ArduinoISP and Serial RX, TX communication combined

Other Hardware 3rd Party Boards
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ArduinoISP combined with a software Serial RX TX module

I am looking for a software (reliable and well documented) that once uploaded into Arduino Uno transforms the board in both an ISP programmer (like ArduinoISP) and a serial relay that transmits data between a Serial Monitor installed on the Laptop and the target avr.

I would like two of Ardunion Uno's ISP lines to act also as RX, TX when Arduino Uno receives a command from the Serial Monitor to change its behavior from an ISP programmer to a Serial Relay. There should also be an opposite command that will turn back Arduino Uno into an ISP programmer.

Computer running avrdude and Serial Monitor --->>--- USB cable --->>--- Arduino Uno [SS, MOSI (RX), MISO (TX), SCK] --->>--- 4 wires ISP --->>--- [Reset, MOSI (TX), MISO (RX), SCK] target AVR

Reason I need such a hybrid ISP/serial rx, tx
I use avrdude, in conjunction with Arduino Uno loaded with ArduinoISP, to flash various AVRs mounted on breadboards. My target AVRs are programmed with code that transmits / receives data on software Serial tx, rx. I am running out of pins and I do not want to use more than 4 connections for both serial and ISP data links. Also I do not like to change wiring configuration between programming the target AVR and talking on softwareSerial with it.

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Read from this post forward...

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[quote author=Coding Badly link=topic=131047.msg985596#msg985596 date=1352227412]
Read from this post forward... SoftwareSerial with ATTiny84 using ATtiny library - #20 by Coding_Badly - Microcontrollers - Arduino Forum
I have already read the topic. That TinyISP can be what I need but it is not well documented, it is mixed with a communication channel /protocol called Knock Bang ( GitHub - Coding-Badly/TinyISP: ArduinoISP replacement with: Tiny Debug Knock Bang, Monitor, Tiny Tuner 2, and other amenities ) which I do not really need. Also, few users reported success in using your ISP Programmer / Serial Relay and from the dialogs you had with forum members it looked like you corrected errors as you instructed people how to use the code. Also, searching for TinyISP on the net to get more information I fond an entity called USB TinyISP that seems to be a different thing. The name misleads.

Your TinyISP software needs a good Tutorial (like this one) for using it as: (1) ISP Programmer, (2) Serial Relay Tx, Rx, (3) Knock Bang protocol.

You have worked a lot at that TinyISP, which could be of great value, but forget the most important step, a good help page for it. Honestly, you code is like buried somewhere. There is no evidence that more than 10 people have ever tried to use it.