Why cannot use IO5/IO10 for SPI-CS (ESP32)?

General
#1
  1. My goal is: [Use IO5 as gpio for spi-cs pin ]
  2. My actions are: [Enable SPI with spi.mosi_gpio=23, spi.sclk_gpio=18, spi.miso_gpio=spi.cs0_gpio=-1 to write data/command with ESP32’s VSPI module]
  3. The result I see is: [Tried using IO4 as gpio for spi-cs that is working. But not sure why the same code with IO5 as gpio for spi-cs does not work]
  4. My expectation & question is:

My config_schema as below:

  - ["spi.enable", true]
  - ["spi.mosi_gpio", 23]
  - ["spi.miso_gpio", -1]
  - ["spi.sclk_gpio", 18]
  - ["spi.cs0_gpio",  -1] #why IO5 not working???
  - ["myDev", "o", {title: "My Device"}]
  - ["myDev.cs_index", "i", 0, {title: "spi.cs*_gpio index, 0, 1 or 2"}]
  - ["myDev.spi_freq", "i", 80000000, {title: "SPI frequency"}]
  - ["myDev.cs_pin", "i", 4, {title: "CS pin gpio"}]

Code to test is :

static void myDev_spi_write(const uint8_t *data, uint32_t size){

    struct mgos_spi *spi = mgos_spi_get_global();

    if (!spi) {
    LOG(LL_ERROR, ("SPI is disabled, set spi.enable=true"));
    return;
  }
  
  struct mgos_spi_txn txn = {
      .cs = -1,
      .mode = SPI_MODE,
      .freq = mgos_sys_config_get_myDev_spi_freq(),
  };
  txn.hd.tx_data   = data;
  txn.hd.tx_len    = size;
  txn.hd.dummy_len = 0;
  txn.hd.rx_len    = 0;
  txn.hd.rx_data   = NULL;
  mgos_spi_run_txn(spi, false, &txn);
}

Code to write with CS pin toggle by GPIO:

uint8_t cmd=0xFE;
mgos_gpio_write(mgos_sys_config_get_myDev_cs_pin(), 0); //CS 0
myDev_spi_write(&cmd, 1);
mgos_gpio_write(mgos_sys_config_get_myDev_cs_pin(), 1); //CS 1

The question is :
ESP32’s SPI seems very picky. CS= IO4 works but CS=IO5 doesn’t work. Also tried CS=IO10 but it didn’t work either. Other pins like CS=IO25 also working.

Why?

#2

bump I’m super keen to know!