# Deck API

The Deck API allows to easily communicates with decks installed on the Crazyflie.

If you want to get started you can follow the howto to get your code running.

## Deck drivers

Decks are enumerated automatically using a One Wire (OW) memory soldered on the deck PCB. The Deck driver API is using a declarative syntax to register deck drivers and initialize them when the proper deck is installed.

### Minimal driver

This is a minimal deck driver, myled.c:

#include "deck.h"

void myledInit(DeckInfo *info)
{
pinMode(DECK_GPIO_IO1, OUTPUT);     // Set my Led pin to output
digitalWrite(DECK_GPIO_IO1, HIGH);  // Light it up
}

bool myledTest()
{
return true;
}

const DeckDriver myled_driver = {
.vid = 0,
.pid = 0,
.name = "meMyled",

.usedGpio = DECK_USING_IO_1,

.init = myledInit,
.test = myledTest,
};

DECK_DRIVER(myled_driver);

• At startup the decks are enumerated and if a deck has the name "meMyled", it will be initialized.
• Init is called on all initialized driver and then test is called.
• The init and test functions are both optional (we have some board with only init and event some with only test). If absent just remove the .init or .test initialization.
• In this mode no task are created so to run some code at regular intervale the code needs to deal with freeRtos or with the other parts of the Crazyflie code.

To compile the driver, place it in deck/drivers/src/ and add it to the Kbuild file:

obj-y += myled.o


### Forcing initialization of a driver

The deck driver will be initialized only if a deck is connected with the right OW memory content. During development it is possible to force the initialization of a deck by setting the CONFIG_DECK_FORCE config option to "meMyled" in your .config either by hand or using make menuconfig.

### Driver declaration API

DECK_DRIVER(const struct DeckDriver)

To register a deck driver the DECK_DRIVER() macro should be called with a deck structure as argument.

#### DeckDriver structure

typedef struct deck_driver {
/* Identification of the deck (written in the board) */
uint8_t vid;
uint8_t pid;
char *name;

/*
* Peripheral and Gpio used _directly_ by the driver.
*
* Include the pin in usedGpio if it's used directly by the driver, do not
* add the pin to usedGpio if it used as part of a peripheral.
*
* For example: If a deck driver uses SPI we add DECK_USING_SPI to
* usedPeriph. If the deck uses the MOSI, MISO or SCK pins for other stuff
* than SPI it would have to specify DECK_USING_[PA7|PA6|PA5].
*
*/
uint32_t usedPeriph;
uint32_t usedGpio;

/* Required system properties */
StateEstimatorType requiredEstimator;