Parport to 7i92

Ok
On my new LinuxCnc computer, added a second hard drive and installed Win10. Dual boot. So now exactlty the same hardware.
Booting on Win10, with SpindleTalker2 I have everything working well : Com1, 8 bits, 9600bds, 1 stop, no parity
Logic analyser capture on Rs232 pins Rx, Tx, Dtr Rts (see:SpindleTalker2.png)

Reboot on Linux

loadusr -W hy_vfd -d /dev/ttyS0 -r 9600 -b8 -pnone -s1  -t1 --debug
setp hy_vfd.enable 1
Comms error (see IMG_20220704_232136.jpg)

But the LinuxCnc and the analyser agree on Tx data :0x01 0x01 0x03 0x05 0x00 0x00 0x2C 0x4F
But on Rx they don't display the same data
The analyser sees 8 bytes incomming, no framing error.( LinuxCnc.png ) The same query occurs every 600ms and the same response.
LinuxCnc expects 8 bytes, only detects 6 and not the sames values

There's an other difference SpindleTalker and LinuxCnc don't drive Dtr Rts the same way.

The more I work on this, the less I understand

I did try all the possible comm settings. The vfd send response only when it matches the driver settings. Obviously
But always the same comm error on incorrect number bytes received.

I will try to disconnect Dtr from my pc com port and force it to Gnd to have the same level as SpindleTalker2. Regarding the rs485 adaptor schematic, it is used

I make it run !!!

I cut the link to the Rs232 port of the PC to the Rs485 adaptor on RTS and DTR.
I straped RTS to Gnd to be in the same state as SpindleTalker2 and it's working !!!

Maybe hy_vfd does not set up the serial port the same way as SpindleTalker2 does? It is possible to use stty to enable/disable RTS/CTS handshaking on the serial port (see 'man stty'), but I'd think those settings would be overridden by any program actually using the port later. Anyway, serial ports and their myriad of settings have always been a mystery to me under Linux... Good job of getting it working!

From the sources (hy_comm.c) , no hardware flow control enabled