I hope it will help someone...
I bought a replica 1 ten from Vince Briel but it never really worked :(
each time I had a hand near the board I had an apparent repeated reset
the machine displaying
finally I discovered the source of the problem some noise received by the strobe pin (pin 40 6821)
I solved it by adding a 10k resitor on the back of the board between PIN 1 (gnd) and pin 40 (CA1/strobe) of the 6821
now it is parfaitly stable...
the problem is more complex, in fact the propeller code is puting the direction port of the proppeller in output to send a character
to the PIA and then put it back in input mode
so we have CA1 in input mode and most of the time strobe on the propeller in input mode
in that case CA1 is receiving noise.... (the 10k resistor works)
it is possible to avoid adding a resistor by modifying the propeller code to let the direction port in output mode
but in that case it breaks the ascii keyboard port
I tried to removed the 10K resistor I added and flashed the propeller with last code from Reactive micro
modified to have the keyboard direction pin always on output... it works perfectly
the machine is rock stable but the ascii keyboard port is unusable
I try to find a better fix
by tweaking the propeller code I have been able to push it to 3Mhz and 57600 bauds
does anybody know if there is a way to automatically convert lowercase into uppercase in the propeller code ?
it's boring to use shift or caps lock all the time to type a program
(lower cases are simply ignored)
Finally to keep the same functionality
the best fix for the noise on strobe is the 10k resitor on the back of the PIA between pin 1 and 40
I have not found any way to modify the spin code without loosing the ascii keyboard
for the use of lower case in place of upper case I just added:
if serdata > 96 and serdata < 123
serdata -= 32
just before sending the data to the PIA
in file: replica 110REV03.spin
once the strobe problem was fixed I discovered that from time to time I had a garbaged screen
this garbage appeared in conditions similar to the strobe noise
it is due to the DA line going up and down
I solved this problem by adding a 10k between DA line pin 17 PIA and GND pin 1 PIA
after having done this 2 modifications the machine is working fine and I've not seen any new sources of noise
I have the same problem but even with putting the resistors on 1-40 and 1-17 i am still seeing the / / / and then it scrolls off the screen. when i use the serial adapter via USB i don't see the characters and the replica1 is fairly stable minus the occasional minor glitch.
I ended up actually replacing the USB powerconnector on the unit and once done all my problems went away. This was my first project i put together and at the time wasn't perfect with my soldering but thousands of solders later one does get better at it.. but again, replacing the USB board and the 2 pin header strips solved all my odd issues..