Previously, the TX pin would be set to output first and then written high (assuming non-inverted logic). When the pin was previously configured for input without pullup (which is normal reset state), this results in driving the pin low for a short when initializing. This could accidenttally be seen as a stop bit by the receiving side. By first writing HIGH and then setting the mode to OUTPUT, the pin will have its pullup enabled for a short while, which is harmless. |
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bootloaders | ||
cores/arduino | ||
firmwares | ||
libraries | ||
variants | ||
boards.txt | ||
platform.txt | ||
programmers.txt |