modbus: add control for DE/nRE RS-485 transceiver signals

Add support to control DE/nRE RS-485 transceiver signals
over GPIO pins. Useful if the UART controller does not
support RS-485 mode.

Signed-off-by: Johann Fischer <johann.fischer@nordicsemi.no>

dts/bindings/misc/zephyr,modbus-serial.yaml

@@ -6,3 +6,22 @@ description: Modbus over serial line device
 compatible: "zephyr,modbus-serial"
 
 include: uart-device.yaml
+
+properties:
+    de-gpios:
+      type: phandle-array
+      required: false
+      description: Driver enable pin.
+
+        Driver enable pin (DE) of the RS-485 transceiver.
+        If connected directly the MCU pin should be configured
+        as active high.
+
+    re-gpios:
+      type: phandle-array
+      required: false
+      description: Receiver enable pin.
+
+        Receiver enable pin (nRE) of the RS-485 transceiver.
+        If connected directly the MCU pin should be configured
+        as active low.

subsys/modbus/mb_rtu_core.c

@@ -29,12 +29,69 @@ LOG_MODULE_REGISTER(mb_rtu, CONFIG_MODBUS_RTU_LOG_LEVEL);
 
 #define DT_DRV_COMPAT zephyr_modbus_serial
 
-#define MODBUS_DT_GET_DEV(port) {.dev_name = DT_INST_BUS_LABEL(port),},
+#define MB_RTU_DEFINE_GPIO_CFG(n, d)				\
+	static struct mb_rtu_gpio_config d##_cfg_##n = {	\
+		.name = DT_INST_GPIO_LABEL(n, d),		\
+		.pin = DT_INST_GPIO_PIN(n, d),			\
+		.flags = DT_INST_GPIO_FLAGS(n,  d),		\
+	};
+
+#define MB_RTU_DEFINE_GPIO_CFGS(n)				\
+	COND_CODE_1(DT_INST_NODE_HAS_PROP(n, de_gpios),		\
+		    (MB_RTU_DEFINE_GPIO_CFG(n, de_gpios)), ())	\
+	COND_CODE_1(DT_INST_NODE_HAS_PROP(n, re_gpios),		\
+		    (MB_RTU_DEFINE_GPIO_CFG(n, re_gpios)), ())
+
+DT_INST_FOREACH_STATUS_OKAY(MB_RTU_DEFINE_GPIO_CFGS)
+
+#define MB_RTU_ASSIGN_GPIO_CFG(n, d)				\
+	COND_CODE_1(DT_INST_NODE_HAS_PROP(n, d),		\
+		    (&d##_cfg_##n), (NULL))
+
+#define MODBUS_DT_GET_DEV(n) {					\
+		.dev_name = DT_INST_BUS_LABEL(n),		\
+		.de = MB_RTU_ASSIGN_GPIO_CFG(n, de_gpios),	\
+		.re = MB_RTU_ASSIGN_GPIO_CFG(n, re_gpios),	\
+	},
 
 static struct mb_rtu_context mb_ctx_tbl[] = {
 	DT_INST_FOREACH_STATUS_OKAY(MODBUS_DT_GET_DEV)
 };
 
+static void mb_tx_enable(struct mb_rtu_context *ctx)
+{
+	if (ctx->de != NULL) {
+		gpio_pin_set(ctx->de->dev, ctx->de->pin, 1);
+	}
+
+	uart_irq_tx_enable(ctx->dev);
+}
+
+static void mb_tx_disable(struct mb_rtu_context *ctx)
+{
+	uart_irq_tx_disable(ctx->dev);
+	if (ctx->de != NULL) {
+		gpio_pin_set(ctx->de->dev, ctx->de->pin, 0);
+	}
+}
+
+static void mb_rx_enable(struct mb_rtu_context *ctx)
+{
+	if (ctx->re != NULL) {
+		gpio_pin_set(ctx->re->dev, ctx->re->pin, 1);
+	}
+
+	uart_irq_rx_enable(ctx->dev);
+}
+
+static void mb_rx_disable(struct mb_rtu_context *ctx)
+{
+	uart_irq_rx_disable(ctx->dev);
+	if (ctx->re != NULL) {
+		gpio_pin_set(ctx->re->dev, ctx->re->pin, 0);
+	}
+}
+
 #ifdef CONFIG_MODBUS_RTU_ASCII_MODE
 /* The function calculates an 8-bit Longitudinal Redundancy Check. */
 static uint8_t mb_ascii_get_lrc(uint8_t *src, size_t length)
@@ -192,8 +249,8 @@ static void mb_tx_ascii_frame(struct mb_rtu_context *ctx)
 	ctx->uart_buf_ptr = &ctx->uart_buf[0];
 
 	LOG_DBG("Start frame transmission");
-	uart_irq_rx_disable(ctx->dev);
+	mb_rx_disable(ctx);
-	uart_irq_tx_enable(ctx->dev);
+	mb_tx_enable(ctx);
 }
 #else
 static int mb_rx_ascii_frame(struct mb_rtu_context *ctx)
@@ -300,8 +357,8 @@ static void mb_tx_rtu_frame(struct mb_rtu_context *ctx)
 
 	LOG_HEXDUMP_DBG(ctx->uart_buf, ctx->uart_buf_ctr, "uart_buf");
 	LOG_DBG("Start frame transmission");
-	uart_irq_rx_disable(ctx->dev);
+	mb_rx_disable(ctx);
-	uart_irq_tx_enable(ctx->dev);
+	mb_tx_enable(ctx);
 }
 
 void mb_tx_frame(struct mb_rtu_context *ctx)
@@ -372,8 +429,8 @@ static void mb_cb_handler_tx(struct mb_rtu_context *ctx)
 	} else {
 		/* Disable transmission */
 		ctx->uart_buf_ptr = &ctx->uart_buf[0];
-		uart_irq_tx_disable(ctx->dev);
+		mb_tx_disable(ctx);
-		uart_irq_rx_enable(ctx->dev);
+		mb_rx_enable(ctx);
 	}
 }
 
@@ -408,7 +465,7 @@ static void mb_rx_handler(struct k_work *item)
 		return;
 	}
 
-	uart_irq_rx_disable(ctx->dev);
+	mb_rx_disable(ctx);
 
 	if (IS_ENABLED(CONFIG_MODBUS_RTU_ASCII_MODE) &&
 	    (ctx->ascii_mode == true)) {
@@ -422,7 +479,7 @@ static void mb_rx_handler(struct k_work *item)
 	} else if (IS_ENABLED(CONFIG_MODBUS_RTU_SERVER)) {
 		if (mbs_rx_handler(ctx) == false) {
 			/* Server does not send response, re-enable RX */
-			uart_irq_rx_enable(ctx->dev);
+			mb_rx_enable(ctx);
 		}
 	}
 }
@@ -487,7 +544,7 @@ static int mb_configure_uart(struct mb_rtu_context *ctx,
 	}
 
 	uart_irq_callback_user_data_set(ctx->dev, mb_uart_cb_handler, ctx);
-	uart_irq_rx_enable(ctx->dev);
+	mb_rx_enable(ctx);
 
 	if (baudrate <= 38400) {
 		ctx->rtu_timeout = (numof_bits * if_delay_max) / baudrate;
@@ -519,6 +576,36 @@ struct mb_rtu_context *mb_get_context(const uint8_t iface)
 	return ctx;
 }
 
+static int mb_configure_gpio(struct mb_rtu_context *ctx)
+{
+	if (ctx->de != NULL) {
+		ctx->de->dev = device_get_binding(ctx->de->name);
+		if (ctx->de->dev == NULL) {
+			return -ENODEV;
+		}
+
+		if (gpio_pin_configure(ctx->de->dev, ctx->de->pin,
+				       GPIO_OUTPUT_INACTIVE | ctx->de->flags)) {
+			return -EIO;
+		}
+	}
+
+
+	if (ctx->re != NULL) {
+		ctx->re->dev = device_get_binding(ctx->re->name);
+		if (ctx->re->dev == NULL) {
+			return -ENODEV;
+		}
+
+		if (gpio_pin_configure(ctx->re->dev, ctx->re->pin,
+				       GPIO_OUTPUT_INACTIVE | ctx->re->flags)) {
+			return -EIO;
+		}
+	}
+
+	return 0;
+}
+
 static struct mb_rtu_context *mb_cfg_iface(const uint8_t iface,
 					   const uint8_t node_addr,
 					   const uint32_t baud,
@@ -565,6 +652,10 @@ static struct mb_rtu_context *mb_cfg_iface(const uint8_t iface,
 		mbs_reset_statistics(ctx);
 	}
 
+	if (mb_configure_gpio(ctx) != 0) {
+		return NULL;
+	}
+
 	if (mb_configure_uart(ctx, baud, parity) != 0) {
 		LOG_ERR("Failed to configure UART");
 		return NULL;
@@ -638,8 +729,8 @@ int mb_rtu_disable_iface(const uint8_t iface)
 
 	ctx = &mb_ctx_tbl[iface];
 
-	uart_irq_tx_disable(ctx->dev);
+	mb_tx_disable(ctx);
-	uart_irq_rx_disable(ctx->dev);
+	mb_rx_disable(ctx);
 	k_timer_stop(&ctx->rtu_timer);
 
 	ctx->rxwait_to = 0;

subsys/modbus/mb_rtu_internal.h

@@ -23,6 +23,7 @@
 #define ZEPHYR_INCLUDE_MODBUS_RTU_INTERNAL_H_
 
 #include <zephyr.h>
+#include <drivers/gpio.h>
 #include <modbus/modbus_rtu.h>
 
 #ifdef CONFIG_MODBUS_RTU_FP_EXTENSIONS
@@ -78,6 +79,13 @@ struct mb_rtu_frame {
 	uint16_t crc;
 };
 
+struct mb_rtu_gpio_config {
+	const char *name;
+	const struct device *dev;
+	gpio_pin_t pin;
+	gpio_dt_flags_t flags;
+};
+
 #define MB_RTU_STATE_CONFIGURED		0
 
 struct mb_rtu_context {
@@ -99,6 +107,10 @@ struct mb_rtu_context {
 	atomic_t state;
 	/* Pointer to current position in buffer */
 	uint8_t *uart_buf_ptr;
+	/* Pointer to driver enable (DE) pin config */
+	struct mb_rtu_gpio_config *de;
+	/* Pointer to receiver enable (nRE) pin config */
+	struct mb_rtu_gpio_config *re;
 
 	/* Client's mutually exclusive access */
 	struct k_mutex iface_lock;