Embedded Calculators & Part Finder
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💡LED Resistor
⚡Ohm's Law
🚌CAN Bit Timing
🔻Voltage Divider
🔠Glyph Mapper
📦Struct Padding
PWM / Timer
Frequency, period, duty cycle
UART Baud Rate
Error rate, PASS/FAIL check
ADC Resolution
LSB voltage, SNR, dynamic range
Watchdog Timer
STM32 IWDG & WWDG timeouts
I2C Timing
Bus timing & pull-up values
CAN Bus Bit Timing
STM32 bxCAN/FDCAN & MCP2515
SPI Timing
Bit period, frame, throughput
RS-485 Bus
Cable length, termination, bias
LIN Bus Timing
Bit, break, frame time
Modbus RTU Timing
Char & inter-frame gaps
Ring Buffer / DMA
Buffer sizing
Register Map → C
Bitfield struct & macros
CRC → C Code
Lookup table & function
Stepper Motor
Steps/rev, microstep, pulse rate
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I2S Audio Clock
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USB Data Lines
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Bit Field Visualizer
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Q-Format Converter
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Number Base Converter
Dec, Hex, Bin, Oct converter
IEEE 754 Visualizer
32-bit Float & 64-bit Double
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C struct padding & visualizer
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Bytes, baud rate & sample times
Glyph Mapper
7-Segment & Character LCD custom font generator
Crystal Load Cap
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Ohm's Law
V, I, R, P — any 2 → all 4
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Vout, loaded divider, Thevenin
LED Resistor
Series/parallel configs & E24
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LM317 Regulator
Adjustable Vout & R2 solver
Current Divider
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RC Filter
Cutoff frequency, gain & phase
dB Converter
dB, dBm & mW bidirectional
CRC Calculator
CRC-8/16/32, 7 polynomials
Checksum / CRC
XOR, Sum8/16, LRC, CRC
PCB Trace Calc
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Active Filter
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Air-core solenoid (Wheeler)
Battery Life
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Units & RTD sensor temps
Wheatstone Bridge
Bridge Vout & balance
Junction Temp
Thermal Tj & max power
Modbus RTU Timing Calculator
Character time and 1.5 / 3.5-character inter-frame gaps for Modbus RTU.
Input
ℹ One character = 11 bits. Above 19200 baud the spec fixes 750 µs / 1.75 ms.
Results
Character Time—
Inter-char (t1.5)—
Inter-frame (t3.5)—
💡 Usage & Formula
char = 11/baud; t1.5 = 1.5·char, t3.5 = 3.5·char (fixed 750 µs / 1.75 ms above 19200 baud).
When you need it: Computing the 3.5-character inter-frame silence and the per-transaction time so you can set a realistic master poll rate and response timeout on a Modbus RTU line.
Worked example: At 9600 bps, 8N1 is 11 bits/char → 1 char = 11 / 9600 = 1.146 ms. The frame gaps are t3.5 = 3.5 × 1.146 = 4.01 ms silence between frames and t1.5 = 1.72 ms intra-frame. Reading 10 registers (~8-byte request, ~25-byte reply) totals roughly 38 ms plus the silences.
Tips & gotchas:
- Above 19200 bps the spec fixes the gaps at
t3.5 = 1.75 msandt1.5 = 750 µsinstead of scaling with baud. - Set the master's response timeout well above the slowest slave's turnaround, or you'll log false timeouts under load.
- RTU relies on exact byte framing — any gap longer than t1.5 mid-frame is treated as a frame boundary and corrupts the message.
- Use Modbus ASCII only where character gaps can't be guaranteed; it doubles the bytes on the wire.
📖 References:Modbus (Wikipedia)