CORTEX Microcontroller and Joystick Quick Start Guide
Page 8 of 9
5. Analog Information: Analog lines are input only and read about 62 (0.2 volts) when open. When connected to a 0 to 5v
source, such as the VEX Potentiometer, you will read from near 0 (0 volts) to near 1023 (5 volts).
a. Circuit details:
i. Analog input range is 0 to +5 volts.
ii. Analog circuit has a 470k pull-up to +5 volts, a series 10k resistor and a 20k resistor to ground.
iii. Analog inputs also have a 1000 pF capacitor to ground on the processor side of the 10k resistor.
iv. 3 dB bandwidth: 16 kHz.
v. Circuit connections as shown.
6. Digital Information: When congured as an input, digital lines have a weak pull-up. When congured as an output,
digital lines drive 0 volts for a low and 3.3 volts for a high.
a. Circuit details, Digital Ports 1 through 12:
i. Digital input range is 0 to +5 volts.
ii. 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.
iii. Digital inputs also have a 1000 pF capacitor to ground on the processor side of the 1k resistor.
iv. 3 dB input bandwidth: 16 kHz.
v. Circuit connections as shown.
Analog Input
(Typical)
Weak Pull-up
In Processor
Digital Input Output
To Processor
20K
1000 PF
1000 PF
470 K
10 K
+5 V
3.3 V
1 K
Analog Port
Digital Port
b. Circuit details, SP Digital Port
i. Circuit SP is connected to the Digital-to-Analog-Converter (DAC) output of the User Processor.
ii. Factory default Hex le does not support the DAC output. Check your compiler for availability and use.
iii. SP is an Analog Output when congured 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.
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