subject: Re: [PIC] Cheap programmer interface, was noob's 1st ques > > > > > > On 2/3/06, Alan B. Pearce wrote: > > > >I'm not sure I get this yet... What's wrong with > > > >using the modem pins of a serial port? Or is this > > > >what you are thinking of using? > > > > > > That is exactly what he is wishing to do, but part of the discussion has > > > revolved around how timings are unreliable when using > > USB-Serial interfaces. > > > > > > Personally I suspect the most reliable way to do it would be a > > USB-Printer > > > port set up as a basic text only printer, and then fed repeated > > characters > > > with one bit of the ASCII character being the clock, and one > > bit the serial > > > data. Still does not give the feedback path, and would probably > > need three > > > characters to clock one bit into the chip. Also if you streamed > > the data out > > > the port, the chip may FIFO buffer it, and stream it into the > > chip too fast > > > for it to write to the Flash. > > > > Alan, what makes you think the USB/parallel is working different than > > USB/serial conversion ? The frames for sending a command word from USB > > to the USB transciever takes the same (too long) time. > > You have no timing control between ASCII caracters sent. > no but you do have the ability to send dummy characters that produce no transitions with this system. > > you'd also have to deal with the handshake lines on the port (iirc paralell handshakes every character but i'm not sure what handshake mechanism it uses), you may be able to add some delay here fairly easilly too (say a resistor, a capacitor and a schmitt trigger). You didn't understand me. There is no difference in handshake mechanism allowed by the USB transciever for serial or parallel jobs as long the problem is the USB protocol itself. Please read here: http://www.beyondlogic.org/usbnutshell/usb6.htm greetings, Vasile -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist