RS485 and SN75176A typo ?

Dear reprapers

After some headacke of troubleshooting my serialbus ive managed to figure out that the reprap wiki must have a serious flaw.
According to the Wiki you should use a SN75176A för RS485 communication , but according to the datasheet the chip doesnt support RS485 but it does support RS422, is this a typo or did someone miss the difference between SN75176A and SN75176B ?

My initial test ive been running a SN75176B on my mobo and apparently a SN75176A on my extruder board (assembled from makerbot)

Comms work in windows until i try to print anything, then it crashes with linenr+1 error or checksum issues
on linux on the other hand it NEVER works. complains like a bitch about comms not working but as i look at the debug i see sometimes the temp values flash by.

If anyone is wondering why im using the B unit the local store / retailed apparently dont stock SN75176A but SN75176B on the otherhand....

RS-485 is a differential half-duplex electrical signalling spec. SN75176A has high-z output capability so it should work just fine. The datasheet even shows it being used on an RS-485 line (figure 15). The main difference between RS-422 and RS-485 is that you can only have one driver on an RS-422 line - that is, it doesn't support half-duplex.

Why does this chip not mention RS-485 in its datasheet? I truly have no idea.

As long as the chip you use has the same pinouts (and it looks like they do), it should also work fine- you may even be able to have an A on one board and a B on the other board

---

-----------------------------------------------
Wooden Mendel
Teacup Firmware

odd thing is that the serial miss behaves and what i understand from the firmware the serial is only used to transmit temp related info and extruder instructions, or am i wrong on that assumption ?

The comms that you report is misbehaving is the connection between the motherboard and the PC, nothing to do with the RS485 link to the extruder.

---

[www.hydraraptor.blogspot.com]

apparently in linux it is the com from the computer to the reprap (same error if i unplug cable entirely) but still doesnt explain issues in windows cause it works ?

i can tell the XYZ and extruder to move this alone would indicate that the connection is good from the pc to the reprap unless i have a WIFI ghost living in my reprap + windows pc.

when i try to print the reprap moves like it should but the extruder doesnt operate once the error occur. (linenr+1

error: GCodeWriter.waitForResponse() - dud response from RepRap.Serial Error: lineNr is not the last lineNr+1
error: GCodeReaderAndWriter.getBTemp() - no value stored!
error: GCodeWriter.waitForResponse() - dud response from RepRap.Serial Error:Recieved a LineNr code without a Checksum code or Checksum without LineNr <---- happens every 10th error ?

i can see a readout from the extruder temp once every 10th? line (and this is linux not windows) on win this work until i try to print then it goes apeshit and crashes ;P

Edited 2 time(s). Last edit at 08/26/2010 03:12PM by PimpKittah.

Quote

error: GCodeWriter.waitForResponse() - dud response from RepRap.Serial Error: lineNr is not the last lineNr+1
error: GCodeReaderAndWriter.getBTemp() - no value stored!
error: GCodeWriter.waitForResponse() - dud response from RepRap.Serial Error:Recieved a LineNr code without a Checksum code or Checksum without LineNr <---- happens every 10th error ?

RepRap GCode specs insist on line numbers being consecutive and lines with a line number must have a checksum also.

I've removed such checks in FiveD on Arduino firmware, but I'm currently unsure wether this firmware compiles out of the box and/or which changes are required for Generation 3 electronics (or later) to get a working machine. I'm currently using the july 23 revision on an extruder-less (milling-)machine with Generation 2 electronics.

---

Generation 7 Electronics	Teacup Firmware	RepRap DIY

i dont know if this is the fix or just a act of random functionality (probably the latter one)

but ive tampered with the firmware to run on default baud 38400 instead of 19200 and also changed the setting in the software. As of now it doesnt crash in windows when i try printing something, (running my first print now )

but still its kinda odd that i get this error in linux 100% of the time and only when i tries to print in windows.