GPIO configuration parameters include setting the pin as input or output, output mode as push-pull or open-drain, and pull-up/pull-down settings. Push-pull mode uses two MOSFETs to actively push or pull the output high or low, while open-drain uses one MOSFET that can only pull low and requires an external pull-up resistor. Pull-up or pull-down resistors are used to prevent floating inputs by connecting pins high or low when not driven. GPIO speed controls the slew rate for rise and fall times.

1. GPIO and Clock
Configuration

2. GPIO Interface
GPIO Output:
LED
LCD
7 –segment
GPIO Input:
Key/switch
Keypad

3. What are the GPIO Configuration
parameters???

4. GPIO Configuration
GPIO_Input / GPIO_Output
GPIO_Output:
GPIO_Output level: Low/High
GPIO mode: Output push pull or open drain
GPIO pull-up/pull-down: pull-up / pull-down / no pull-up no pull-
down
Maximum Output Speed: Low / Medium / High

5. GPIO Configuration
What is Push-Pull &
What is Open Drain????

6. GPIO Configuration:
Push pull
• Two MOSFETs: one connected toVcc & other
connected to Ground
• Output goes Low, it is connected to ground
through n-channel MOSFET
• Output goes High, it is connected toVcc
through p-channel MOSFET
• Output  Low, actively ‘pulled’ to Ground
• Output  High, actively ‘pushed’ toVcc

7. GPIO Configuration:
Push pull

8. GPIO Configuration:
OPEN Drain
• Only one MOSFET; only n-channel MOSFET
• Drain of MOSFET taken out of IC
• Only active in one direction
• It can pull the towards Ground
• Cannot drive toVcc (High)
• Switch OFF  Output Floating
• Needs a Pull-up resistor

9. GPIO Configuration:
Pull-up / pull-down
• In Digital circuits, pin must be connected to
either HIGH or LOW
• Pin should not be left unconnected (floating)
• When floating, undetermined state (can be
HIGH or LOW or not both)
• To Correct, connect a resistor from signal line
toVcc or Ground
• Resistor will either pull-up signal pin toVcc
• Or pull-down to Ground
Pull-up
resistor
Pull-down
resistor
Output

10. GPIO Configuration:
GPIO Speed
• Controls the slew rate
• Rise time and fall time of output signal
• Good practice to keep slow slew rate
• Increase only when needed

11. GPIO Configuration:
GPIO Input
• Input with internal pull-up; input signal pulled-up toVcc
• Input with internal pull-down ; input signal pulled-down to
Ground
• Floating Input; Signal level follows the external signal
• No external signal; Schmitt trigger toggles between logical levels
induced by external noise on pin