BT Multi Monitor

PLEASE NOTE: Requires additional hardware!
This app is only interesting for those who can program a microcontroller with ADC and serial Bluetooth module (e.g. RN-42).

This app reads a value via Bluetooth. This can be a voltage, a temperature, a pressure or whatever. This value can be displayed, observed and recorded.

The observation method is similar to a traffic light. It makes the colors green, yellow and red from specific value ranges (and similar to a traffic light, green means "OK", red means "ALERT", and yellow is the transition state).

You can adjust the ranges for "Green" and "Yellow", depending on your requirements. Tests are as follows: Value within green range? Display shows green. Else, value within yellow range? Display shows yellow. Else, display shows red and - if enabled - an alarm is triggered.

Also adjustable is the response time so that a value change does not lead to a color change immediately. Only a certain duration of value changes lead to color changes. This prevents single peaks from triggering color flicker.

"Red" can trigger an alarm using a siren (plus vibration), using Text to Speech with text you can edit in settings, or by playing an audio file from SD Card. You can set a fixed volume, or use the media volume.

Rotating the display starts a special display mode, which is configured in settings: You can multiply the "raw" value by a factor and you can add an offset. The number of decimal places as well as the digit size are adjustable. Finally, you can add a unit (e.g. "Volt") and toggle min/max display. Optionally, the displayed value can be read out at regular intervals.

A click on the display shows some statistics.

There is also a log-file option with the possibility to visualize the recorded data as diagram (when the display is rotated).

The maximun recording time is 10 hours. The log file (log.csv) is located in the directory "BT Multi Monitor" on the SD Card and is overwritten each time the app is started. As an alternative, several log files (date-time.csv) are also possible.

In addition log files can be processed by programs like "Excel&Co".

Bluetooth device selection: The selection can be limited to device names containing a particular string, defined in settings. If only one device is available, it is selected automatically.

Technical info

- Bluetooth profile: SPP (Serial Port Profile)
- Protocol: ASCII (human readable).
The program sends a '?' (0x3f) to make request for a 12Bit ADC value (0... 4095). Then the program expects 4 decimal digits to be returned (timeout 1s).