Question regarding RS-232 interface for C1P

[MK14HAK]

Awesome.
By the way, the same routine running with the loop J3 2-3 (no connection to other serial device) you can measure those voltages at ACIA-2 . They are just reversed ie Tx lo will Rx lo.

[stm]

I did first tests to upload programs over the serial port. I uploaded a BASIC program via the LOAD command, and a program compiled with cc65 into the machine monitor.

The surprising result is that loading the BASIC program does not work, while the uploading via the machine monitor works reliably. In both cases I sent the binary data of the file from my Windows 10 laptop with Powershell using the System.IO.Ports.SerialPort class over an USB to RS-232 adapter.

The strange thing is that I always get the same errors in the uploaded BASIC program, e.g. always the same line numbers are corrupted so that for example line number 210 is truncated to 10. The rest of the line is ok then.

Do BASIC programs need any special formatting for reliable upload over RS-232?

[dave]

Nice!

Do BASIC programs need any special formatting for reliable upload over RS-232?

Yes, especially when you increase the speed over 300 baud. The C1/2/4 machines don't by default use interrupt driven I/O, so there's no buffering of the serial stream. BASIC has to scroll the screen and digest the line before it's ready for the next one. That takes a few msec. You will need to add some padding at the beginning of each line to soak up those few msec, and the paddiing will increase proportionate to the baud rate.

Try entering some NULLs (0x00 = ^@) at the start of each line.

BASIC actually has a command (NULL x, where x=1 to 8) to add some NULL bytes automatically at the beginning of each line when listing programs to cassette, for exactly that reason.

Dave

[MK14HAK]

A9 03
8D 00 F0
A9 B0
8D 00 F0
60

Will give you 16X your board rate for MC loads.(Reset will return to normal)
Cegmon allows you to set your screen window to 1 line for fast scrolling. Screen Edit of BASIC and Assembler source, breakpoints etc...
Your file transfer program (eg TeraTermPro ) may allow you to set a line delay. 500ms works well for BASIC at 300 baud if your file has no NULLS.

[stm]

Nice!

Do BASIC programs need any special formatting for reliable upload over RS-232?

Yes, especially when you increase the speed over 300 baud. The C1/2/4 machines don't by default use interrupt driven I/O, so there's no buffering of the serial stream. BASIC has to scroll the screen and digest the line before it's ready for the next one. That takes a few msec. You will need to add some padding at the beginning of each line to soak up those few msec, and the paddiing will increase proportionate to the baud rate.

Try entering some NULLs (0x00 = ^@) at the start of each line.

BASIC actually has a command (NULL x, where x=1 to 8) to add some NULL bytes automatically at the beginning of each line when listing programs to cassette, for exactly that reason.

Dave

Ah, the NULL command rings a bell now, thanks. So if I send the program from my laptop from a plain ASCII file, I need to modify my PowerShell script to add the NULL bytes before each line. I will try that next.

[stm]

After adding the feature to send three NULLs before each line, uploading BASIC programs from text files now works perfectly.

[MK14HAK]

Could you show us how you did this in your script please Stephan.

[stm]

Could you show us how you did this in your script please Stephan.

Sure. This is the script that uploads a BASIC file:

Code: Select all

<#
.SYNOPSIS

Upload BASIC file over the RS-232 port to a Challenger 1P

.DESCRIPTION

This script uploads BASIC files over the RS-232 interface of an
Ohio Scientific Challenger 1P. The computer must have been put into
load mode with the LOAD command. The script sends a configurable
number of NULL bytes before each line.

.PARAMETER baudrate

Baud rate of the serial port

.PARAMETER nullbytes

Number of NULL bytes to send before each line

.PARAMETER comport

Windows COM port

.PARAMETER infile

BASIC file to upload

#>

param (
    [string]$baudrate = 300,
    [string]$nullbytes = 3,
    [Parameter(Mandatory=$true)][string]$comport,
    [Parameter(Mandatory=$true)][string]$infile
)

$infilepath = Resolve-Path $infile

$nulls = [Byte[]] (,0 * $nullbytes)

$port = new-Object System.IO.Ports.SerialPort $comport, $baudrate, None, 8, one
$port.NewLine = "`r"
$port.Open()
$reader = [System.IO.File]::OpenText($infilepath)
try {
    for() {
        $line = $reader.ReadLine()
        if ($line -eq $null) { break }

        # Write the NULL bytes before each line
        $port.Write($nulls, 0, $nulls.Count)

        # process the line
        $port.WriteLine($line)

        # echo the line to the shell
        $line
    }
}
finally {
    $reader.Close()
    $port.Close()
}

The script to upload a file into the PROM monitor is simpler:

Code: Select all

<#
.SYNOPSIS

Upload a file over the RS-232 port to a Challenger 1P into the PROM monitor

.DESCRIPTION

This script uploads a file over the RS-232 port into the Challenger 1P
PROM monitor. The file must consist of a sequence of commands and hex digits
that could be typed in in PROM monitor mode.

Example file contents (switch to address mode, enter address 0x200,
switch to data mode, enter bytes A2, FF, 9A, D8):

.0200/A2
FF
9A
D8
<etc.>

.PARAMETER baudrate

Baud rate of the serial port

.PARAMETER comport

Windows COM port

.PARAMETER infile

File to upload

#>

param (
    [string]$baudrate = 300,
    [Parameter(Mandatory=$true)][string]$comport,
    [Parameter(Mandatory=$true)][string]$infile
)

$port = new-Object System.IO.Ports.SerialPort $comport, $baudrate, None, 8, one
$content = [IO.File]::ReadAllBytes($infile)
$port.Open()
$port.Write($content, 0, $content.Count)
$port.Close()

I maintain these scripts here in the GitHub repository where the cc65 example programs for the C1P are versioned.