Issues with serial port on Win9x hosts

[giulioz]

While the JS->Win communication works without any problem, sending things from the guest to the hosts works only on the first call.

If I set an event handler on the JS side with emulator.add_listener("serial0-output-char", console.log); and I try sending multiple data from the windows side (using WriteFile(hComm, data, length, &written, NULL);), only the data of the first WriteFile gets received. I've tried multiple combinations of stop bits, baud rate, timeouts, flow control. In QEMU, instead, it works fine.

This can be further reproduced with the Windows 98 example, using HyperTerminal (http://copy.sh/v86/?profile=windows98):

The first letter wrote using HyperTerminal is received in the serial console, while all the other ones are not. Communicating from the host to the guest, though, works perfectly.

Any pointer? Thanks!

[giulioz]

For further info, this is the configuration being used with HyperTerminal:

[giulioz]

Even easier way to reproduce: http://copy.sh/v86/?profile=windows31
Program Manager > Accessories > Terminal > COM1 > Write something in the terminal

[giulioz]

Update: apparently, after each data receive the ints property of UART0 is set from 4 to 0.
Setting it to 4 using emulator.v86.cpu.devices.uart0.ThrowInterrupt(2) fixes the problem and enables receiving another chunk. Seems a bit hacky though, I need to do this every time I use a WriteFile from the windows side.

[giulioz]

Update 2: calling ThrowInterrupt manually doesn't always fixes the problem, but commenting this line does:
https://github.com/copy/v86/blob/master/src/uart.js#L174

[copy]

I can reproduce this issue. Unfortunately, I don't know a proper fix. The code is shared with jor1k: https://github.com/s-macke/jor1k/blob/e07dbe1/js/worker/dev/uart.js#L215