RS-485 working

Author: jscott3201

crates/bacnet-gateway/src/config.rs

@@ -138,6 +138,63 @@ pub struct MstpConfig {
     pub max_master: u8,
     /// Network number for this transport.
     pub network_number: u16,
+    /// RS-485 direction control configuration (optional).
+    /// If omitted, assumes the hardware handles direction automatically
+    /// (USB RS-485 adapters, auto-direction transceivers).
+    #[serde(default)]
+    pub rs485: Option<Rs485Config>,
+}
+
+/// RS-485 direction control configuration.
+#[derive(Debug, Clone, Deserialize)]
+#[serde(tag = "mode")]
+pub enum Rs485Config {
+    /// Kernel RS-485 mode via TIOCSRS485 ioctl (Linux only).
+    /// The kernel toggles the UART's RTS pin for direction control.
+    /// Use when DE/RE is wired to the UART's RTS pin.
+    #[serde(rename = "kernel-rts")]
+    KernelRts {
+        /// Invert RTS polarity (default: false).
+        #[serde(default)]
+        invert_rts: bool,
+        /// Delay before send in microseconds (default: 0).
+        #[serde(default)]
+        delay_before_send_us: u32,
+        /// Delay after send in microseconds (default: 0).
+        #[serde(default)]
+        delay_after_send_us: u32,
+    },
+    /// GPIO direction control via Linux GPIO character device.
+    /// Toggles a GPIO pin for DE/RE control around each transmission.
+    /// Use for RS-485 hats where DE/RE is wired to a GPIO pin.
+    #[serde(rename = "gpio")]
+    Gpio {
+        /// GPIO chip device path (default: "/dev/gpiochip0").
+        #[serde(default = "default_gpio_chip")]
+        gpio_chip: String,
+        /// GPIO line number for DE/RE control.
+        gpio_line: u32,
+        /// If true, GPIO HIGH enables transmitter (default: true).
+        /// Most RS-485 transceivers (MAX485) use active-high DE.
+        #[serde(default = "default_true")]
+        active_high: bool,
+        /// Post-TX delay in microseconds before switching to RX mode (default: 200).
+        /// Covers the time for the last byte to leave the UART shift register.
+        #[serde(default = "default_post_tx_delay")]
+        post_tx_delay_us: u64,
+    },
+}
+
+fn default_gpio_chip() -> String {
+    "/dev/gpiochip0".to_string()
+}
+
+fn default_true() -> bool {
+    true
+}
+
+fn default_post_tx_delay() -> u64 {
+    200
 }
 
 fn default_baud_rate() -> u32 {

crates/bacnet-transport/src/mstp_serial.rs

@@ -107,8 +107,7 @@ impl TokioSerialPort {
         buf[2] = delay_after_send_us;
 
         // TIOCSRS485 = 0x542F
-        let ret =
-            unsafe { libc::ioctl(stream.as_raw_fd(), 0x542F, buf.as_mut_ptr()) };
+        let ret = unsafe { libc::ioctl(stream.as_raw_fd(), 0x542F, buf.as_mut_ptr()) };
         if ret < 0 {
             return Err(Error::Encoding(format!(
                 "TIOCSRS485 ioctl failed: {}",
@@ -185,12 +184,7 @@ impl<S: SerialPort> GpioDirectionPort<S> {
     /// - `line`: GPIO line number for DE/RE control (e.g., 18).
     /// - `active_high`: If true, GPIO HIGH enables the transmitter (most
     ///   common — MAX485 DE pin is active-high). If false, GPIO LOW enables TX.
-    pub fn new(
-        inner: S,
-        gpio_chip: &str,
-        line: u32,
-        active_high: bool,
-    ) -> Result<Self, Error> {
+    pub fn new(inner: S, gpio_chip: &str, line: u32, active_high: bool) -> Result<Self, Error> {
         Self::with_post_tx_delay(inner, gpio_chip, line, active_high, 0)
     }
 

docs/gateway.md

@@ -148,6 +148,32 @@ The gateway is configured via a TOML file (default: `gateway.toml`). The top-lev
 | `station_address` | `u8` | *(required)* | Station address (0--254). |
 | `max_master` | `u8` | `127` | Max master station address. |
 | `network_number` | `u16` | *(required)* | Network number for this transport. Must be 1--65534, unique. |
+| `rs485` | `Rs485Config?` | `None` | RS-485 direction control (see below). If omitted, assumes hardware auto-direction. |
+
+### `[transports.mstp.rs485]` -- RS-485 Direction Control (optional)
+
+Most USB RS-485 adapters handle direction switching automatically and need no configuration. For RS-485 hats or transceivers with manual DE/RE control, configure one of these modes:
+
+**GPIO mode** -- for RS-485 hats with a GPIO direction pin (e.g., Seeed Studio RS-485 Shield):
+
+```toml
+[transports.mstp.rs485]
+mode = "gpio"
+gpio_chip = "/dev/gpiochip0"  # default
+gpio_line = 18                 # GPIO pin number for DE/RE
+active_high = true             # true = HIGH enables transmitter (default)
+post_tx_delay_us = 200         # microseconds after TX before switching to RX (default: 200)
+```
+
+**Kernel RTS mode** -- for setups where DE/RE is wired to the UART's RTS pin:
+
+```toml
+[transports.mstp.rs485]
+mode = "kernel-rts"
+invert_rts = false             # true if DE is active-low (default: false)
+delay_before_send_us = 0       # microseconds delay before TX (default: 0)
+delay_after_send_us = 0        # microseconds delay after TX (default: 0)
+```
 
 ### `[bbmd]` -- BBMD Configuration
 
@@ -1089,7 +1115,7 @@ bdt = [
 ]
 ```
 
-### MS/TP on Linux
+### MS/TP on Linux (USB RS-485 adapter)
 
 ```toml
 [device]
@@ -1102,6 +1128,31 @@ baud_rate = 76800
 station_address = 1
 max_master = 127
 network_number = 3
+# No rs485 section needed — USB adapters handle direction automatically
+
+[transports.bip]
+broadcast = "192.168.1.255"
+network_number = 1
+```
+
+### MS/TP on Raspberry Pi (RS-485 Hat with GPIO)
+
+```toml
+[device]
+instance = 70002
+name = "Pi MS/TP Gateway"
+
+[transports.mstp]
+serial_port = "/dev/ttyS0"
+baud_rate = 76800
+station_address = 1
+max_master = 127
+network_number = 3
+
+# Seeed Studio RS-485 Shield: DE/RE on GPIO18
+[transports.mstp.rs485]
+mode = "gpio"
+gpio_line = 18
 
 [transports.bip]
 broadcast = "192.168.1.255"