The arrangement of pins and their functions on a device
Most devices with pins have different functions for different pins. The pin-out maps the function of each pin to the physical pin on the device.
Questions tagged [pinout]
299 questions
56
votes
10 answers
Why is an Ethernet cable not grounded?
There is no dedicated GND in the classical Ethernet 8P8C ("RJ45") pinout.[1]
Why does the Ethernet spec not include a ground, unlike many other cable types used for interconnecting devices that may both have its independent power source as well,…
mykhal
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4 answers
Why do some microcontrollers have a single port's pins distributed widely around the package?
I was trying to use a microcontroller's 16-bit IO port to interface with a parallel display. I found that the IOs of a single port (let's say PORTB) are highly fragmented around the microcontroller:
For example in the image above, PB0~PB2 are…
Tirdad Sadri Nejad
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24
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4 answers
Which of these marks signifies Pin 1 on the STM32F (LQFP64)?
I'm using the STM32F105, in a LQFP64 package. It has two circular markings, on opposing corners of the IC. This picture is for a different ST ARM, but the markings and silkscreen are similar:
The larger mark in the upper-right of the picture has a…
bitsmack
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What's an alternate pin function on a microcontroller?
I'd like to know what "Alternative Function" refers to in the context of the IO ports of a microcontroller.
I don't need to know how to activate it when connecting to a peripherial, but I'd like to know what it exactly is and why we'd need it.
user929404
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7 answers
Is there any definitive I2C pin-out guidance out there? Not looking for a "STANDARD"
EDIT: This has been repeated several times, so putting it on top: Yes, it is well known that there is no "standard" for I2C inter-device connectors, but surely this community can formulate a list of "guidance" points for making such interconnects,…
Anindo Ghosh
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16
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3 answers
Program to draw pinouts (and easily visualize pin's multiplexed functions)
Documenting an electronics project is also an important task if it will be used by someone else other than the hardware designer(s). Right now I need to draw a diagram for a breakout board in order to show what functions are available on each pin.…
rasgo
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2 answers
Why would the VCC/GND pins of an ATtiny26 not be aligned?
In the following pinout diagram for an ATtiny26 microcontroller, a 20-pin IC:
The VCC/AVCC and GND pins aren't aligned. Surely it would be easier for PCB design to connect these by going straight across rather than having to cross (requiring vias,…
JYelton
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votes
3 answers
Standard nomenclature for 2-row connector numbering schemes
Two-row connector blocks are ubiquitous in small-run and hobbyist PCB designs. Pitches of 0.1" or 2mm are the most common, and there are all sorts of options for board-to-board or board-to-wire connectors. The problem is that pin numbering schemes…
andrewtinka
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12
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1 answer
Meaning of control pins: CE, OE, WE
Just understanding some syntax. On my Ram (6116) and Rom (27C64) it has a asserted low CE and OE pins. These I believe are control pins.
I'm assuming to use the RAM for example, chip enable (CE) has to be low. Then Output enable has to be low for…
lecardo
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11
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4 answers
Confused about IN/OUT architecture of z80 chip
I am reading the manual, and it's a bit complex. I can't understand the machine code encoding for the life of me, but that's not my main concern ... my main concern is the address/data buses.
I do not understand the difference between the "address…
user33553
11
votes
3 answers
Why JTAG connectors are available in 10pins/14pins/20pins when JTAG is of 5pins
AFAIK, JTAG is requires 5 pins (Wikipedia article):
TDI (Test Data In)
TDO (Test Data Out)
TCK (Test Clock)
TMS (Test Mode Select)
TRST (Test Reset) optional.
Let's add two more Power supply Pins (Vcc and GND).
If it is of 7 pins then why most…
Swanand
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11
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3 answers
Is Texas Instrument wrong with their pin number on TO-92 package?
The official JEDEC standard to number pins on a TO-92 package is the following:
But in many datasheets from Texas Instruments, this order seem reversed. For example, this is a screenshot from the datasheet for the LM185 :
Link to the full…
Iouraxos
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10
votes
7 answers
Why are the pinouts of LPC21xx all over the place?
I am working as a winter intern at a robotics company. My job is to assist the lead embedded developer in... whatever he wants my assistance in.
About a week back, I was handed a NXP blueboard with LPC2148 on it. Although I loved the more…
Rick_2047
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10
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6 answers
Identifying pin numbers from PCB
I have a PCB with documentation. In the documentation, there is referred to specific pins of several jumpers and connectors. On the PCB however, there isn't a label or so for which pin has what number. I need to figure out which pin has which…
user17592
9
votes
2 answers
Handling "Upside-Down" IC Pinouts on PCB
I printed a board recently and, long story short, the pads aren't laid out correctly for two IC's: a SOIC8 MAX1771 and an 80-pin HV507. I moved all the pads from the top to the bottom layer, but forgot to flip the sides. Thus, along one side of the…
Jack Lynch
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