Create a serial port in the Vectrex address space

[phillipeaton]

A serial port connected to a terminal emulator on a PC is handy for debugging and allows interactive environments like Forth or BASIC to run.

I'd like a serial port to run something similar to my serial port handler that works on a VecFever (code below is in Forth):

HEX

\ VecFever UART serial port interface. VecFever provides buffering (256 bytes each way?)
7FFB EQU v4eTxStatReg \ Read, negative if transmit buffer is in use, positive otherwise
7FFB EQU v4eTxByteReg \ Write
7FFC EQU v4eRxStatReg \ Read, zero if no data received, otherwise != 0
7FFD EQU v4eRxByteReg \ Read, upon reading, 7FFC is automatically cleared
7FFE EQU v4eLEDReg \ LED Register, probably read/write?

CODE KEY? \ -- f return true if char waiting
6 # ( D) PSHS, CLRA, v4eRxStatReg LDB,
NE IF, -1 # LDB, THEN, NEXT ;C

CODE KEY \ -- c get char from serial port
6 # ( D) PSHS, BEGIN, v4eRxStatReg LDB, NE UNTIL,
v4eRxByteReg LDB, CLRA, NEXT ;C

CODE EMIT \ c -- output character to serial port
BEGIN, v4eTxStatReg LDA, MI UNTIL,
v4eTxByteReg STB, 6 # ( D) PULS, NEXT ;C

Describe alternatives you've considered
Other alternatives are available, but a VEXTREME is cheaper than the other alternatives and/or potentially provides a lot more functionally.

[gtoal]

This - and any other virtual devices added by the vextreme - might be placed in the C000-C7FF space so as not to interfere with the rom space (0000-BFFF). Although I'm not sure why a virtual device interface is better than the existing RPC mechanism for calls to the Vextreme?

[phillipeaton]

All I know about RPC is that it can mean Remote Procedure Call. How would I use that in place of a serial terminal? Can you point me to the code?

…

On Fri, 17 Apr 2020, 18:17 Graham Toal, ***@***.***> wrote: This - and any other virtual devices added by the vextreme - might be placed in the C000-C7FF space so as not to interfere with the rom space (0000-BFFF). Although I'm not sure why a virtual device interface is better than the existing RPC mechanism for calls to the Vextreme? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#50 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKRZ2LT7VX54I2TR2KDN5LLRNB6KHANCNFSM4MIXR4MA> .

[gtoal]

All I know about RPC is that it can mean Remote Procedure Call. How would I use that in place of a serial terminal? Can you point me to the code?
…

It's not in place of a serial terminal - it's in place of a memory mapped device register.

here's the led test which sends commands to the vextreme arm by rpc - look for rpcfn near the end of the file:
https://github.com/technobly/vextreme/blob/master/code/led/led-test1/led-test1.asm

the implemented calls are in doHandleEvent, in
https://github.com/technobly/VEXTREME/blob/master/code/stm32/main.c#L527

I would suggest adding serial get/put/test in there... maybe also have it support an interrupt-driven buffer?

Interestingly, it appears your request is already half implemented!

// Writes to 0x0000 will have the data byte immediately forwarded to the serial TX pin for debugging
// ------------------------------------------------------------------------
// Is it a write to addr #$0000 = serial port addr
// TODO: avoid addr 0 because Polar Rescue writes there occassionally