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Step 6Programming Header/External Connections.
The watch is 'programmable'. An ICSP header is brought out to the back so that new firmware can be installed. The header is a row of low-profile female pin sockets I found at my local electronics store. The same thing can be had by cutting a quality DIP socket in half the long way. I connect my ICSP plug with a pin-header "gender-changer" - insert a piece of pin-header into the socket, then connect the ICSP plug to the pin header. You will need an ICSP programmer to put new software in the watch. A simple JDM2 ICSP programmer is included with the Cadsoft Eagle files.
When not used for programming, the ICSP header can be used for data collection, event logging, etc. All of the ICSP pins are available for use, as noted in the table below. The voltage meter pin (pin 1/6)is pretty much dedicated for that use because of the voltage divider.
Multimeter - ADC, I/O, with resistor divider. (PIN2, PORTA0/AN0)
MCLR - input only pin. Schmitt trigger input for noisy signals.(PIN1, RE3)
Vcc - +3 volts
Vss - ground pin
Data - Input/Output with interrupt on change, optional weak pull-up (PIN27, RB6)
Clock - I/O with interrupt on change, option weak pull-up (PIN28, RB7)
When not used for programming, the ICSP header can be used for data collection, event logging, etc. All of the ICSP pins are available for use, as noted in the table below. The voltage meter pin (pin 1/6)is pretty much dedicated for that use because of the voltage divider.
Multimeter - ADC, I/O, with resistor divider. (PIN2, PORTA0/AN0)
MCLR - input only pin. Schmitt trigger input for noisy signals.(PIN1, RE3)
Vcc - +3 volts
Vss - ground pin
Data - Input/Output with interrupt on change, optional weak pull-up (PIN27, RB6)
Clock - I/O with interrupt on change, option weak pull-up (PIN28, RB7)
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