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 ...
- 1,451
31
votes
Accepted
What is the serial protocol commonly used over RS-232 (among other links) and where did it come from?
The bit-serial protocol that is most often used to transfer data frames over RS-232 interface is simply called the "asynchronous start-stop protocol", a method that was patented already in ...
- 35.6k
27
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 ...
- 35.6k
25
votes
Why did Linux standardise on RTS/CTS flow control for serial ports
In short, Linux is a Unix-like operating system kernel and does things like other Unix-like operating systems. The least common denominator for different Unix-like systems is the POSIX standard, which,...
- 35.6k
24
votes
Accepted
Did a serial port card reader sink the prospects of consumer chip card readers?
I have some doubts regarding this story.
First, quite the opposite of what's claimed, one of the advantages of serial-port devices is that using them does not need any deep OS changes. Every OS at the ...
- 499
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 ...
- 231k
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 ...
- 38k
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 ...
- 2,101
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 ...
- 37.9k
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 ...
- 16.9k
18
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 ...
- 4,009
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 ...
- 481
16
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 ...
- 276
15
votes
Accepted
How to read data from Philips P2000C over its serial port to a modern computer?
Most likely you need what's called a null-modem cable with two female 9-pin connectors, that connects pin 5 of one connector (call it X) to pin 5 of the other connector (Y), pin 2 of X to pin 3 of Y, ...
- 38k
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 ...
- 231k
14
votes
What is the serial protocol commonly used over RS-232 (among other links) and where did it come from?
The framing protocol of 'start bit, data bits, stop bits' predates RS-232 and other voltage-based physical encodings. It was used, for example, on 20 mA current loop Teletype interfaces.
It is ...
- 36.9k
14
votes
How to read data from Philips P2000C over its serial port to a modern computer?
The problem is that the Philips computer has a non-standard connector gender. The computer is wired as a 25-pin DTE regarding the signal pinout, but does not use a connected intended for DTEs but a ...
- 35.6k
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 ...
- 1,365
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 ...
- 650
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 ...
- 35.6k
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, ...
- 23.3k
13
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 ...
- 36.4k
13
votes
Why did Linux standardise on RTS/CTS flow control for serial ports
Linux started as a hobbyist operating system. It was in no position to set any kind of standard. Instead, Linux implemented what hobbyists needed at that time. When Linux got popular, the convention ...
- 8,041
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 ...
- 20.6k
12
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 ...
- 21.9k
12
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 ...
- 351
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 ...
- 7,133
Only top scored, non community-wiki answers of a minimum length are eligible