GPIO4 can't be used for UART when Ethernet is enabled
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- Posts: 4
- Joined: Tue Feb 27, 2024 12:15 pm
GPIO4 can't be used for UART when Ethernet is enabled
I'm using an ESP32-WROOM-U. When I try to use GPIO4 for UART when I have Ethernet enabled, it can't get an IP. Why is this? How can I fix this?
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- Posts: 9764
- Joined: Thu Nov 26, 2015 4:08 am
Re: GPIO4 can't be used for UART when Ethernet is enabled
You need to be a bit more specific: the ESP32-WROOM-U is a module that by itself does not have Ethernet capabilities, it needs an external PHY. What hardware are you using that has that module?
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- Posts: 4
- Joined: Tue Feb 27, 2024 12:15 pm
Re: GPIO4 can't be used for UART when Ethernet is enabled
I'm using an LAN8720 chip connected by a custom PCB, which works fine when I'm not using GPIO4 for UART.
TX EN: IO21
TX D0: IO19
TX D1: IO22
RX D0: IO25
RX D1: IO26
CRS DV: IO27
MDIO: IO18
MDC: IO23
REF CLK: IO0
RESET: IO17
LAN8720 ON: IO2
TX EN: IO21
TX D0: IO19
TX D1: IO22
RX D0: IO25
RX D1: IO26
CRS DV: IO27
MDIO: IO18
MDC: IO23
REF CLK: IO0
RESET: IO17
LAN8720 ON: IO2
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- Posts: 9764
- Joined: Thu Nov 26, 2015 4:08 am
Re: GPIO4 can't be used for UART when Ethernet is enabled
Can you share your code that initializes the Ethernet MAC and the GPIO?
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- Posts: 4
- Joined: Tue Feb 27, 2024 12:15 pm
Re: GPIO4 can't be used for UART when Ethernet is enabled
- #define ETH_PHY_ADDR 0
- #define ETH_PHY_RST_GPIO GPIO_NUM_17
- #define ETH_PHY_POWER_GPIO GPIO_NUM_2
- #define ETH_PHY_MDIO_GPIO GPIO_NUM_18
- #define ETH_PHY_MDC_GPIO GPIO_NUM_23
- esp_err_t Ethernet::init() {
- esp_err_t err;
- // Turn on LAN8720
- gpio_set_direction(ETH_PHY_POWER_GPIO, GPIO_MODE_OUTPUT);
- gpio_set_level(ETH_PHY_POWER_GPIO, 1);
- // Initialize the EMAC
- eth_esp32_emac_config_t config = ETH_ESP32_EMAC_DEFAULT_CONFIG();
- config.smi_mdc_gpio_num = ETH_PHY_MDC_GPIO;
- config.smi_mdio_gpio_num = ETH_PHY_MDIO_GPIO;
- config.clock_config = {
- .rmii = {.clock_mode = EMAC_CLK_EXT_IN, .clock_gpio = EMAC_CLK_IN_GPIO}};
- // Initialize the MAC and PHY
- eth_mac_config_t mac_config = ETH_MAC_DEFAULT_CONFIG();
- eth_phy_config_t phy_config = ETH_PHY_DEFAULT_CONFIG();
- phy_config.phy_addr = ETH_PHY_ADDR;
- phy_config.reset_gpio_num = ETH_PHY_RST_GPIO;
- mac = esp_eth_mac_new_esp32(&config, &mac_config);
- phy = esp_eth_phy_new_lan87xx(&phy_config);
- // Install the driver
- esp_eth_handle_t eth_handle = NULL;
- esp_eth_config_t eth_conf = ETH_DEFAULT_CONFIG(mac, phy);
- err = esp_eth_driver_install(ð_conf, ð_handle);
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "Ethernet driver installation failure: %s",
- esp_err_to_name(err));
- return err;
- }
- // Initialize TCP/IP network interface
- err = esp_netif_init();
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "Network Interface initialization failure: %s",
- esp_err_to_name(err));
- return err;
- }
- err = esp_event_loop_create_default();
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "Event loop creation failure: %s", esp_err_to_name(err));
- return err;
- }
- esp_netif_config_t netif_config = ESP_NETIF_DEFAULT_ETH();
- esp_netif_t* eth_netif = esp_netif_new(&netif_config);
- err = esp_netif_attach(eth_netif, esp_eth_new_netif_glue(eth_handle));
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "Network Interface attachment failure: %s",
- esp_err_to_name(err));
- return err;
- }
- // Register event handlers
- err = esp_event_handler_register(ETH_EVENT, ESP_EVENT_ANY_ID, &on_eth_event,
- NULL);
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "Ethernet event handler registration failure: %s",
- esp_err_to_name(err));
- return err;
- }
- err = esp_event_handler_register(IP_EVENT, IP_EVENT_ETH_GOT_IP, &on_got_ip,
- NULL);
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "IP event handler registration failure: %s",
- esp_err_to_name(err));
- return err;
- }
- // Start the Ethernet driver
- err = esp_eth_start(eth_handle);
- if (err != ESP_OK) {
- ESP_LOGE(TAG, "Ethernet start failure: %s", esp_err_to_name(err));
- return err;
- }
- return ESP_OK;
- }
Re: GPIO4 can't be used for UART when Ethernet is enabled
Not sure if relevant or helpful, but I previously found that JTAG was unusable when the EMAC is enabled, even though they don't share any pins. I never figured out why, but configured my project with macros to disable EMAC when I need to debug with JTAG.
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- Posts: 211
- Joined: Fri May 07, 2021 10:35 am
Re: GPIO4 can't be used for UART when Ethernet is enabled
That's strange... The only thing which crossed my mind is the GPIO4 can be IO MUXed to EMAC_TX_ER function (see section 4.10 IO_MUX Pad List in TRM). Therefore make sure the GPIO4 is properly configured.
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