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I have always assumed that computer keyboards do not, in the typical case, contain integrated circuits. And also, now that I think about it, there must be a set of standard electrical (digital?) signals defined by key that a keyboard sends.

I understand that some fancy keyboards may have their own macro capabilities supported by ICs, but basic keyboards don't use ICs, or?

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  • \$\begingroup\$ Yes they have ASIC’s or std IC’s to convert N-Key rollover Matrix scans into serial data. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 19 '19 at 14:07
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    \$\begingroup\$ To get those standard electrical signals you need to squeeze 100+ different keys into just a few electrical wires. That takes a lot of circuitry even if it's not USB (and USB is really, really complicated so you absolutely need an IC there). Keyboards are cheap, heavily mass produced products so why wouldn't they invest in an IC to save money per keyboard in the long run? \$\endgroup\$ – DKNguyen Jun 19 '19 at 14:15
  • \$\begingroup\$ Thank you to all responders. As several of you suggested, I hadn't thought through this question deeply enough before I came to my assumption. You have helped me to understand this much more clearly \$\endgroup\$ – ControlAltDel Jun 19 '19 at 14:20
  • \$\begingroup\$ A wire-less keyboard certainly needs internal IC + battery. A keyboard connected with just a few wires inside a small-diameter cable requires an internal IC to serialize key-presses. But it is possible to construct a keyboard having no internal ICs. The cable connected to the computer (where the matrix is scanned) would have many wires - users would find awkward and not ergonomic. As for cost, the IC inside the keyboard that scans the key matrix is the cheaper ubiquitous solution. \$\endgroup\$ – glen_geek Jun 19 '19 at 15:14
  • \$\begingroup\$ Ctl-Alt-Del. Try n Key rollover with fast typing. all keyboards have a 🕷. after 2 or 3 keys it is not the next key that is sent but the 1st one released so 2 letters often get reversed not due to order pressed but faster release when above condition occurs \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 19 '19 at 18:08
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Even the earliest mainframe computer keyboards had circuity! Keyboards buttons are usually placed in an X-Y matrix such that any inputs need to be converted to some serial code (scancodes or keycodes) and sent to the computer. The matrix reduces the number of individual buttons to scan which in a keyboard, saves a lot on wiring and processing power. The scanning procedure typically involves iterating through every combination of rows and columns to check if button press:

Keyboard scanning matrix

The use of the matrix created several well known problems such as rollover. When multiple keys are held down simultaneously, this circuit is unable to register all the inputs. Modifications in the both the layout of the keys and software of the microelectronic later improved these conditions.

Also, if you might have heard of the connection types PS/2 or USB (and of course the AT Connector) which send serial communication through these ports. These standards regulate the communication protocol between the keyboard the computer, necessitating the microcontroller.

Image Source: https://en.wikipedia.org/wiki/Computer_keyboard#/media/File:FunctionalCircuitDiagramOfKeyboardNumPadScanningProcedure-small.gif

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Do Computer keyboards have ICs?

Short answer. YES

You CANNOT have a PC keyboard without IC's (and they ALL have microcomputers as at least one of the ICs in the keyboard).
The PC keyboard has a serial protocol of events sent to the computer it's attached to. The serial protocol has little to do with scanning the matrix of keys on the keyboard, which is only a sub task of those required by the keyboard controller. The computer expects in the serial protocol to be advised about keydown/keyup events so that the status of keys may be maintained. Read this document to get an idea of what is going on.

Nothing is simple.

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Yes.

Most keyboards arrange the keys into a matrix to reduce the number of signal lines connected to the keys, but that still leaves an inconviniently large number of signals to route over the cable from the keboard to the main system board. For example a PC keyboard has about 21 columns and 6 rows (though not all positions are used) so to wire up the keyboard matrix directly would require about 27 wires. Therefore all full size keyboards i've seen (small keypads are a different matter) contain some form of active circuitry to reduce the amount of wiring.

Historically different computers handled the keyboard differently, The BBC micro keyboard for example contained multiplexer and demultiplexer chips to reduce the number of signal lines, but left the active scanning process to the main processor.

IBM PCs and compatibles on the other hand have the scanning of the matrix handled in the keyboard itself. The keyboard uses the results from the scans to generate key down and key up events which are sent over USB or PS/2 to the computer.

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but basic keyboards don't use ICs, or?

What makes you come to that conclusion?

Modern keyboards use USB, in order to communicate with a PC over USB some protocol has to followed. Implementing this protocol without using any IC would make for a very large and expensive and power hungry keyboard.

When the keyboard is communicating with the PC it sends codes. Also making these codes without ICs is theoretically possible but your keyboard would require a humming box next to it similar in size to a refrigerator, it would consume a lot of power and it would be expensive.

In an IC we can integrate all the functions above for a few $$ or less.

I challenge you to find a computer keyboard that does not have any IC inside. My bet: you will be unable to find one.

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  • \$\begingroup\$ My 1st calculator was a computer and I interfaced to it directly with CMOS analog switches to make a digital 1” 4 digit LED counter of any value. Steps, calories count up or down ...circa 1976. “5000” “=“ “-1” “=“ “=“ “=“. For a stairclimber exercise machine on the “cheap”. (Free invention) \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 19 '19 at 14:16
  • \$\begingroup\$ The failed keyboard I pulled out of an Asus eePC a while back didn't have any ICs on it. That's because the keyboard module was just a load of buttons connected to two ribbon cables. Of course, the controller must have been soldered to the motherboard. \$\endgroup\$ – Simon B Jun 19 '19 at 14:23
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Yes, of course keyboards have ICs.

Think about it. On one hand, you have several dozen switches. On the other, you have a serial data stream representing the closing and opening of those switches. How do you propose getting from one to the other without ICs?

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  • \$\begingroup\$ Maybe with semaphore smoke signals? Like the American Indians did. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 19 '19 at 14:17
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The only keyboard in my experience which didn't use ICs would be that of a Teletype, which used motors, gears, cams and switches to send serial data to a computer. They were heavy, slow, noisy and required considerable maintenance.

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