Posted
·
Edited by jhauxwell The schematic had a mistake
Hi,
I realise this is an old thread but hoping someone might be able to help.
I have made a handmade Railcom decoder but suspect there may be an issue somewhere and I'm not sure what to do next.
I have hooked up a scope to the INT and data and the result is as follows.
INT is the blue top trace, RX is the red trace - I separated them vertically for clarity.
What I don't understand is that the data from the locomotive seems to be arriving just before the cut-out starts... i thought the whole idea was that it is the cut-out that allows the decoder to talk back. Its almost as is the cut-out is being delayed,
Looking at the spec, it should all happen inside the cut-out:
Here is the detection part of of my circuit. All the voltages are correct, and as you can see from the trace, the data is actually good (and i have manually decoded the hex coming back and it is correct for the locomotive on the track)
If anyone has any ideas id be really grateful.
It seems that I need to use the cut-out period as a way to start the serial reads and while the the two aren't arriving as expected in time that isn't going to work.
Handmade RailCom
in Computer Control
Posted · Edited by jhauxwell
The schematic had a mistake
Hi,
I realise this is an old thread but hoping someone might be able to help.
I have made a handmade Railcom decoder but suspect there may be an issue somewhere and I'm not sure what to do next.
I have hooked up a scope to the INT and data and the result is as follows.
INT is the blue top trace, RX is the red trace - I separated them vertically for clarity.
What I don't understand is that the data from the locomotive seems to be arriving just before the cut-out starts... i thought the whole idea was that it is the cut-out that allows the decoder to talk back. Its almost as is the cut-out is being delayed,
Looking at the spec, it should all happen inside the cut-out:
Here is the detection part of of my circuit. All the voltages are correct, and as you can see from the trace, the data is actually good (and i have manually decoded the hex coming back and it is correct for the locomotive on the track)
If anyone has any ideas id be really grateful.
It seems that I need to use the cut-out period as a way to start the serial reads and while the the two aren't arriving as expected in time that isn't going to work.
Thanks,
Joel.