pi 4 rts control just werks

Makefile

@@ -5,7 +5,10 @@ MK_DIR=mkdir -p
 CPP_SRCS= \
 	src/main.cpp
 
-CC=g++
+#TOOLCHAIN=armv7a-unknown-linux-gnueabihf
+TOOLCHAIN=
+CC=$(TOOLCHAIN)-g++
+SIZE=$(TOOLCHAIN)-size
 CFLAGS=-Og -Wall -fdata-sections -ffunction-sections -g3 -DDEBUG
 
 INCLUDES=\

README.md

@@ -0,0 +1,7 @@
+# Raspberry Pi Serial Bus Manager
+
+Pinout - we're using uart2, aka ttyAMA1
+
+| TX | RX | CTS | RTS |
+| --- | --- | --- | --- |
+| GPIO0/PIN 27 | GPIO1/PIN 28 | GPIO2/PIN 3 | GPIO3/PIN 5 |

src/main.cpp

@@ -1,7 +1,63 @@
+#include <cstring>
+#include <errno.h>
+#include <fcntl.h>
 #include <iostream>
+#include <linux/serial.h>
+#include <stdio.h>
+#include <unistd.h>
 
-int main(int argc, char** argv)
+/* Include definition for RS485 ioctls: TIOCGRS485 and TIOCSRS485 */
+#include <sys/ioctl.h>
+
+int main()
 {
-	std::cout << "Hello" << std::endl;
+	uint8_t send_buffer[14] = {0x7E, 0x01, 0x02, 8,	   0x01, 0x02, 0x03,
-	std::cout << "Hello" << std::endl;
+							   0x7D, 0x5E, 0x05, 0x06, 0x07, 0x08, 0xFF};
+
+	/* Open your specific device (e.g., /dev/mydevice): */
+	int fd = open("/dev/ttyAMA1", O_RDWR);
+	if (fd < 0)
+	{
+		/* Error handling. See errno. */
+		fprintf(stderr, "Failed... error:%s", strerror(errno));
+	}
+
+	struct serial_rs485 rs485conf;
+
+	/* Enable RS485 mode: */
+	rs485conf.flags |= SER_RS485_ENABLED;
+
+	/* Set logical level for RTS pin equal to 1 when sending: */
+	rs485conf.flags |= SER_RS485_RTS_ON_SEND;
+	/* or, set logical level for RTS pin equal to 0 when sending: */
+	rs485conf.flags &= ~(SER_RS485_RTS_ON_SEND);
+
+	/* Set logical level for RTS pin equal to 1 after sending: */
+	rs485conf.flags |= SER_RS485_RTS_AFTER_SEND;
+	/* or, set logical level for RTS pin equal to 0 after sending: */
+	rs485conf.flags &= ~(SER_RS485_RTS_AFTER_SEND);
+
+	// /* Set rts delay before send, if needed: */
+	// rs485conf.delay_rts_before_send = ...;
+
+	// /* Set rts delay after send, if needed: */
+	// rs485conf.delay_rts_after_send = ...;
+
+	/* Set this flag if you want to receive data even while sending data */
+	// rs485conf.flags |= SER_RS485_RX_DURING_TX;
+
+	if (ioctl(fd, TIOCSRS485, &rs485conf) < 0)
+	{
+		/* Error handling. See errno. */
+	}
+
+	/* Use read() and write() syscalls here... */
+	ssize_t rc = 0;
+	write(fd, send_buffer, 14);
+
+	/* Close the device when finished: */
+	if (close(fd) < 0)
+	{
+		/* Error handling. See errno. */
+	}
 }