[TW#26803] spicommon_bus_initialize_io() does not accept SCLK on input pins when slave

[bu5hm4nn]

Environment

• Development Kit: [WiPy 3.0]
• Core: [ESP32D0WDQ6 revision 1]
• IDF version [Don't know how to get from platformio]
• Development Env: [PlatformIO]
• Operating System: [Any]
• Power Supply: [USB]

Problem Description

When using SPI as slave, the function spicommon_bus_initialize_io does not allow
SCLK to be on an input-only pin.

Expected Behavior

When the devices is configured as SPI Slave, then SCLK is an input-only signal and should be allowed on input-only pins.

Actual Behavior

Assert is thrown:

E (1554) spi: spicommon_bus_initialize_io(136): sclk not valid

Steps to repropduce

Try to initialize the SPI as slave with SCK on an input-only pin with the code. No wiring needed.

Code to reproduce this issue

// Configuration for the SPI bus
spi_bus_config_t buscfg =
{
    .mosi_io_num = GPIO_NUM_36,
    .miso_io_num = GPIO_NUM_22,
    .sclk_io_num = GPIO_NUM_37,
    .quadwp_io_num = -1,
    .quadhd_io_num = -1,
    .max_transfer_sz = SPI_SLAVE_BUFFER_SIZE,
    .flags = 0
};

// Configuration for the SPI slave interface
spi_slave_interface_config_t slvcfg = 
{
    .spics_io_num =     GPIO_NUM_38,
    .flags =            0,
    .queue_size =       1,
    .mode =             0,
    .post_setup_cb =    post_setup_callback,
    .post_trans_cb =    post_transport_callback
};

// Initialize SPI slave interface
assert( spi_slave_initialize( VSPI_HOST, &buscfg, &slvcfg, 1 ) == ESP_OK);

Debug Logs

E (1554) spi: spicommon_bus_initialize_io(136): sclk not valid

Proposed solution:

Check the SCLK pin in the same way as the MOSI pin:

//the SCLK should be output capble in master mode, or in DIO/QIO mode.
bool sclk_output = (flags&SPICOMMON_BUSFLAG_MASTER)!=0 || flags&SPICOMMON_BUSFLAG_DUAL;

and further down replace with this:

if (bus_config->sclk_io_num>=0) {
    temp_flag |= SPICOMMON_BUSFLAG_SCLK;
    if( sclk_output ) {
        SPI_CHECK(GPIO_IS_VALID_OUTPUT_GPIO(bus_config->sclk_io_num), "sclk not valid", ESP_ERR_INVALID_ARG);
    } else {
        SPI_CHECK(GPIO_IS_VALID_GPIO(bus_config->sclk_io_num), "sclk not valid", ESP_ERR_INVALID_ARG);
    }
    if (bus_config->sclk_io_num != spi_periph_signal[host].spiclk_iomux_pin) use_iomux = false;
} else {
    SPI_CHECK((flags&SPICOMMON_BUSFLAG_SCLK)==0, "sclk pin required.", ESP_ERR_INVALID_ARG);
}

[bu5hm4nn]

The fix is to do the same for SCLK as was done for MISO in this issue: #1736

[ginkgm]

@bu5hm4nn thanks, we will fix this

[trancefreak77]

When will this issue be fixed? I'm currently working on a schematic design where I have to know if CLK in slave mode can be assigned to an input only pin.

[ginkgm]

Hi @trancefreak77 .

It is now under internal review. And may appear on master soon.

[trancefreak77]

Thanks for the update.