Calculators that get the byte order right
Modbus frames, CRC polynomials, register decoding, and the resistor and RC values around the board — the fiddly parts of firmware and electronics work, answered with parts you can actually buy. No login, no install; everything runs in your browser and nothing you paste leaves your machine.
Modbus
Build, decode, and sanity-check RTU traffic without wiring up a gateway.
Modbus CRC16 Calculator
CRC-16/MODBUS for any hex payload, with the wire byte order spelled out.
Modbus RTU Frame Builder & Parser
Decode captured frames field by field, or build a request from scratch.
Modbus TCP Frame Builder & Parser
MBAP headers decoded, the length field checked, and a capture split into frames.
Modbus Register Decoder
Register pairs to float32/int32 across every byte order devices use in practice.
CRC & Checksums
Every common polynomial, plus custom parameters when a datasheet disagrees with the catalog.
Conversion
Move between hex, binary, floating point, and the byte orders real devices use.
IEEE 754 Float Converter
Flip bits directly and see the exact value a float really holds, not the rounded print.
Hex / Binary / Decimal / ASCII Converter
Fixed-width conversion with signed readings, byte order, and clickable bits.
I²C Address Converter
7-bit to 8-bit both ways, reserved ranges, and what a scan result probably is.
Intel HEX Parser
Record-by-record validation plus the memory map the file really produces.
Motorola S-Record Parser
SREC files record by record, with the checksum and terminator mismatches called out.
Fixed-Point Q Format Converter
Q format conversion with the exact stored value and both naming conventions.
C Struct Padding Visualizer
Byte-level layout, padding holes, and a reordering that shrinks the struct.
Timing & Bus Config
Work out divisors, prescalers, and the error margins that decide whether a link is reliable.
UART Baud Rate Error Calculator
Divisor, error margin, and register values — plus the clocks that divide exactly.
Timer Prescaler & Period Calculator
Prescaler and reload splits ranked by PWM resolution, with the register values.
CAN Bit Timing Calculator
Segments, sample point, and register values for classic CAN and CAN FD.
J1939 PGN Decoder
Identifier to PGN and back, with the PDU1 destination kept out of the PGN where it belongs.
CAN Filter and Mask Calculator
Which IDs a filter really admits, and the tightest filter for a list — with the false accepts counted.
Electronics
Circuit values snapped to parts you can actually buy, with the error that snapping costs.
I²C Pull-Up Resistor Calculator
The window between pulling low and rising in time, with the standard values inside it.
NTC Thermistor Calculator
ADC counts to temperature, with the resolution and self-heating the divider decides.
Ohm's Law Calculator
Any two of V, I, R and P give the other two, and it shows its working.
Parallel & Series Resistor Calculator
Totals both ways, plus the E-series pair that lands on a value you cannot buy.
Voltage Divider Calculator
Real E-series resistor pairs with the error and tolerance band, not just a ratio.
LED Series Resistor Calculator
Standard values either side of the ideal, the current each really gives, and the rating it needs.
Resistor Color Code Calculator
Colours to value and back, with a check that the value is one anybody actually makes.
RC Time Constant & Filter Calculator
Real R and C pairs for a cutoff, with the tolerance band, step response, and ADC settling time.
PCB Trace Width Calculator
IPC-2221 width for a current and rise, the fab widths either side, and the drop the trace adds.
Battery Life Calculator
Life from a duty-cycled current profile, with where the charge goes and whether a coin cell can take the pulse.