I have updated the hardware slightly for the next batch of prototypes. The circuit board size and layout is almost exactly the same, and it is still in a TicTac box. The new v4 circuit diagram is below.
Essentially, I have just added a line from pin 17 of the PIC to pin 5 of the RN42. This allows me to hold the RN42 in reset. I updated the PIC code to do this if the battery voltage is too low on start (below 3.6V). This means it is impossible to connect via bluetooth if the battery is too dead. If you are connected, it will keep on discharging all the way past 3.6V. To provide some feedback to the user, on startup the green LED2 now flashes fast if the battery is full, if it is below 3.6V it flashes slow (1 second on/off).
There is also a test point (TP1) to access PIO4 on the RN42 if that is needed.
Essentially, I have just added a line from pin 17 of the PIC to pin 5 of the RN42. This allows me to hold the RN42 in reset. I updated the PIC code to do this if the battery voltage is too low on start (below 3.6V). This means it is impossible to connect via bluetooth if the battery is too dead. If you are connected, it will keep on discharging all the way past 3.6V. To provide some feedback to the user, on startup the green LED2 now flashes fast if the battery is full, if it is below 3.6V it flashes slow (1 second on/off).
There is also a test point (TP1) to access PIO4 on the RN42 if that is needed.
