ATtiny84/85 Transmit Only Serial Output

This instructable corrects/updates/amends a previous instructable which used the SoftwareSerial class to implement serial output for the Atmel ATtiny84 and ATtiny85 devices. There are a couple of significant issues associated with use of the SoftwareSerial class:
It requires use of 2 pins, 1 for transmit and 1 for receive, even though serial output requires only transmit It uses a Pin Change interrupt for receive, therefore tying up a device Port. In fact, it allocates ALL the device ports to the receive pin change ISR.Fortunately, Nick Gammon modified the SoftwareSerial class to create a transmit only version, SendOnlySoftwareSerial, which requires only 1 device pin and no interrupts. This instructable follows the steps of the previous SoftwareSerial instructable pointing out the differences in use of the SendOnlySoftwareSerial class for serial output. Differences are highlighted in red; the original instructable is referenced where text/procedures are the same.”

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