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42 votes

What were the applications of 5/6-bit serial port formats?

Five-bit teletypewriter codes ("Baudot", etc.) As far back as the early 1900s (believe it or not) there were teletypewriters. They were intended to replace Morse-style telegraphy, directly printing ...
26 votes
Accepted

How does Laplink achieve "high speeds" on standard/legacy serial ports?

It's not dark magic, it's just that there is no hardware limit for 9600 bps to begin with. There are many factors at play here, it's just not about the UART chip. The speed depends on basically from ...
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23 votes

How to transfer file(s) between modern Linux host and HP48 handheld calculator?

Prepare hardware Gather hardware Get or make a serial cable from HP48 to DB9 (most common) or DB25 (instructions on https://www.hpcalc.org/hp48/docs/faq/48faq-12.html, the core of it being: looking ...
22 votes

Why do articles use the term "UART" instead of "serial port"?

Simply, a UART is a serial port, but a serial port is not necessarily a UART. Serial port is a general term for anything serial, without further specification, while a UART defines a transceiver for a ...
  • 184k
22 votes

How does Laplink achieve "high speeds" on standard/legacy serial ports?

A tight polling loop can easily achieve a solid transfer speed of 11,520 bytes/second over a 115,200 baud serial link, even when using a moderately slow processor. Even if a processor can only run ...
  • 31.1k
20 votes

Why are symmetric bi-directional communication port cables not always crossover cables?

RS-232 is a special case. The original purpose of RS-232 was to connect a computer or computer terminal (a.k.a., "Data Terminal Equipment" or "DTE") to a modem (a.k.a., "Data ...
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19 votes
Accepted

Will any serial mouse connect to Classic Macs?

The pre-ADB Macintoshes use a simple quadrature-encoded mouse input, no formal serial protocol. Quadrature encoding is a simple, physical process, that lends itself to a convenient cheat if you're ...
  • 32.9k
18 votes
Accepted

9-pin vs 10-pin serial port ribbon cables

In more recent designs, since the mid-2000s I think, it became common to include "key" pins like this to reduce assembly errors. In most cases the pin removed was non-essential in the first ...
  • 16.2k
17 votes

Is it possible to just construct a simple cable serial↔︎serial and send data from PC to C64?

The C64 does not have a real standard RS-232 port. (The C64 port marked Serial is something quite different, namely its native IEC port.) The User Port, however - apart from being usable as a a ...
  • 4,368
16 votes

What were the applications of 5/6-bit serial port formats?

The Baudot code uses 5 bits, and IIRC at least one of the mechanical teleprinters needed 1.5 stop bits to provide the time for the mechanism to do its thing, this at 45 baud. RTTY radio comms is ...
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15 votes
Accepted

Where is/was the standard V.35 connector defined?

This is the Winchester connector. The form factor is specified in ISO 2593. ISO standards are typically not available for free, which may be why you had trouble finding information on it. I'm not ...
14 votes

Why are symmetric bi-directional communication port cables not always crossover cables?

Answering this for all kinds of connections is simply way too broad. But there are three basic facts: Connected devices have specific functions. Connecting devices of the same function is an ...
  • 184k
14 votes
Accepted

How can I connect a Psion Series 5 PDA to a 64-bit Windows PC?

Hardware It is possible to connect the RS232 serial cable with a current Windows PC using a compatible RS232-USB adapter. I have a 'Belkin PDA Adaptor', which works well and has 64-bit drivers for ...
13 votes

Creating a 'bridge' between a serial port and a Telnet session in Windows 98?

In DOS, I remember being able to start COMMAND.COM on a COM port simply by doing this: REM Set COM1 speed and settings MODE COM1:38400,N,8,1 REM Hand over control to COM1! COMMAND COM1 REM The ...
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13 votes

What were the applications of 5/6-bit serial port formats?

Traditional Teletypes and many paper tape storage systems use these. You won't be able to read reels of punched paper tape if you drop support for 5 bit data. Nor will you be able to interface with ...
13 votes

How can I read COM port addresses from BIOS in QuickBasic 4.5?

The BIOS list only contains addresses of up to four standard 8250-type COM ports found at boot at the standard addresses. It will not contain more than four ports, it will not contain any non-8250 ...
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13 votes
Accepted

How can I read COM port addresses from BIOS in QuickBasic 4.5?

Well, this is to be expected; the BIOS Data Area has only four slots for I/O addresses of serial ports, with slots for parallel ports immediately following. In the MEMORY.LST file from Ralf Brown’s, ...
  • 18.7k
12 votes

Serial Receipt Printer Garbage

Looks like inverse polarity. The CR code is 015, 00001101 in binary. The codes for "=" and "y" are 075 and 171, 00111101 and 01111001 respectively. Note the sequence of four zeros in CR, and ...
  • 16.8k
12 votes
Accepted

Reverse engineering an RS-422 protocol with access to only one device?

I posted a comment on the reverse-engineering Q&A you linked before I realized it'd do better as an answer here. The answerer there found that googling Accom and Axial from your photo turns up a ...
  • 5,333
12 votes
Accepted

Did any equipment ship with odd serial parity by default?

Just one example: The Trimble GPS receiver's (used on agricultural positioning systems, for example) proprietary TSIP protocol (roughly end of the century, so somewhat retro already) uses odd parity ...
  • 29.1k
11 votes
Accepted

Transfer files to DOS over serial cable from Linux?

Some sort of comms program that supports Zmodem on the 286 end and use "sz" to send from the unix end. Zmodem has some advantages in that usually the receiving computer will auto start reception of a ...
  • 5,165
11 votes

Connecting Panasonic "Penwriter" RK-P400C to modern PC using USB to serial cable

I successfully got the RK-P400C printing from a serial console (minicom on Linux) today. Here's how to do it for future reference...;) The DB25 connector on the right side is a 25 pin serial port. At ...
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11 votes
Accepted

Is there an obstruction to emulating Gameboy link cable over Wi-Fi?

Cariad Keigher's Adventures with an 11,000 kilometre-long Game Boy Advance link goes into detail on how timing-sensitive the protocol is to establish context for a story about emulating both sides of ...
  • 5,333
10 votes

Transfer files to DOS over serial cable from Linux?

You can also use dosbox or dosemu to run a simulated DOS environment, give it access to whatever ttyS* or ttyUSB* you have, and then use the DOS-to-DOS transfer methods. Personally, I prefer Laplink, ...
  • 22.9k
10 votes
Accepted

How can I send RS-232 serial data to a Tandy plotter reliably?

The manual says nothing more than it can print 12 characters per second and it uses BUSY pin. Even if you have connected BUSY output to CTS input, and turned RTS/CTS handshaking on, there is still a ...
  • 21.6k
10 votes

9-pin vs 10-pin serial port ribbon cables

In addition to the fact that some serial-port adapter cables have a blocked off pin, I've seen boards and cards use two different pinouts. On a DB-9 male, the pins are numbered 1 2 3 4 5 6 ...
  • 31.1k
9 votes

How was parity used with modems?

By the time I got my first analog modem, around 1980, my experience was the same as yours. Even and odd parity on 7-bit data was available, but almost all the BBSs featured 8N1. (The modems even still ...
  • 8,223
9 votes

What were the applications of 5/6-bit serial port formats?

It would be useful to establish whether anyone knows of any application for these which is still in service. RTTY (FSK modem over radio) still uses 5 bit code at low bitrates 45/50. It's often still ...
  • 91
9 votes

Transfer files to DOS over serial cable from Linux?

This has already been well answered, but I wanted to respond with a couple of bootstrap solutions: that is, if all you have is a Linux box connected to a DOS box via a null-modem cable. minicom on ...
  • 18.1k

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