Fix: Possible crash when multiple tasks accessed the SPI bus

This could happen when  the main loop and the web server callback accessed the  SPI bus at the same time  (e.g. to show the isConnected status)

lib/CMT2300a/cmt_spi3.c

@@ -3,10 +3,16 @@
 #include <driver/spi_master.h>
 #include <esp_rom_gpio.h> // for esp_rom_gpio_connect_out_signal
 
+SemaphoreHandle_t paramLock=NULL;
+#define SPI_PARAM_LOCK()    do {} while (xSemaphoreTake(paramLock, portMAX_DELAY) != pdPASS)
+#define SPI_PARAM_UNLOCK()  xSemaphoreGive(paramLock)
+
 spi_device_handle_t spi_reg, spi_fifo;
 
 void cmt_spi3_init(int8_t pin_sdio, int8_t pin_clk, int8_t pin_cs, int8_t pin_fcs, uint32_t spi_speed)
 {
+    paramLock = xSemaphoreCreateMutex();
+
     spi_bus_config_t buscfg = {
         .mosi_io_num = pin_sdio,
         .miso_io_num = -1, // single wire MOSI/MISO
@@ -62,7 +68,9 @@ void cmt_spi3_write(uint8_t addr, uint8_t dat)
         .tx_buffer = &tx_data,
         .rx_buffer = NULL
     };
+    SPI_PARAM_LOCK();
     ESP_ERROR_CHECK(spi_device_polling_transmit(spi_reg, &t));
+    SPI_PARAM_UNLOCK();
     delayMicroseconds(100);
 }
 
@@ -76,7 +84,9 @@ uint8_t cmt_spi3_read(uint8_t addr)
         .tx_buffer = &tx_data,
         .rx_buffer = &rx_data
     };
+    SPI_PARAM_LOCK();
     ESP_ERROR_CHECK(spi_device_polling_transmit(spi_reg, &t));
+    SPI_PARAM_UNLOCK();
     delayMicroseconds(100);
     return rx_data;
 }
@@ -92,11 +102,13 @@ void cmt_spi3_write_fifo(const uint8_t* buf, uint16_t len)
         .rx_buffer = NULL
     };
 
+    SPI_PARAM_LOCK();
     for (uint8_t i = 0; i < len; i++) {
         tx_data = ~buf[i]; // negate buffer contents
         ESP_ERROR_CHECK(spi_device_polling_transmit(spi_fifo, &t));
         delayMicroseconds(4); // > 4 us
     }
+    SPI_PARAM_UNLOCK();
 }
 
 void cmt_spi3_read_fifo(uint8_t* buf, uint16_t len)
@@ -110,9 +122,11 @@ void cmt_spi3_read_fifo(uint8_t* buf, uint16_t len)
         .rx_buffer = &rx_data
     };
 
+    SPI_PARAM_LOCK();
     for (uint8_t i = 0; i < len; i++) {
         ESP_ERROR_CHECK(spi_device_polling_transmit(spi_fifo, &t));
         delayMicroseconds(4); // > 4 us
         buf[i] = rx_data;
     }
+    SPI_PARAM_UNLOCK();
 }