ESP32 PPP over serial connection with a NULL modem example

[hussainhadi673]

Related area

Serial Interface

Hardware specification

ESP32S3

Is your feature request related to a problem?

I am trying to connect my linux laptop (configured as PPP server using PPPD) with esp32. I am unable to find any suitable example code on ESP32 to configure it as PPPos client to connect with a null modem. All the examples on the internet are for making ESP32 PPP connection with modems.

However I have found one example code in micro python that works perfectly and connect with the Linux machine:

`import machine
import time
uart = machine.UART(2, baudrate=9600, tx=13, rx=14)

import network
ppp = network.PPP(uart)
ppp.active(True)
ppp.connect()
ppp.ifconfig()
ppp.isconnected()`

I need the same code in C language.

Describe the solution you'd like

A code that connects my esp32 to a null modem

Describe alternatives you've considered

No response

Additional context

No response

I have checked existing list of Feature requests and the Contribution Guide

• I confirm I have checked existing list of Feature requests and Contribution Guide.

[me-no-dev]

We use the ESP-IDF PPP driver. Please ask there if they know what needs to be done and if it can even work. Once they give you an answer, we can try to make it work on our end.

[hussainhadi673]

Can you please mention their github, where I can approach them.

[hussainhadi673]

Or if anyone has already tailored their code to make it work with Null Modem can share please

[lbernstone]

https://github.com/espressif/esp-idf/issues

[hussainhadi673]

Thankyou

[hussainhadi673]

I have used the netif and ppp libraries to make PPP connection with a Null Modem. Now I can connect my linux and esp32 directly PPP over serial. here is the code.

#include "lwip/opt.h"
#include "lwip/sys.h"
#include "lwip/netif.h"
#include "netif/ppp/pppapi.h"
#include "netif/ppp/pppos.h"
#include "driver/uart.h"
#include "esp_netif.h"

// UART configuration
#define UART_PORT_NUM      UART_NUM_1
#define UART_BAUD_RATE     115200
#define UART_RX_PIN        10
#define UART_TX_PIN        11
#define UART_BUF_SIZE      1024

// PPP configuration
static ppp_pcb *ppp;
static struct netif ppp_netif;

// Function to handle PPP link status changes
static void ppp_link_status_cb(ppp_pcb *pcb, int err_code, void *ctx) {
    struct netif *pppif = (struct netif *)ctx;

    if (err_code == PPPERR_NONE) {
        printf("PPP connection established\n");
        printf("IP address: %s\n", ip4addr_ntoa(netif_ip4_addr(pppif)));
        printf("Gateway: %s\n", ip4addr_ntoa(netif_ip4_gw(pppif)));
        printf("Netmask: %s\n", ip4addr_ntoa(netif_ip4_netmask(pppif)));
        return;
    }

    printf("PPP connection lost: %s\n");
}

// Function to output PPP data over UART
static u32_t pppos_output_cb(ppp_pcb *pcb, u8_t *data, u32_t len, void *ctx) {
    uart_write_bytes(UART_PORT_NUM, (const char *)data, len);
    return len;
}

// Initialize UART
void uart_init() {
    uart_config_t uart_config = {
        .baud_rate = UART_BAUD_RATE,
        .data_bits = UART_DATA_8_BITS,
        .parity = UART_PARITY_DISABLE,
        .stop_bits = UART_STOP_BITS_1,
        .flow_ctrl = UART_HW_FLOWCTRL_DISABLE
    };
    uart_param_config(UART_PORT_NUM, &uart_config);
    uart_set_pin(UART_PORT_NUM, UART_TX_PIN, UART_RX_PIN, UART_PIN_NO_CHANGE, UART_PIN_NO_CHANGE);
    uart_driver_install(UART_PORT_NUM, UART_BUF_SIZE * 2, 0, 0, NULL, 0);
}

// Main application
void setup() {
    // Initialize TCP/IP stack
    esp_netif_init();

    // Initialize UART
    uart_init();

    // Create PPPoS interface
    ppp = pppapi_pppos_create(&ppp_netif, pppos_output_cb, ppp_link_status_cb, &ppp_netif);
    if (ppp == NULL) {
        printf("Failed to create PPPoS interface\n");
        return;
    }

    // Set PPP as the default interface
    pppapi_set_default(ppp);

    // Connect PPP
    pppapi_connect(ppp, 0);
}

void loop() {
    uint8_t data[UART_BUF_SIZE];
    int len = uart_read_bytes(UART_PORT_NUM, data, UART_BUF_SIZE, 20 / portTICK_PERIOD_MS);
    if (len > 0) {
        pppos_input(ppp, data, len);
    }
    vTaskDelay(10 / portTICK_PERIOD_MS);
}