Cortex Microcontroller and VEXnet Joystick User Guide
Page 13 of 14
10. Analog Information: Analog lines are input only and read about 0.2 volts when open.
Circuit details are as
follows:
a. Analog input range is 0 to +5 volts.
b. Analog to digital resolution is 12-bit, compiler resolution may vary.
c. Analog circuit has a 470k pull-up to +5 volts, a series 10k resistor and a 20k resistor to ground.
d. Analog inputs also have a 1000 pF capacitor to ground on the processor side of the 10k resistor.
e. 3 dB bandwidth: 16 kHz.
f. Circuit connections as shown.
Weak Pull-up
In Processor
Digital Input Output
1000 PF
3.3 V
1 K
Digital Port
Analog Input
(Typical)
To Processor
20K
1000 PF
470 K
10 K
+5 V
Analog Port
11. Digital Information: When configured as an input, digital lines have a weak pull-up.
When configured as an output,
digital lines drive 0 volts for a low and 3.3 volts for a high. Circuit details are as follows:
a. Digital input range is 0 to +5 volts.
b. Digital drive is primarily limited by the 1k series resistor, so it can output a 2v high into 2k-ohms to ground or a 0.8v
low into 7k-ohms to 3.3v.
c. Digital inputs also have a 1000 pF capacitor to ground on the processor side of the 1k resistor.
d. 3 dB input bandwidth: 150 kHz.
e. Circuit connections as shown.
12. Circuit details of the Digital-to-Analog Port, SP:
a. Circuit SP is connected to the Digital-to-Analog-Converter (DAC) output of the User Processor.
b. Factory default Hex file does not support the DAC output. Check your compiler for availability and use.
c. SP is an Analog Output when configured by compiler. Drive is primarily limited by a 5 kilo-ohm internal processor
resistance and by the 100 ohm series resistor. Output swing of the processor into an open load is 0.2v to 3.1v, typical.
