diff --git a/include/libopencm3/stm32/l1/memorymap.h b/include/libopencm3/stm32/l1/memorymap.h
index 1b9cd10e..88974e2b 100644
--- a/include/libopencm3/stm32/l1/memorymap.h
+++ b/include/libopencm3/stm32/l1/memorymap.h
@@ -107,11 +107,10 @@
 #define AES_BASE			(PERIPH_BASE +  0x10000000)
 
 /* Device Electronic Signature */
-#define DESIG_FLASH_SIZE_BASE		(INFO_BASE + 0x8004C)
-#define DESIG_UNIQUE_ID_BASE		(INFO_BASE + 0x80050)
-#define DESIG_UNIQUE_ID0		MMIO32(DESIG_UNIQUE_ID_BASE)
-#define DESIG_UNIQUE_ID1		MMIO32(DESIG_UNIQUE_ID_BASE + 4)
-#define DESIG_UNIQUE_ID2		MMIO32(DESIG_UNIQUE_ID_BASE + 0x14)
+#define DESIG_FLASH_SIZE_BASE_CAT12		(INFO_BASE + 0x8004C)
+#define DESIG_FLASH_SIZE_BASE_CAT3456		(INFO_BASE + 0x800CC)
+#define DESIG_UNIQUE_ID_BASE_CAT12		(INFO_BASE + 0x80050)
+#define DESIG_UNIQUE_ID_BASE_CAT3456		(INFO_BASE + 0x800D0)
 
 /* ST provided factory calibration values @ 3.0V */
 #define ST_VREFINT_CAL			MMIO16(0x1FF80078)
diff --git a/lib/stm32/l1/Makefile b/lib/stm32/l1/Makefile
index 00d76fd2..6d616342 100644
--- a/lib/stm32/l1/Makefile
+++ b/lib/stm32/l1/Makefile
@@ -37,7 +37,7 @@ OBJS += adc.o adc_common_v1.o adc_common_v1_multi.o
 OBJS += flash.o
 OBJS += crc_common_all.o
 OBJS += dac_common_all.o
-OBJS += desig_common_all.o desig_common_v1.o
+OBJS += desig_common_all.o desig.o
 OBJS += dma_common_l1f013.o
 OBJS += exti_common_all.o
 OBJS += flash_common_all.o flash_common_l01.o
diff --git a/lib/stm32/l1/desig.c b/lib/stm32/l1/desig.c
new file mode 100644
index 00000000..0bdf98b4
--- /dev/null
+++ b/lib/stm32/l1/desig.c
@@ -0,0 +1,65 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2020 Karl Palsson <karlp@tweak.net.au>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <libopencm3/cm3/assert.h>
+#include <libopencm3/stm32/dbgmcu.h>
+#include <libopencm3/stm32/desig.h>
+
+uint16_t desig_get_flash_size(void)
+{
+	uint32_t device_id = DBGMCU_IDCODE & DBGMCU_IDCODE_DEV_ID_MASK;
+	switch (device_id) {
+	case 0x416:
+	case 0x429:
+		return *(uint32_t*)DESIG_FLASH_SIZE_BASE_CAT12;
+	case 0x427:
+	case 0x436:
+	case 0x437:
+		return *(uint32_t*)DESIG_FLASH_SIZE_BASE_CAT3456;
+	}
+
+	cm3_assert_not_reached();
+}
+
+void desig_get_unique_id(uint32_t *result)
+{
+	uint32_t device_id = DBGMCU_IDCODE & DBGMCU_IDCODE_DEV_ID_MASK;
+	uint32_t* uid_base = 0;
+	switch (device_id) {
+	case 0x416:
+	case 0x429:
+		uid_base = (uint32_t*)DESIG_UNIQUE_ID_BASE_CAT12;
+		break;
+	case 0x427:
+	case 0x436:
+	case 0x437:
+		uid_base = (uint32_t*)DESIG_UNIQUE_ID_BASE_CAT3456;
+		break;
+	}
+
+	if (!uid_base) {
+		/* We don't know the address for this device. Hang here to help debugging. */
+		cm3_assert_not_reached();
+	}
+
+	/* yes, careful with offsets here */
+	result[0] = uid_base[5];
+	result[1] = uid_base[1];
+	result[2] = uid_base[0];
+}