Connector Pinout Reference
Pinouts for USB-A/B/C, HDMI, RJ45, DB9, JTAG/SWD, Raspberry Pi GPIO, Arduino and ESP32 — diagrammed and searchable.
Example: Raspberry Pi 40-pin GPIO header: The 40-pin header common to every Raspberry Pi since the B+, including Pi 5. Odd pins are the inner row when the header is at the top of the board.
Check it against real silicon
Chiprun runs your firmware on an emulated microcontroller and hands back the UART output, so you can confirm these numbers rather than trusting them.
Frequently asked questions
What are the Raspberry Pi GPIO pin numbers?
There are two numbering schemes and they do not match. Physical (or BOARD) numbering counts pins 1–40 along the header. BCM numbering refers to the SoC's GPIO lines, so physical pin 7 is BCM GPIO4. Most libraries default to BCM, which is what the table above shows.
Are Raspberry Pi GPIO pins 5 V tolerant?
No. They are 3.3 V and connecting a 5 V signal directly can damage the SoC. Use a level shifter, or a divider for input-only signals. The 5 V pins on the header are power output, not I/O.
Why does my USB-C cable charge nothing?
Missing CC resistors. A USB-C sink has to advertise itself with 5.1 kΩ from each CC pin to ground; without them, a compliant source never turns on VBUS. Cheap adapters that omit these work on old chargers and fail on good ones.
What is the difference between T568A and T568B?
Only the orange and green pairs are swapped. Either works as long as both ends of a cable use the same one. A cable with A on one end and B on the other is a crossover — rarely needed now that equipment has Auto-MDIX.
Why does my SWD debugger say no target detected?
Most often VTref is not connected. It is not a supply — the debugger uses it to sense the target's I/O voltage, and without it the probe cannot set its levels. After that, check that the target is actually powered and that nRESET is wired.
Related tools
Logic Level Reference
Input and output thresholds for TTL, CMOS, LVCMOS and LVDS, and which families you can safely interconnect.
Reference
Microcontroller Comparison Table
Filterable comparison of common microcontrollers by core, clock, flash, RAM and peripherals — with which ones you can emulate in Chiprun.
Reference
I²C Pull-Up Resistor Calculator
Minimum and maximum pull-up values from bus capacitance and rise-time limits, per the I²C specification.
Firmware
UART Baud Rate Error Calculator
Register value and percentage error for any MCU clock and baud rate, with a verdict on whether the link will actually be reliable.
Firmware
555 Timer Calculator
Design astable, monostable and 50%-duty 555 circuits. Get the schematic, the waveform, and a bill of materials in stock E24 values.
Circuits
Battery Life Calculator
Runtime from capacity and load — including a duty-cycled sleep profile for battery-powered IoT nodes that spend most of their life asleep.
Power & Wiring