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Serial Baud Rate T-Shirt
“⸮⸮⸮ = Wrong Baud.”
A nerdy electronics tee: the standard serial baud rates, their timing error on a 16 MHz ATmega328P, the receiver's tolerance, and what ⸮⸮⸮ in a serial monitor means.
from $27
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On the shirt
What it teaches
- Serial has no clock wire, so both ends must agree on the baud rate. When they don't, bytes still arrive but decode as garbage.
- ⸮ marks a byte that isn't valid text. The Arduino IDE shows it from 1.8.2 in the 1.x line; IDE 2 shows � instead. The usual suspect is a baud mismatch.
- At 16 MHz the ATmega328P hits 9600, 19200 and 38400 within 0.2 %. On the standard Arduino core, 57600 and 115200 both run about 2.1 % off.
- An 8N1 receiver tolerates about +4.58 / −4.54 % in total, so keep each end within ±2 %.
- An HC-05 module answers AT commands at 38400 only if KEY is held high while it powers up.
Sources
Where every fact comes from
The shirt
Fabric, fit and printing
Bella+Canvas 3001 unisex tee: combed and ring-spun cotton (heather colours are a cotton/poly blend), printed direct-to-garment and made to order. Care: wash cold, inside out; tumble dry low; don't iron the print.