Serial port driver for the MESA 7i96?

Greetings,

I am working on a 24" x 24" engraver retrofit project. The reason being, the original driver for it was basically a printer driver, which is quite limited as a CNC controller. This machine has a 1HP spindle motor that is controlled by a Toshiba VF-S9 inverter. I would like to interface it with LinuxCNC using the MODBUS protocol.

I started this project with a MESA 7i96 because I have an older decommissioned iMac Core 2 Duo that I wanted to use. (As an aside, this is working nicely so far; Linux Mint 18, Preempt-RT kernel, 22000 max latency, if I keep the wifi off.)

I am using about half of the I/Os on the card so far. My question is, is it possible for the card to expose some pins as a serial port?

If this is not possible, my other option is to use a USB-Serial adapter. Are there issues with these kinds of adapters for spindle control?

I am referring this documentation: VFs11 driver

The documentation refers to a wiring schematic for converting the link to RS232. Unfortunately, the links to those schematics are broken. Could anyone provide those again here?

Thanks!

This was a while ago, but regarding the 7i96, Andy said:

"The existing RS485 port can be used (you would need a firmware that puts a UART on those pins in place of the smart-serial module) and also some of the pins on the expansion port could be re-allocated (by a firmware change)."

How would I go about getting this firmware? Do I have to write VHDL source code myself and reflash the FPGA? (geez, I hope not)
The reason I ask is that I would like to control my Huanyang GT series VFD via RS-485 directly from the 7i96 board. That is, without a USB to RS-485 dongle.

Theres standard firmware for this but no driver

7i96_pktd.bit

I notice that a new hal type has been added that
might make writing a clean hal interface to the UART easier:

hal_port

Thanks, this may be beyond my capability but I will investigate further. Were those references intended to be URLs?

Can you just put jumper wires on the pins in the p1 expansion connection, io34 - io50? Or is it not recommended as they wouldn't be protected this way without an actual expansion card?

You can, but its like a bare parallel port.
If you connect to a voltage outside the range of about -0.8V to 7V
you will destroy the bus switch and possibly the FPGA.

You can use one of the cheap "5 AXIS MACH" breakout boards to
protect the I/O

If you use bare pins, include a 220 Ohm or so series resistor to protect the
negative input clamp diodes from excessive current.

I have made good progress (at least for me) but can't seem to get past how to connect to the uart in the 7i96. I wrote a userspace hal component that communicates with the VFD via a module that assembles and disassembles modbus packets. This works well using a fake uart routine. The example mesa_uart.comp isn't helping me at all and I can't find anything about pkt_uart in the linuxcnc source files on github. So, the question is - how do I connect the assembled modbus packets to the uart in the 7i96? Also, are there specs for pktuart somewhere? Any help is appreciated.
Thankyou.

I did not mean to imply it was a bad example. I'm sure it is a good example. After re-reading the above posts, it appears that my stock 7i96 does not include a UART and I would have to re-flash it with 7i96_pktd.bit firmware. The following terminal output seems to confirm that.

jim@LinuxCNC:~/linuxcnc/configs/mesa_uart$ halrun
halcmd: loadrt hostmot2
Note: Using POSIX realtime
hm2: loading Mesa HostMot2 driver version 0.15
halcmd: loadrt hm2_eth
hm2_eth: loading Mesa AnyIO HostMot2 ethernet driver version 0.2
halcmd: loadrt mesa_uart names=hm2_7i96.0.uart.0
hm2: Can not find UART instance hm2_7i96.0.uart.0.