STM32: SPI: SPI3W / SPI_DIRECTION_1LINE management

In case MISO is not passed at SPI init, then we consider a 3 wires SPI
configuration is requested, which corresponds to SPI_DIRECTION_1LINE
configuration parameter in STM32 HAL layer.

We're then handling this specific case of SPI_DIRECTION_1LINE,
in spi_master_write or spi_master_block_write, we call to HAL API

Author: mapellil

targets/TARGET_STM/stm_spi_api.c

@@ -156,7 +156,13 @@ void spi_init(spi_t *obj, PinName mosi, PinName miso, PinName sclk, PinName ssel
     handle->Instance = SPI_INST(obj);
     handle->Init.Mode              = SPI_MODE_MASTER;
     handle->Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_256;
-    handle->Init.Direction         = SPI_DIRECTION_2LINES;
+
+    if (miso != NC) {
+        handle->Init.Direction     = SPI_DIRECTION_2LINES;
+    } else {
+       handle->Init.Direction      = SPI_DIRECTION_1LINE;
+    }
+
     handle->Init.CLKPhase          = SPI_PHASE_1EDGE;
     handle->Init.CLKPolarity       = SPI_POLARITY_LOW;
     handle->Init.CRCCalculation    = SPI_CRCCALCULATION_DISABLE;
@@ -353,6 +359,10 @@ int spi_master_write(spi_t *obj, int value)
     struct spi_s *spiobj = SPI_S(obj);
     SPI_HandleTypeDef *handle = &(spiobj->handle);
 
+    if (handle->Init.Direction == SPI_DIRECTION_1LINE) {
+        return HAL_SPI_Transmit(handle, (uint8_t*)&value, 1, 10);
+    }
+
 #if defined(LL_SPI_RX_FIFO_TH_HALF)
     /*  Configure the default data size */
     if (handle->Init.DataSize == SPI_DATASIZE_16BIT) {
@@ -390,13 +400,31 @@ int spi_master_write(spi_t *obj, int value)
 int spi_master_block_write(spi_t *obj, const char *tx_buffer, int tx_length,
                            char *rx_buffer, int rx_length, char write_fill)
 {
+    struct spi_s *spiobj = SPI_S(obj);
+    SPI_HandleTypeDef *handle = &(spiobj->handle);
     int total = (tx_length > rx_length) ? tx_length : rx_length;
-
-    for (int i = 0; i < total; i++) {
-        char out = (i < tx_length) ? tx_buffer[i] : write_fill;
-        char in = spi_master_write(obj, out);
-        if (i < rx_length) {
-            rx_buffer[i] = in;
+    int i = 0;
+    if (handle->Init.Direction == SPI_DIRECTION_2LINES) {
+        for (i = 0; i < total; i++) {
+            char out = (i < tx_length) ? tx_buffer[i] : write_fill;
+            char in = spi_master_write(obj, out);
+            if (i < rx_length) {
+                rx_buffer[i] = in;
+            }
+        }
+    } else {
+        /* In case of 1 WIRE only, first handle TX, then Rx */
+        if (tx_length != 0) {
+            if (HAL_OK != HAL_SPI_Transmit(handle, (uint8_t*)tx_buffer, tx_length, tx_length*10)) {
+                /*  report an error */
+                total = 0;
+            }
+        }
+        if (rx_length != 0) {
+            if (HAL_OK != HAL_SPI_Receive(handle, (uint8_t*)rx_buffer, rx_length, rx_length*10)) {
+                /*  report an error */
+                total = 0;
+            }
         }
     }