diff --git a/inc/decls.h b/inc/decls.h
index 3303d052..ca8e87a7 100644
--- a/inc/decls.h
+++ b/inc/decls.h
@@ -10,6 +10,8 @@
  * See the file COPYING for more details, or visit <http://unlicense.org>.
  */
 
+#define CONFIG_SWD 1
+
 #include <stdint.h>
 #include <stdarg.h>
 #include <stddef.h>
diff --git a/inc/mcu/stm32f105_regs.h b/inc/mcu/stm32f105_regs.h
index d929c20d..3291c7eb 100644
--- a/inc/mcu/stm32f105_regs.h
+++ b/inc/mcu/stm32f105_regs.h
@@ -191,6 +191,7 @@ struct afio {
     uint32_t mapr2;      /* 1C: AF remap and debug I/O configuration #2 */
 };
 
+#define AFIO_MAPR_SWJ_CFG_ENABLED      (2u<<24)
 #define AFIO_MAPR_SWJ_CFG_DISABLED     (4u<<24)
 #define AFIO_MAPR_TIM4_REMAP_FULL      (1u<<12)
 #define AFIO_MAPR_TIM3_REMAP_FULL      (3u<<10)
diff --git a/src/gotek/board.c b/src/gotek/board.c
index af679ea1..1ef801c1 100644
--- a/src/gotek/board.c
+++ b/src/gotek/board.c
@@ -97,10 +97,12 @@ unsigned int board_get_buttons(void)
 unsigned int board_get_rotary(void)
 {
     unsigned int x = 3;
+#if !defined(CONFIG_SWD)
     if ((mcu_package != MCU_QFN32) && (ff_cfg.chgrst != CHGRST_pa14)) {
         /* Alternative location at PA13, PA14. */
         x &= gpioa->idr >> 13;
     }
+#endif
     if (mcu_package == MCU_LQFP64) {
         /* Original rotary header at PC10, PC11. */
         x &= gpioc->idr >> 10;
@@ -118,12 +120,14 @@ uint32_t board_rotary_exti_mask;
 void board_setup_rotary_exti(void)
 {
     uint32_t m = 0;
+#if !defined(CONFIG_SWD)
     if ((mcu_package != MCU_QFN32) && (ff_cfg.chgrst != CHGRST_pa14)) {
         /* Alternative location at PA13, PA14. */
         exti_route_pa(13);
         exti_route_pa(14);
         m |= m(13) | m(14);
     }
+#endif
     if (mcu_package == MCU_LQFP64) {
         /* Original rotary header at PC10, PC11. */
         exti_route_pc(10);
@@ -181,6 +185,11 @@ void board_init(void)
     pa_skip |= 0x0600;
 #endif
 
+#if defined(CONFIG_SWD)
+    /* PA13-14 (SWD) */
+    pa_skip |= 0x6000;
+#endif
+
     /* PB0,4,9 (floppy inputs). */
     pb_skip = 0x0211;
 
diff --git a/src/mcu_stm32f105.c b/src/mcu_stm32f105.c
index 38359dbc..1098750f 100644
--- a/src/mcu_stm32f105.c
+++ b/src/mcu_stm32f105.c
@@ -109,11 +109,23 @@ static void peripheral_init(void)
                     RCC_APB2ENR_TIM1EN);
     rcc->ahbenr = RCC_AHBENR_DMA1EN;
 
+#if defined(CONFIG_SWD)
+
+    /* Preserve PA13, PA14 as SWD. */
+    afio->mapr = AFIO_MAPR_SWJ_CFG_ENABLED;
+    gpioa->crl = 0x44444444u;
+    gpioa->crh = (gpioa->crh & 0x0ff00000u) | 0x40044444u;
+
+#else
+
     /* Turn off serial-wire JTAG and reclaim the GPIOs. */
     afio->mapr = AFIO_MAPR_SWJ_CFG_DISABLED;
 
     /* All pins in a stable state. */
     gpio_init(gpioa);
+
+#endif
+
     gpio_init(gpiob);
     gpio_init(gpioc);
 }