Ethernet functionality is broken if MCPWM is enabled

[rob-bits]

Board

Closed source product with ESP32-Wrover-IE.N16R8

Device Description

It is an unique designed acquisition device. The following ESP32 functionalities are used (so far):

• Ethernet / Webserver function, RTL8201 phy, 50MHz clock connected to GPIO0 and inverted signal connected to REF clock of the PHY
• SPI - connected to ADC 20MHz SCLK, MISO/MOSI lines used, 16bit data, CS streched x4 burst transfer, period of 20us
• x2 channel PWM with MCPWM

Hardware Configuration

<style> </style>

GPIO	Notes	Assigment
35	input only	MISO
32		MOSI
33		SCLK
25	EMAC_RXD0	MAC_RXD0(RMII)
26	EMAC_RXD1	MAC_RXD1(RMII)
27	EMAC_RX_DV	MAC_RX_CRS_DV
14	EMAC_TXD2	I2C_SDA
12	EMAC_TXD3	I2C_SCL
13	EMAC_RX_ER	CS
15	Strapping pin, EMAC_RXD3	PWM1
2	Strapping pin, bootloader low	PWM2
0	Strapping pin, bootloader low	MAC_CLK_IN
18	DIO(RMII)	DIO(RMII)
19	EMAC_TXD0	MAC_TXD0(RMII)
21	EMAC_TX_EN	MAC_TX_EN(RMII)
RXD0		SerialRXD
TXD0	EMAC_RXD2	SerialTXD
22	EMAC_TXD1	MAC_TXD1(RMII)
23		MDC(RMII)

Version

v2.0.6

IDE Name

PlatformIO

Operating System

Windows 10

Flash frequency

40

PSRAM enabled

yes

Upload speed

115200

Description

If the MCPWM is configured and started (pwm_init() called) the ethernet stops working. Events are not generated. If the MCPWM does not configured (pwm_init() does not called) the ethernet works properly. I have issues ethernet + SPI as well but I could not strip down the closed source firmware to share a test code.

Sketch

/*
    This sketch shows the Ethernet event usage
*/
#include <Arduino.h>
#include <ETH.h>

#include "esp_log.h"
#include "esp_check.h"

#include "soc/mcpwm_periph.h" //for mcpwm_periph_signals
#include "driver/mcpwm.h"
#include "soc/mcpwm_struct.h"
#include "esp_rom_gpio.h" //for esp_rom_gpio_connect_out_signal

static bool eth_connected = false;

const int PS_PHY_EN = 4; 
const int START_DELAY_MS = 5000; //miliseconds

void WiFiEvent(WiFiEvent_t event)
{
  switch (event) {
    case ARDUINO_EVENT_ETH_START:
      Serial.println("ETH Started");
      //set eth hostname here
      ETH.setHostname("esp32-ethernet");
      break;
    case ARDUINO_EVENT_ETH_CONNECTED:
      Serial.println("ETH Connected");
      break;
    case ARDUINO_EVENT_ETH_GOT_IP:
      Serial.print("ETH MAC: ");
      Serial.print(ETH.macAddress());
      Serial.print(", IPv4: ");
      Serial.print(ETH.localIP());
      if (ETH.fullDuplex()) {
        Serial.print(", FULL_DUPLEX");
      }
      Serial.print(", ");
      Serial.print(ETH.linkSpeed());
      Serial.println("Mbps");
      eth_connected = true;
      break;
    case ARDUINO_EVENT_ETH_DISCONNECTED:
      Serial.println("ETH Disconnected");
      eth_connected = false;
      break;
    case ARDUINO_EVENT_ETH_STOP:
      Serial.println("ETH Stopped");
      eth_connected = false;
      break;
    default:
      break;
  }
}

void testClient(const char * host, uint16_t port)
{
  Serial.print("\nconnecting to ");
  Serial.println(host);

  WiFiClient client;
  if (!client.connect(host, port)) {
    Serial.println("connection failed");
    return;
  }
  client.printf("GET / HTTP/1.1\r\nHost: %s\r\n\r\n", host);
  while (client.connected() && !client.available());
  while (client.available()) {
    Serial.write(client.read());
  }

  Serial.println("closing connection\n");
  client.stop();
}

void pwm_init()
{     
  mcpwm_config_t pwm_config;
  pwm_config.frequency = 12500; //20;    //frequency = 110Hz
  pwm_config.cmpr_a = 0;       //duty cycle of PWMxA = 60.0%
  pwm_config.cmpr_b = 0;       //duty cycle of PWMxA = 60.0%
  pwm_config.counter_mode = MCPWM_UP_COUNTER;
  pwm_config.duty_mode = MCPWM_DUTY_MODE_0;

  //REF1
  mcpwm_init(MCPWM_UNIT_0, MCPWM_TIMER_0, &pwm_config);   //Configure PWM0A & PWM0B with above settings

  mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_A,50);
  mcpwm_set_duty_type(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_A, MCPWM_DUTY_MODE_0);

  mcpwm_set_duty(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_B,50);
  mcpwm_set_duty_type(MCPWM_UNIT_0, MCPWM_TIMER_0, MCPWM_OPR_B, MCPWM_DUTY_MODE_0);
  
  //configure GPIO
  gpio_set_direction((gpio_num_t) 15, GPIO_MODE_INPUT_OUTPUT);
  gpio_set_direction((gpio_num_t) 2, GPIO_MODE_INPUT_OUTPUT);
  gpio_set_direction((gpio_num_t) 20, GPIO_MODE_INPUT_OUTPUT);

  esp_rom_gpio_connect_out_signal((gpio_num_t)15, mcpwm_periph_signals.groups[MCPWM_UNIT_0].operators[MCPWM0B / 2].generators[MCPWM0B % 2].pwm_sig, 0, 0);
  esp_rom_gpio_connect_out_signal((gpio_num_t)2, mcpwm_periph_signals.groups[MCPWM_UNIT_0].operators[MCPWM0B / 2].generators[MCPWM0A % 2].pwm_sig, 0, 0);
  esp_rom_gpio_connect_out_signal((gpio_num_t)20, mcpwm_periph_signals.groups[MCPWM_UNIT_0].operators[MCPWM0A / 2].generators[MCPWM0A % 2].pwm_sig, 0, 0);

  mcpwm_start(MCPWM_UNIT_0, MCPWM_TIMER_0);
}

void setup()
{
  Serial.begin(115200);

  log_e("Initialization is starting");
  delay(START_DELAY_MS);

  pinMode(PS_PHY_EN, OUTPUT);
  digitalWrite(PS_PHY_EN, LOW);
  delay(200);
  digitalWrite(PS_PHY_EN, HIGH);
  delay(200);

  pwm_init();
  
  WiFi.onEvent(WiFiEvent);
  ETH.begin(ETH_PHY_ADDR, PS_PHY_EN, ETH_PHY_MDC, ETH_PHY_MDIO, ETH_PHY_RTL8201, ETH_CLOCK_GPIO0_IN, false);
}


void loop()
{
  if (eth_connected) {
    testClient("google.com", 80);
  }
  delay(10000);
}

Debug Message

Log message from normal operation:
rst:0x1 (POWERON_RESET),boot:0x23 (DOWNLOAD_BOOT(UART0/UART1/SDIO_REI_REO_V2))
waiting for download
ets Jul 29 2019 12:21:46

rst:0x1 (POWERON_RESET),boot:0x33 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0030,len:1184
load:0x40078000,len:13104
load:0x40080400,len:3036
entry 0x400805e4
[     6][D][esp32-hal-cpu.c:244] setCpuFrequencyMhz(): PLL: 480 / 2 = 240 Mhz, APB: 80000000 Hz
[    29][E][main.cpp:76] setup(): Initialization is starting
[  8367][V][WiFiGeneric.cpp:437] _arduino_event_cb(): Ethernet Started
[  8367][D][WiFiGeneric.cpp:931] _eventCallback(): Arduino Event: 18 - ETH_START
ETH Started[  8370][V][WiFiGeneric.cpp:430] _arduino_event_cb(): Ethernet Link Up

[  8380][D][WiFiGeneric.cpp:931] _eventCallback(): Arduino Event: 20 - ETH_CONNECTED
ETH Connected
[ 10371][V][WiFiGeneric.cpp:434] _arduino_event_cb(): Ethernet Link Down
[ 10371][D][WiFiGeneric.cpp:931] _eventCallback(): Arduino Event: 21 - ETH_DISCONNECTED
ETH Disconnected
[ 14371][V][WiFiGeneric.cpp:430] _arduino_event_cb(): Ethernet Link Up
[ 14371][D][WiFiGeneric.cpp:931] _eventCallback(): Arduino Event: 20 - ETH_CONNECTED
ETH Connected[ 14381][V][WiFiGeneric.cpp:445] _arduino_event_cb(): Ethernet got newip:192.168.0.16

[ 14384][D][WiFiGeneric.cpp:931] _eventCallback(): Arduino Event: 22 - ETH_GOT_IP
[ 14389][D][WiFiGeneric.cpp:1032] _eventCallback(): ETH IP: 192.168.0.16, MASK: 255.255.255.0, GW: 192.168.0.1
ETH MAC: 90:38:0C:B0:7A:5F, IPv4: 192.168.0.16, FULL_DUPLEX, 100Mbps

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closing connection

Bad operation:

rst:0x1 (POWERON_RESET),boot:0x33 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:2
load:0x3fff0030,len:1184
load:0x40078000,len:13104
load:0x40080400,len:3036
entry 0x400805e4
[     6][D][esp32-hal-cpu.c:244] setCpuFrequencyMhz(): PLL: 480 / 2 = 240 Mhz, APB: 80000000 Hz
[    29][E][main.cpp:111] setup(): Initialization is starting
[  9468][V][WiFiGeneric.cpp:437] _arduino_event_cb(): Ethernet Started
[  9468][D][WiFiGeneric.cpp:931] _eventCallback(): Arduino Event: 18 - ETH_START
ETH Started

Other Steps to Reproduce

Platformio configuration:

[env:esp-wrover-kit]
platform = espressif32@^5.3.0
board = esp-wrover-kit
framework = arduino
monitor_speed = 115200
build_flags = -DCORE_DEBUG_LEVEL=5

I have checked existing issues, online documentation and the Troubleshooting Guide

• I confirm I have checked existing issues, online documentation and Troubleshooting guide.

[me-no-dev]

I see that you are trying to use GPIO20 for PWM and also that GPIO15 does have RMII functionality. What if you do not start MCPWM on those two pins? Does IO2 work?

[rob-bits]

I see that you are trying to use GPIO20 for PWM and also that GPIO15 does have RMII functionality. What if you do not start MCPWM on those two pins? Does IO2 work?

Good catch! I am checking.
The GPIO20 is used to monitor a delayed MCPWM signal state. I have to check the state of a delayed PWM signal at a specific time. And I do not have additional outputs so I am using an internal signal as @Esp_sprite suggested on esp32.com forum:
https://esp32.com/viewtopic.php?f=13&t=31171

[rob-bits]

gpio_set_direction((gpio_num_t) 20, GPIO_MODE_INPUT_OUTPUT);

...
esp_rom_gpio_connect_out_signal((gpio_num_t)20, mcpwm_periph_signals.groups[MCPWM_UNIT_0].operators[MCPWM0A / 2].generators[MCPWM0A % 2].pwm_sig, 0, 0);

Please double check usage of GPIO20. ESP32 does not have output at GPIO20, see TRM Section "4 IO_MUX and GPIO Matrix (GPIO, IO_MUX)". However, the strange thing is that gpio_set_direction allowed you to configure it. I'll try to get more information internally and let you know later.

See my comment before yours. The GPIO20 is an undocumented internal signal, it is used as a loopback signal. It would be nice if that would be listed on the documentation.

[kostaond]

I see, I didn't know about it. Regarding GPIO15, you don't have to worry about it. It is used for only when PHY is connected via MII.

[rob-bits]

Okay, so the thing is, if the esp_rom_gpio_connect_out_signal() is called for any of the three GPIO (2, 15, 20) the ethernet is broken. If the function is not called at all the ethernet works however I do not have PWM signals on the output.

So if I remove the function call from the pwm_init() function and still call the pwm_init() the ethernet works. PWM signals does not.

Edit:
Can I enable the PWM signal without calling esp_rom_gpio_connect_out_signal() ?

Can you share the code inside this function? I know it is in the ROM but it would be helpful to understand what is the issue.

[mrengineer7777]

esp_rom_gpio_connect_out_signal() appears to be a core function of ESP-IDF. I was not able to find the source code, but it is referenced in many functions for IO.

[rob-bits]

Yes, I noticed, other people also was wondering the function of this. However as the name of the function and the header suggests, this function relates to the configuration of the IO mux and the GPIO matrix. The Technical Reference Manual is describing these registers so I guess I can write my function to enable the proper function on the selected GPIO. If the error will still preswnt then it will be a chip bug probably.

[Jason2866]

Calling a bug when using a non documented function? Probably it works different as you assume.

[rob-bits]

Sure, if the source code of that function would be released, the situation would be much cleaner. And as I said I can implement my function to configure the IO Mux and GPIO Matrix so theoretically that function can be left out and I can verify the operation of MCPWM + Ethernet.

[rob-bits]

Calling a bug when using a non documented function? Probably it works different as you assume.

So I just did the testing. Configuring these registers (MCPWM0 OUTB signal -> GPIO2):

volatile gpio_dev_t* sgGPIO_LL = (((volatile gpio_dev_t*) DR_REG_GPIO_BASE ));
  sgGPIO_LL->func_out_sel_cfg[2].func_sel = 33; //pwm0_outb is routed to signal 33
  sgGPIO_LL->func_out_sel_cfg[2].oen_sel = 1; //If the signal should always be enabled as an output, set the GPIO_FUNCx_OEN_SEL bit 
  sgGPIO_LL->enable |= 0x04;

Breaks the ethernet. So this is not firmware or software stuff. I just configure the GPIO matrix registers. Configuring these bits the MCPWM signal appears at the output however the ethernet is broken (as it is in my example).

The values of these bits:

before ethernet initialization:
[ 5040][E][main.cpp:136] setup(): GPIO2 func sel:256, oen sel:0, enable:3968

before my configuration of these bits
[ 5442][E][main.cpp:109] pwm_init(): GPIO2 func sel:256, oen sel:0, enable:1085332

after my configuration of these bits
[ 5442][E][main.cpp:113] pwm_init(): GPIO2 func sel:33, oen sel:1, enable:1085332

Any idea what to check?

[rob-bits]

I did further testing and seems like GPIO2 causing the issue. If I assign the signal to 33, 14, 12, 13, 5,15, 20 GPIOs then the ethernet works fine. If I set for GPIO2 it got broken.

I repeated the testing with esp_rom_gpio_connect_out_signal() function and seems like the ethernet fails only with input parameter equals to 2. Seems like I messed something last time...

Anyway, any idea why cannot I use GPIO2 for MCPWM?

[kostaond]

Could you please try to call

gpio_hal_iomux_func_sel(YOUR_GPIO, PIN_FUNC_GPIO);

following
esp_rom_gpio_connect_out_signal call?

There not much special about GPIO2 as of I know. Only just it is used as bootstrap pin.

[rob-bits]

Could you please try to call

gpio_hal_iomux_func_sel(YOUR_GPIO, PIN_FUNC_GPIO);

following esp_rom_gpio_connect_out_signal call?

There not much special about GPIO2 as of I know. Only just it is used as bootstrap pin.

Hmm, I do not know what is happening. I have two project, one is configured with the example project that I shared here. It is using Arduino v2.0.6. And I have another project, the main fw for our device, where a plenty of other things are configured. That uses arduino and esp-idf framework (v4.4.3 with unique menuconfig configuration).

And after programming the main fw and reprogramming the example code now the MCPWM is working on GPIO2. Previously it was not working. I tried this with multiple programming tries before. And on Friday the ethernet did not work with any of the GPIO that I am using... So something odd is happening. Seems like something could be present in flash, after reprogramming when changing the esp-idf core, and that causes issues for me. I try to find out this now.

[rob-bits]

Ok I found out the issue is related to the hardware that we are using...

So I have this MCPWM signal (GPIO2) which goes over the lines of ethernet (EMAC_CLK_IN, EMAC_TXD0, MDIO, EMAC_TX_EN and MDC). And probably there is a crosstalk between the signals. It is a 4 layer board where one layer is dedicated for GND, and for 3.3V. However because of the component density there are small amount of some signals on the ground layers as well. Especially these ETH signals could not have a solid ground plane. See the image:

The MCPWM is connected to the pink colored trace.

Any idea which signal could be affected?