diff --git a/controller/.gitignore b/controller/.gitignore
new file mode 100644
index 0000000..97f90d8
--- /dev/null
+++ b/controller/.gitignore
@@ -0,0 +1 @@
+controller
diff --git a/controller/README.md b/controller/README.md
index e776b27..2ce00a6 100644
--- a/controller/README.md
+++ b/controller/README.md
@@ -1,12 +1,22 @@
 # Controller
 ## links
 * https://www.kernel.org/doc/Documentation/i2c/dev-interface
+* https://forum.arduino.cc/t/solved-cannot-get-correct-i2c-data-from-atmega8-into-raspberry-pi/1368337
 
 ## PINs
 * interal = physical = usage
 * 5 = 29 = reset peripheral devices
-* 0 = 27 = I2C SDA
-* 1 = 28 = I2C SCL
+* 0 = 10 = I2C SDA
+* 1 = 9 = I2C SCL
+
+## I2C
+* somehow the buildin I2C does not work anymore (maybe already damaged?)
+* add additional bus by using GPIOs:
+```
+$ fgrep i2c /boot/firmware/config.txt 
+dtparam=i2c_arm=on
+dtoverlay=i2c-gpio,bus=7,i2c_gpio_sda=10,i2c_gpio_scl=9
+```
 
 ## commands
 * reset peripheral devices: `gpioset gpiochip0 5=0`
diff --git a/controller/build.sh b/controller/build.sh
new file mode 100755
index 0000000..bf7b87f
--- /dev/null
+++ b/controller/build.sh
@@ -0,0 +1 @@
+gcc -o controller controller.c -li2c
diff --git a/controller/controller.c b/controller/controller.c
new file mode 100644
index 0000000..8310250
--- /dev/null
+++ b/controller/controller.c
@@ -0,0 +1,149 @@
+#include <linux/i2c-dev.h>
+#include <i2c/smbus.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdarg.h>
+
+#include "global.h"
+
+#define I2C_DEVICE "/dev/i2c-7"
+
+#define HEADING_SIM_UP "sim/autopilot/heading_up"
+#define HEADING_SIM_DOWN "sim/autopilot/heading_down"
+#define ALTITUDE_SIM_UP "sim/autopilot/altitude_up"
+#define ALTITUDE_SIM_DOWN "sim/autopilot/altitude_down"
+#define AIRSPEED_SIM_UP "sim/autopilot/airspeed_up"
+#define AIRSPEED_SIM_DOWN "sim/autopilot/airspeed_down"
+
+int i2c;
+
+struct device {
+  uint8_t address;       // I2C address of device
+  char *name;         // name of this device
+  char name1[3];      // first name to send on init of device
+  char *highCommand1; // command to use if TRIGGER_BIT_1 is set and HIGH_BIT_1 is set
+  char *lowCommand1;  // command to use if TRIGGER_BIT_1 is set and HIGH_BIT_1 is not set
+  int rrefRefresh1;   // refresh rate of subscribing rref
+  char *rref1;        // rref to subscribe to
+  char name2[3];      // second name to send on init of device
+  char *highCommand2; // command to use if TRIGGER_BIT_2 is set and HIGH_BIT_2 is set
+  char *lowCommand2;  // command to use if TRIGGER_BIT_2 is set and HIGH_BIT_2 is not set
+  int rrefRefresh2;   // refresh rate of subscribing rref
+  char *rref2;        // rref to subscribe to
+};
+
+struct rrefSubscription {
+  uint8_t address;
+  uint8_t triggerBit;
+};
+
+const struct device devices[] = {
+  {
+    0x08,
+    "Heading Speed",
+    {'H', 'D', 'G'},
+    HEADING_SIM_UP,
+    HEADING_SIM_DOWN,
+    200,
+    "sim/cockpit/autopilot/heading_mag",
+    {'S', 'P', 'D'},
+    AIRSPEED_SIM_UP,
+    AIRSPEED_SIM_DOWN,
+    200,
+    "sim/cockpit/autopilot/airspeed"
+  }
+};
+
+struct rrefSubscription rrefSubscriptions[2];
+
+void _log(char *format, ...) {
+  va_list args;
+  va_start(args, format);
+  vprintf(format, args);
+  va_end(args);
+}
+
+int setI2CAddress(uint8_t address) {
+  if (ioctl(i2c, I2C_SLAVE, address) < 0) {
+    _log("setting periphal address 0x%02X failed\n", address);
+    return 0;
+  } else {
+    return 1;
+  }
+}
+
+void sendI2CInit(struct device d) {
+  _log("Sending init to %s\n", d.name);
+  
+  int bufLen = 1 + 1 + sizeof(d.name1) + 1 + sizeof(d.name2);
+  char buf[bufLen];
+  int i = 0;
+  buf[i++] = DATA_RESET_BYTE;
+  buf[i++] = DATA_INIT_BYTE_1;
+  buf[i++] = d.name1[0];
+  buf[i++] = d.name1[1];
+  buf[i++] = d.name1[2];
+  buf[i++] = DATA_INIT_BYTE_2;
+  buf[i++] = d.name2[0];
+  buf[i++] = d.name2[1];
+  buf[i++] = d.name2[2];
+
+  setI2CAddress(d.address);
+  i2c_smbus_write_block_data(i2c, 0, bufLen, buf);
+}
+
+void sendI2CData(struct device d, uint8_t triggerBit, char *data, uint8_t dataLen) {
+  int bufLen = 1 + 1 + 1 + dataLen;
+  char buf[bufLen];
+  int i = 0;
+  buf[i++] = DATA_BYTE;
+  buf[i++] = triggerBit;
+  buf[i++] = dataLen;
+  for (int j = 0; j < dataLen; j++) {
+    buf[i++] = data[j];
+  }
+
+  setI2CAddress(d.address);
+  i2c_smbus_write_block_data(i2c, 0, bufLen, buf);
+}
+
+int main() {
+  __s32 i2cResponse;
+
+  i2c = open(I2C_DEVICE, O_RDWR);
+  if (i2c < 0) {
+    _log("Unable to open I2C device %s\n", I2C_DEVICE);
+    return 1;
+  }
+
+  while (1) {
+    int numDevices = sizeof(devices) / sizeof(struct device);
+    for (int i = 0; i < numDevices; i++) {
+      setI2CAddress(devices[i].address);
+      i2cResponse = i2c_smbus_read_byte_data(i2c, 0);
+      if (i2cResponse < 0) {
+        _log("I2C read failed: %s (%d)\n", strerror(errno), errno);
+      }
+
+      if (i2cResponse == DATA_RESET_BYTE) {
+        sendI2CInit(devices[i]);
+        sendI2CData(devices[i], TRIGGER_BIT_1, "xxx", 3);
+        sendI2CData(devices[i], TRIGGER_BIT_2, "xxx", 3);
+      } else if (i2cResponse == DATA_STOP_BYTE) {
+        // expect no forther data from device
+        continue;
+      } else {
+        // real data
+        _log("data: 0x%02x\n", i2cResponse);
+      }
+    }
+    usleep(10 * 1000);
+  }
+
+  close(i2c);
+}
diff --git a/controller/global.h b/controller/global.h
new file mode 120000
index 0000000..4adadf7
--- /dev/null
+++ b/controller/global.h
@@ -0,0 +1 @@
+../master/global.h
\ No newline at end of file