hdw-esp-now.h File Reference

Detailed Description

Date

Oct 29, 2018

Author

adam

Design Philosophy

ESP-NOW is a kind of connection-less Wi-Fi communication protocol that is defined by Espressif. This component manages ESP-NOW so that you don't have to. It provides a simple wrapper to broadcast a packet, espNowSend(), and passes all received packets through a callback given to initEspNow().

Swadges do not use any ESP-NOW security and do not pair with each other using ESP-NOW. All transmissions are broadcasts and all Swadges will receive all other transmissions. Two Swadges may 'pair' with each other by including the recipient's MAC address in a transmitted packet. This pairing can be done using p2pConnection.c.

This component can also facilitate communication between to Swadges using a Universal Asynchronous Receiver/Transmitter (UART) wired connection. The wired UART is significantly faster and significantly more reliable than the wireless one, but it does require a physical wire.

Swadges have USB-C ports and the wired connection reconfigures the D+ and D- pins within the USB cable to be serial RX and TX instead. This means that while the serial connection is active, USB is non-functional. It also means that one Swadge has to treat D+ as RX and D- as TX, while the other has to do the opposite and treat D+ as TX and D- as RX. If a Swadge mode uses wired connections, it's UI must have an options to assume either role (commonly Swadge A and Swadge B).

Usage

You don't need to call initEspNow(), checkEspNowRxQueue(), or deinitEspNow() . The system does at the appropriate time.

espNowUseWireless() and espNowUseSerial() may be used to switch between wireless connections and wired connections, respectively. espNowUseSerial() is also used to configure the RX and TX pins for UART communication.

To send a packet, call espNowSend(). When the packet transmission finishes, the hostEspNowSendCb_t callback passed to initEspNow() is called with a status of either ESP_NOW_SEND_SUCCESS or ESP_NOW_SEND_FAIL.

When a packet is received, the hostEspNowRecvCb_t callback passed to initEspNow() is called with the received packet.

Example

static void swadgeModeEspNowRecvCb(const uint8_t* mac_addr, const char* data, uint8_t len, int8_t rssi)
{
    printf("Received %d bytes\n", len);
}
 
static void swadgeModeEspNowSendCb(const uint8_t* mac_addr, esp_now_send_status_t status)
{
    printf("Sent packet: %d\n", status);
}
 
...
 
{
    initEspNow(&swadgeModeEspNowRecvCb, &swadgeModeEspNowSendCb,
        GPIO_NUM_19, GPIO_NUM_20, UART_NUM_1, ESP_NOW);
 
    while(1)
    {
        // Check for received packets
        checkEspNowRxQueue();
 
        // Send a test packet
        char testPacket[] = "TEST";
        espNowSend(testPacket, ARRAY_SIZE(testPacket));
    }
}

Go to the source code of this file.

Typedefs
typedef void(*	hostEspNowRecvCb_t) (const esp_now_recv_info_t *esp_now_info, const uint8_t *data, uint8_t len, int8_t rssi)
	A function typedef for a callback called when an ESP-NOW packet is received.
typedef void(*	hostEspNowSendCb_t) (const uint8_t *mac_addr, esp_now_send_status_t status)
	A function typedef for a callback called when an ESP-NOW packet transmission finishes.

Enumerations
enum	wifiMode_t { NO_WIFI , ESP_NOW , ESP_NOW_IMMEDIATE }
	The different WiFi modes. More...

Functions
esp_err_t	initEspNow (hostEspNowRecvCb_t recvCb, hostEspNowSendCb_t sendCb, gpio_num_t rx, gpio_num_t tx, uart_port_t uart, wifiMode_t wifiMode)
void	deinitEspNow (void)
esp_err_t	espNowUseWireless (void)
void	espNowUseSerial (bool crossoverPins)
void	espNowSend (const char *data, uint8_t len)
void	checkEspNowRxQueue (void)

Typedef Documentation

hostEspNowRecvCb_t

typedef void(* hostEspNowRecvCb_t) (const esp_now_recv_info_t *esp_now_info, const uint8_t *data, uint8_t len, int8_t rssi)

A function typedef for a callback called when an ESP-NOW packet is received.

Parameters

esp_now_info	Information about the transmission, including The MAC addresses
data	The received packet
len	The length of the received packet
rssi	The signal strength of the received packet

hostEspNowSendCb_t

typedef void(* hostEspNowSendCb_t) (const uint8_t *mac_addr, esp_now_send_status_t status)

A function typedef for a callback called when an ESP-NOW packet transmission finishes.

Parameters

mac_addr	The MAC address which was transmitted to
status	The transmission status, either ESP_NOW_SEND_SUCCESS or ESP_NOW_SEND_FAIL

Enumeration Type Documentation

wifiMode_t

enum wifiMode_t

The different WiFi modes.

Enumerator
NO_WIFI	WiFi is not used at all. This saves power.
ESP_NOW	ESP-NOW packets are delivered to Swadge modes from the main loop.
ESP_NOW_IMMEDIATE	ESP-NOW packets are delivered to Swadge modes from the interrupt.

Function Documentation

initEspNow()

esp_err_t initEspNow	(	hostEspNowRecvCb_t	recvCb,
		hostEspNowSendCb_t	sendCb,
		gpio_num_t	rx,
		gpio_num_t	tx,
		uart_port_t	uart,
		wifiMode_t	wifiMode )

Initialize ESP-NOW and attach callback functions. This uses wifi by default, but espNowUseSerial() may be called later to communicate over the given UART instead

Parameters

recvCb	A callback to call when data is sent
sendCb	A callback to call when data is received
rx	The receive pin when using serial communication instead of wifi. Use GPIO_NUM_NC for no GPIO
tx	The transmit pin when using serial communication instead of wifi. Use GPIO_NUM_NC for no GPIO
uart	The UART to use for serial communication. Use UART_NUM_MAX for no UART
wifiMode	The WiFi mode. If ESP_NOW_IMMEDIATE, then recvCb is called directly from the interrupt. If ESP_NOW, then recvCb is called from checkEspNowRxQueue()

Returns

The esp_err_t that occurred

deinitEspNow()

void deinitEspNow

(

void

)

This function is called to de-initialize ESP-NOW

espNowUseWireless()

esp_err_t espNowUseWireless

(

void

)

Start wifi and use it for communication

Returns

ESP_OK or an error that occurred

espNowUseSerial()

void espNowUseSerial

(

bool

crossoverPins

)

Start the UART and use it for communication

Parameters

crossoverPins

true to crossover the rx and tx pins, false to use them as normal.

espNowSend()

void espNowSend	(	const char *	data,
		uint8_t	len )

This is a wrapper for esp_now_send(). It also sets the wifi power with wifi_set_user_fixed_rate()

Parameters

data	The data to broadcast using ESP NOW
len	The length of the data to broadcast

checkEspNowRxQueue()

void checkEspNowRxQueue

(

void

)

Check the ESP NOW receive queue. If there are any received packets, send them to hostEspNowRecvCb()