Overview

Module grisp_gpio

• Description
• Data Types
• Function Index
• Function Details

Description

GRiSP General Purpose Input/Output (GPIO) API.

General Purpose Input / Output (GPIO) is used to control digital signals on a pin. The digital values 0 and 1 correspond to a low or high voltage respectively. On GRiSP the voltage for GPIO pins is 3.3V.

A pin can be controlled either as an output pin or an input pin. For an output pin, it is possible to set or get the current value. For an input pin, it is possible to get the current value.

Pin Mappings

For PMOD connectors, the number column (#) maps to the respective PMOD pin (see Figure 1).

PMOD Pin Numbers

• 4 × data, pins #1-4
• 1 × ground, pin #5
• 1 × 3.3V power, pin #6

• 8 × data, pins #1-4 and #7-10
• 1 × ground, pins #5 and #11
• 1 × 3.3V power, pins #6 and #12

Data Types

mode()

mode() = input | {output, value()}

opts()

opts() = #{mode => mode(), term() => term()}

pin()

pin() = atom()

ref()

abstract datatype: ref()

value()

value() = 0 | 1

Function Index

Function Details

get/1

Returns the current value of a pin.

Returns the actual value for input pins or the currently set value for output pins.

Examples

 1> LED1R = grisp_gpio:open(led1_r, #{mode => {output, 0}}).
 #Ref<0.2691682867.116916226.176944>
 2> grisp_gpio:get(LED1R).
 0
 3> grisp_gpio:set(LED1R, 1).
 ok
 2> grisp_gpio:get(LED1R).
 1

 1> Jumper1 = grisp_gpio:open(jumper_1, #{mode => input}).
 #Ref<0.2691682867.116916226.176944>
 2> grisp_gpio:get(Jumper1).
 0

 3> grisp_gpio:get(Jumper1).
 1

open/1

Equivalent to open(Pin, #{}).

open/2

Creates a reference to a GPIO pin. If no mode is given in the options, it defaults to {output, 0}.

Example

 1> grisp_gpio:open(led1_r, #{mode => {output, 0}}).
 #Ref<0.2691682867.116916226.176944>

 1> grisp_gpio:open(jumper_1, #{mode => input}).
 #Ref<0.2691682867.116916226.176944>

set/2

Sets the current value of an output pin.

Example

 1> LED1R = grisp_gpio:open(led1_r, #{mode => {output, 0}}).
 #Ref<0.2691682867.116916226.176944>
 2> grisp_gpio:set(LED1R, 0).
 ok

 3> grisp_gpio:set(LED1R, 1).
 ok

Overview

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