Other tricks that might be helpful: - for another alternating bits sequence, repeatedly send capital letter "U" (a different sequence of alternating ones and zeros). - for a long pulse, set the baud rate to the slowest speed that the serial port supports and then send 0x00 or send 0xFF
On Wed, Aug 2, 2017 at 11:47 AM, Mike Stein <mhs.st...@gmail.com> wrote: > Good advice; the most likely culprit (because it's indirectly connected to > the outside world with its static, lightning, ground loops etc.) is M35, a > (1)4584. > > The only other IC would be M24, a 40H032 (which could probably be replaced > with a 74HC(T)32). > > m > > ----- Original Message ----- > From: "John Gardner" <gof...@gmail.com> > To: <m...@bitchin100.com> > Sent: Wednesday, August 02, 2017 12:23 PM > Subject: Re: [M100] Model 100 serial port > > > > ...the problem is somewhere between the db25 and the UART... > > > > Most likely. I'm no great troubleshooter, but if I may... > > > > Set up a test file which contains a long series of 0xAAs, as in > > > > 10101010... > > > > Send the file at a baud rate which is easy for you to see with > > > > whatever you've got for test equipment. > > > > While the file is being sent, look for the signal. When you find it, > > > > the fault is between that point & the DB25. I expect the problem > > > > is either a PCB trace, solder joint, a defective buffer, or the DB25 > > > > connector itself (It happens...). > > > > There's also a small possibility that the UART is at fault, but not > likely. > > > > I'd be interested to hear what you find. > > > > > > > > > > > > On 8/2/17, John R. Hogerhuis <jho...@pobox.com> wrote: > >> Well the good news is the problem is somewhere between the db25 and the > >> UART :-) > >> > >> -- John. > >> >
