diff --git a/ports/samd/machine_i2c.c b/ports/samd/machine_i2c.c
index 0a8f5b94db..d943b6b2f4 100644
--- a/ports/samd/machine_i2c.c
+++ b/ports/samd/machine_i2c.c
@@ -69,7 +69,6 @@ typedef struct _machine_i2c_obj_t {
 } machine_i2c_obj_t;
 
 extern Sercom *sercom_instance[];
-extern void *sercom_table[SERCOM_INST_NUM];
 
 STATIC void i2c_send_command(Sercom *i2c, uint8_t command) {
     i2c->I2CM.CTRLB.bit.CMD = command;
@@ -79,7 +78,7 @@ STATIC void i2c_send_command(Sercom *i2c, uint8_t command) {
 
 void common_i2c_irq_handler(int i2c_id) {
     // handle Sercom I2C IRQ
-    machine_i2c_obj_t *self = sercom_table[i2c_id];
+    machine_i2c_obj_t *self = MP_STATE_PORT(sercom_table[i2c_id]);
     // Handle IRQ
     if (self != NULL) {
         Sercom *i2c = self->instance;
@@ -159,7 +158,7 @@ mp_obj_t machine_i2c_make_new(const mp_obj_type_t *type, size_t n_args, size_t n
     if (sda_pad_config.pad_nr != 0 || scl_pad_config.pad_nr != 1) {
         mp_raise_ValueError(MP_ERROR_TEXT("invalid pin for sda or scl"));
     }
-    sercom_table[self->id] = self;
+    MP_STATE_PORT(sercom_table[self->id]) = self;
     self->freq = args[ARG_freq].u_int;
 
     // Configure the Pin mux.
diff --git a/ports/samd/machine_spi.c b/ports/samd/machine_spi.c
index d4c7a05bb6..4ffc7095cc 100644
--- a/ports/samd/machine_spi.c
+++ b/ports/samd/machine_spi.c
@@ -57,11 +57,11 @@ typedef struct _machine_spi_obj_t {
 } machine_spi_obj_t;
 
 extern Sercom *sercom_instance[];
-void *sercom_table[SERCOM_INST_NUM] = {};
+MP_REGISTER_ROOT_POINTER(void *sercom_table[SERCOM_INST_NUM]);
 
 void common_spi_irq_handler(int spi_id) {
     // handle Sercom IRQ RXC
-    machine_spi_obj_t *self = sercom_table[spi_id];
+    machine_spi_obj_t *self = MP_STATE_PORT(sercom_table[spi_id]);
     // Handle IRQ
     if (self != NULL) {
         Sercom *spi = sercom_instance[self->id];
@@ -246,7 +246,7 @@ STATIC mp_obj_t machine_spi_make_new(const mp_obj_type_t *type, size_t n_args, s
     self->sck = 0xff;
 
     self->new = true;
-    sercom_table[spi_id] = self;
+    MP_STATE_PORT(sercom_table[spi_id]) = self;
 
     mp_map_t kw_args;
     mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
@@ -261,7 +261,7 @@ STATIC void machine_sercom_deinit(mp_obj_base_t *self_in) {
     spi->SPI.INTENCLR.reg = 0xff;
     sercom_enable(spi, 0);
     // clear table entry of spi
-    sercom_table[self->id] = NULL;
+    MP_STATE_PORT(sercom_table[self->id]) = NULL;
 }
 
 void sercom_deinit_all(void) {
@@ -270,7 +270,7 @@ void sercom_deinit_all(void) {
         spi->SPI.INTENCLR.reg = 0xff;
         sercom_register_irq(i, NULL);
         sercom_enable(spi, 0);
-        sercom_table[i] = NULL;
+        MP_STATE_PORT(sercom_table[i]) = NULL;
     }
 }
 
diff --git a/ports/samd/machine_uart.c b/ports/samd/machine_uart.c
index 2526b45093..4b8fa3b60d 100644
--- a/ports/samd/machine_uart.c
+++ b/ports/samd/machine_uart.c
@@ -59,7 +59,6 @@ typedef struct _machine_uart_obj_t {
 } machine_uart_obj_t;
 
 Sercom *sercom_instance[] = SERCOM_INSTS;
-extern void *sercom_table[SERCOM_INST_NUM];
 
 STATIC const char *_parity_name[] = {"None", "", "0", "1"};  // Is defined as 0, 2, 3
 
@@ -82,7 +81,7 @@ STATIC void uart_drain_rx_fifo(machine_uart_obj_t *self, Sercom *uart) {
 }
 
 void common_uart_irq_handler(int uart_id) {
-    machine_uart_obj_t *self = sercom_table[uart_id];
+    machine_uart_obj_t *self = MP_STATE_PORT(sercom_table[uart_id]);
     // Handle IRQ
     if (self != NULL) {
         Sercom *uart = sercom_instance[self->id];
@@ -333,7 +332,7 @@ STATIC mp_obj_t machine_uart_make_new(const mp_obj_type_t *type, size_t n_args,
     self->tx = 0xff;
     self->rx = 0xff;
     self->new = true;
-    sercom_table[uart_id] = self;
+    MP_STATE_PORT(sercom_table[uart_id]) = self;
 
     mp_map_t kw_args;
     mp_map_init_fixed_table(&kw_args, n_kw, args + n_args);
@@ -352,7 +351,7 @@ STATIC mp_obj_t machine_uart_deinit(mp_obj_t self_in) {
     // Disable interrupts
     uart->USART.INTENCLR.reg = 0xff;
     // clear table entry of uart
-    sercom_table[self->id] = NULL;
+    MP_STATE_PORT(sercom_table[self->id]) = NULL;
     MP_STATE_PORT(samd_uart_rx_buffer[self->id]) = NULL;
     #if MICROPY_HW_UART_TXBUF
     MP_STATE_PORT(samd_uart_tx_buffer[self->id]) = NULL;