I have found myself on several occasions away from a PC but needing a small serial Terminal / monitor to view the start-up diagnostics of one of my projects; the traditional boot-up health check. It is routine for me, after the main project is constructed and working, to add a little diagnostic code which uses the on board serial interface of Atmel chips such as the Atmega328P found in Uno, Mini, Mini Pro. Also, this is applicable to the Nano, Teensy, and 32u4 products from Adafruit and Sparkfun. If your project can afford the overhead of the extra code and the light demands of the serial output on the internal UART, then there is little concern for using the serial output.
I constructed this project from Chinese parts which totaled:
Mini Pro 328: ... $2.88 ea (delivered in Qty 5)
Nokia 5110: ....$2.61 ea (delivered in Qty 5)
Total cost for 5 units including shipping: $27.41Price each: ... $5.48
I will give equivalent links to U.S. power houses that stock similar items and stand-by-them with support and replacement guarantees:
Adafruit: $10.00Nokia 5110: http://www.adafruit.com/products/338 Sparkfun: $9.95Pro Mini 328 3.3V: https://www.sparkfun.com/products/11114
To test my portable 3V self-contained serial 9600 BAUD terminal, I connected 2 AAA batteries and a 3.3V GPS with 9600 BAUD output. The success is seen in the lead-in picture and the YouTube video to the right.
The code is simple and you can extend it. It only manages newlines and carriage returns at the moment along with numerals and upper/lower case. But it is a hack... and happily, it is totally open source and hack-able by you.
Text-based electrical connections are listed in the Defines.h file of the ZIP, but the connections are identical to the Nokia display in my project: http://www.hackster.io/rayburne/magic-morse-on-arduino so you can use the Fritzing diagrams there if you prefer.
A 3 Volt Arduino allows for direct connection to 3 Volt devices such as the GPS I used as an example and it makes driving the 3V Nokia display a breeze.
But, if your serial line is 5 Volts, you will need to down convert the logic level to use on your 3V mini-terminal. There are many considerations and the topic is too convoluted (too many opinions) for me to explain everything here. So, educate yourself and select something appropriate for what you intend on doing:
One of the biggest PITA about the Nokia 5110 is that every one seems to have a different contrast requirements. This essentially is just a line in the code that sets a register in the Nokia controller... but, unless you set this correctly, you may have no display to full dark display and it is ambient temperature sensitive.
So, I hacked a simple routine to allow you cycle through all of the possibilities and then when things look the best to you, pull the jumper and the value is written to EEPROM and used afterwards. If you plan on taking this out and about where temperatures will vary this becomes a requirement.
To calibrate your display, power the unit off, connect a jumper from Gnd to Arduino Pin D8 and power on the unit. Allow it to cycle once or twice for you to get an idea of what the best display value will provide. Then as the display cycles around again, just pull the wire on Pin D8 when the display looks the best. The value is written to EEPROM and the program restarts and uses that value.
You may wish to consider using this routine in all of your Nokia 5110 projects! You may also wish to connect a small push button switch (like Reset) so that you can use a small stylus and set this anytime you desire.