Add utilitary to disable JTAG access via USB in ftdi device.

scripts/log-serial/Makefile

@@ -0,0 +1,7 @@
+disable-jtag: disable-jtag.c
+	gcc -Wall -Wextra -O2 -o disable-jtag disable-jtag.c -lftdi
+
+clean:
+	rm -f disable-jtag
+
+.PHONY: all clean

scripts/log-serial/disable-jtag.c

@@ -0,0 +1,49 @@
+#include <ftdi.h>
+#include <stdio.h>
+
+int main() {
+  struct ftdi_context *ftdi;
+  int ret;
+
+  ftdi = ftdi_new();
+  if ((ret = ftdi_init(ftdi)) < 0) {
+    fprintf(stderr, "Failed to initialize FTDI context: %s\n",
+            ftdi_get_error_string(ftdi));
+    ftdi_free(ftdi);
+    return 1;
+  }
+
+  /* FT4232H
+   * Vendor ID: 0403h
+   * Device ID: 6011h
+   */
+  if ((ret = ftdi_usb_open_desc(ftdi, 0x0403, 0x6011, NULL, NULL)) < 0) {
+    fprintf(stderr, "Failed to open device: %s\n", ftdi_get_error_string(ftdi));
+    return 1;
+  }
+
+  // Device connected on Interface A
+  if ((ret = ftdi_set_interface(ftdi, INTERFACE_A)) < 0) {
+    fprintf(stderr, "Failed to select channel: %s\n",
+            ftdi_get_error_string(ftdi));
+    return 1;
+  }
+
+  // ADBUS7 disables AMC access. Enable bitbang mode for it.
+  if ((ret = ftdi_set_bitmode(ftdi, 0b10000000, BITMODE_BITBANG)) < 0) {
+    fprintf(stderr, "Failed to enable bit-bang mode: %s\n",
+            ftdi_get_error_string(ftdi));
+    return 1;
+  }
+
+  uint8_t value = 0b10000000;
+  if ((ret = ftdi_write_data(ftdi, &value, 1)) < 0) {
+    fprintf(stderr, "Failed to write data: %s\n", ftdi_get_error_string(ftdi));
+    return 1;
+  }
+
+  ftdi_usb_close(ftdi);
+  ftdi_deinit(ftdi);
+
+  return 0;
+}