diff --git a/ports/nrf/common-hal/busio/I2C.c b/ports/nrf/common-hal/busio/I2C.c
index 8ac76c304a..ad789c8c18 100644
--- a/ports/nrf/common-hal/busio/I2C.c
+++ b/ports/nrf/common-hal/busio/I2C.c
@@ -34,8 +34,27 @@
 #include "nrfx_twim.h"
 #include "nrf_gpio.h"
 
+#include "nrfx_spim.h"
+#include "nrf_gpio.h"
+
+STATIC twim_peripheral_t twim_peripherals[] = {
+#if NRFX_CHECK(NRFX_TWIM0_ENABLED)
+    // SPIM0 and TWIM0 share an address.
+    { .twim = NRFX_TWIM_INSTANCE(0),
+      .in_use = false,
+      .max_xfer_size = TWIM0_EASYDMA_MAXCNT_SIZE,
+    },
+#endif
+#if NRFX_CHECK(NRFX_TWIM1_ENABLED)
+    // SPIM1 and TWIM1 share an address.
+    { .twim = NRFX_TWIM_INSTANCE(1),
+      .in_use = false,
+      .max_xfer_size = TWIM1_EASYDMA_MAXCNT_SIZE,
+    },
+#endif
+};
+
 #define INST_NO 0
-#define MAX_XFER_SIZE ((1U << NRFX_CONCAT_3(TWIM, INST_NO, _EASYDMA_MAXCNT_SIZE)) - 1)
 
 static uint8_t twi_error_to_mp(const nrfx_err_t err) {
     switch (err) {
@@ -54,11 +73,23 @@ static uint8_t twi_error_to_mp(const nrfx_err_t err) {
 }
 
 void common_hal_busio_i2c_construct(busio_i2c_obj_t *self, const mcu_pin_obj_t *scl, const mcu_pin_obj_t *sda, uint32_t frequency, uint32_t timeout) {
-    if (scl->number == sda->number)
+    if (scl->number == sda->number) {
         mp_raise_ValueError(translate("Invalid pins"));
+    }
 
-    const nrfx_twim_t instance = NRFX_TWIM_INSTANCE(INST_NO);
-    self->twim = instance;
+    // Find a free instance.
+    self->twim_peripheral = NULL;
+    for (size_t i = 0 ; i < MP_ARRAY_SIZE(twim_peripherals); i++) {
+        if (!twim_peripherals[i].in_use) {
+            self->twim_peripheral = &twim_peripherals[i];
+            self->twim_peripheral->in_use = true;
+            break;
+        }
+    }
+
+    if (self->twim_peripheral == NULL) {
+        mp_raise_ValueError(translate("All I2C peripherals are in use"));
+    }
 
     nrfx_twim_config_t config = NRFX_TWIM_DEFAULT_CONFIG;
     config.scl = scl->number;
@@ -76,12 +107,12 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self, const mcu_pin_obj_t *
     claim_pin(sda);
     claim_pin(scl);
 
-    nrfx_err_t err = nrfx_twim_init(&self->twim, &config, NULL, NULL);
+    nrfx_err_t err = nrfx_twim_init(&self->twim_peripheral->twim, &config, NULL, NULL);
 
     // A soft reset doesn't uninit the driver so we might end up with a invalid state
     if (err == NRFX_ERROR_INVALID_STATE) {
-        nrfx_twim_uninit(&self->twim);
-        err = nrfx_twim_init(&self->twim, &config, NULL, NULL);
+        nrfx_twim_uninit(&self->twim_peripheral->twim);
+        err = nrfx_twim_init(&self->twim_peripheral->twim, &config, NULL, NULL);
     }
 
     if (err != NRFX_SUCCESS) {
@@ -99,20 +130,22 @@ void common_hal_busio_i2c_deinit(busio_i2c_obj_t *self) {
     if (common_hal_busio_i2c_deinited(self))
         return;
 
-    nrfx_twim_uninit(&self->twim);
+    nrfx_twim_uninit(&self->twim_peripheral->twim);
 
     reset_pin_number(self->sda_pin_number);
     reset_pin_number(self->scl_pin_number);
     self->sda_pin_number = NO_PIN;
     self->scl_pin_number = NO_PIN;
+
+    self->twim_peripheral->in_use = false;
 }
 
 // nrfx_twim_tx doesn't support 0-length data so we fall back to the hal API
 bool common_hal_busio_i2c_probe(busio_i2c_obj_t *self, uint8_t addr) {
-    NRF_TWIM_Type *reg = self->twim.p_twim;
+    NRF_TWIM_Type *reg = self->twim_peripheral->twim.p_twim;
     bool found = true;
 
-    nrfx_twim_enable(&self->twim);
+    nrfx_twim_enable(&self->twim_peripheral->twim);
 
     nrf_twim_address_set(reg, addr);
     nrf_twim_tx_buffer_set(reg, NULL, 0);
@@ -135,19 +168,19 @@ bool common_hal_busio_i2c_probe(busio_i2c_obj_t *self, uint8_t addr) {
         found = false;
     }
 
-    nrfx_twim_disable(&self->twim);
+    nrfx_twim_disable(&self->twim_peripheral->twim);
 
     return found;
 }
 
 bool common_hal_busio_i2c_try_lock(busio_i2c_obj_t *self) {
     bool grabbed_lock = false;
-//    CRITICAL_SECTION_ENTER()
-        if (!self->has_lock) {
-            grabbed_lock = true;
-            self->has_lock = true;
-        }
-//    CRITICAL_SECTION_LEAVE();
+    // NRFX_CRITICAL_SECTION_ENTER();
+    if (!self->has_lock) {
+        grabbed_lock = true;
+        self->has_lock = true;
+    }
+    // NRFX_CRITICAL_SECTION_EXIT();
     return grabbed_lock;
 }
 
@@ -163,22 +196,23 @@ uint8_t common_hal_busio_i2c_write(busio_i2c_obj_t *self, uint16_t addr, const u
     if(len == 0)
         return common_hal_busio_i2c_probe(self, addr) ? 0 : MP_ENODEV;
 
-    const uint32_t parts = len / MAX_XFER_SIZE;
-    const uint32_t remainder = len % MAX_XFER_SIZE;
+    const uint32_t max_xfer_size = self->twim_peripheral->max_xfer_size;
+    const uint32_t parts = len / max_xfer_size;
+    const uint32_t remainder = len % max_xfer_size;
     nrfx_err_t err = NRFX_SUCCESS;
 
-    nrfx_twim_enable(&self->twim);
+    nrfx_twim_enable(&self->twim_peripheral->twim);
 
     for (uint32_t i = 0; i < parts; ++i) {
-        err = nrfx_twim_tx(&self->twim, addr, data + i * MAX_XFER_SIZE, MAX_XFER_SIZE, !stopBit);
+        err = nrfx_twim_tx(&self->twim_peripheral->twim, addr, data + i * max_xfer_size, max_xfer_size, !stopBit);
         if (err != NRFX_SUCCESS)
             break;
     }
 
     if ((remainder > 0) && (err == NRFX_SUCCESS))
-        err = nrfx_twim_tx(&self->twim, addr, data + parts * MAX_XFER_SIZE, remainder, !stopBit);
+        err = nrfx_twim_tx(&self->twim_peripheral->twim, addr, data + parts * max_xfer_size, remainder, !stopBit);
 
-    nrfx_twim_disable(&self->twim);
+    nrfx_twim_disable(&self->twim_peripheral->twim);
 
     return twi_error_to_mp(err);
 }
@@ -187,22 +221,23 @@ uint8_t common_hal_busio_i2c_read(busio_i2c_obj_t *self, uint16_t addr, uint8_t
     if(len == 0)
         return 0;
 
-    const uint32_t parts = len / MAX_XFER_SIZE;
-    const uint32_t remainder = len % MAX_XFER_SIZE;
+    const uint32_t max_xfer_size = self->twim_peripheral->max_xfer_size;
+    const uint32_t parts = len / max_xfer_size;
+    const uint32_t remainder = len % max_xfer_size;
     nrfx_err_t err = NRFX_SUCCESS;
 
-    nrfx_twim_enable(&self->twim);
+    nrfx_twim_enable(&self->twim_peripheral->twim);
 
     for (uint32_t i = 0; i < parts; ++i) {
-        err = nrfx_twim_rx(&self->twim, addr, data + i * MAX_XFER_SIZE, MAX_XFER_SIZE);
+        err = nrfx_twim_rx(&self->twim_peripheral->twim, addr, data + i * max_xfer_size, max_xfer_size);
         if (err != NRFX_SUCCESS)
             break;
     }
 
     if ((remainder > 0) && (err == NRFX_SUCCESS))
-        err = nrfx_twim_rx(&self->twim, addr, data + parts * MAX_XFER_SIZE, remainder);
+        err = nrfx_twim_rx(&self->twim_peripheral->twim, addr, data + parts * max_xfer_size, remainder);
 
-    nrfx_twim_disable(&self->twim);
+    nrfx_twim_disable(&self->twim_peripheral->twim);
 
     return twi_error_to_mp(err);
 }
diff --git a/ports/nrf/common-hal/busio/I2C.h b/ports/nrf/common-hal/busio/I2C.h
index a133ff071a..5606f46b0e 100644
--- a/ports/nrf/common-hal/busio/I2C.h
+++ b/ports/nrf/common-hal/busio/I2C.h
@@ -32,8 +32,14 @@
 #include "py/obj.h"
 
 typedef struct {
-    mp_obj_base_t base;
     nrfx_twim_t twim;
+    bool in_use;
+    uint8_t max_xfer_size;
+} twim_peripheral_t;
+
+typedef struct {
+    mp_obj_base_t base;
+    twim_peripheral_t* twim_peripheral;
     bool has_lock;
     uint8_t scl_pin_number;
     uint8_t sda_pin_number;
diff --git a/ports/nrf/common-hal/busio/SPI.c b/ports/nrf/common-hal/busio/SPI.c
index 21f80ff101..6e7f33dc73 100644
--- a/ports/nrf/common-hal/busio/SPI.c
+++ b/ports/nrf/common-hal/busio/SPI.c
@@ -186,12 +186,12 @@ bool common_hal_busio_spi_configure(busio_spi_obj_t *self, uint32_t baudrate, ui
 
 bool common_hal_busio_spi_try_lock(busio_spi_obj_t *self) {
     bool grabbed_lock = false;
-//    CRITICAL_SECTION_ENTER()
-//        if (!self->has_lock) {
-            grabbed_lock = true;
-            self->has_lock = true;
-//        }
-//    CRITICAL_SECTION_LEAVE();
+    // NRFX_CRITICAL_SECTION_ENTER();
+    if (!self->has_lock) {
+        grabbed_lock = true;
+        self->has_lock = true;
+    }
+    // NRFX_CRITICAL_SECTION_EXIT();
     return grabbed_lock;
 }
 
diff --git a/ports/nrf/nrfx_config.h b/ports/nrf/nrfx_config.h
index 36f2665a51..cc4d193277 100644
--- a/ports/nrf/nrfx_config.h
+++ b/ports/nrf/nrfx_config.h
@@ -5,11 +5,27 @@
 #define NRFX_POWER_ENABLED 1
 #define NRFX_POWER_CONFIG_IRQ_PRIORITY 7
 
+// Turn on nrfx supported workarounds for errata in Rev1/Rev2 of nRF52832
+#ifdef NRF52832_XXAA
+    #define NRFX_SPIS_NRF52_ANOMALY_109_WORKAROUND_ENABLED 1
+#endif
+
+// Turn on nrfx supported workarounds for errata in Rev1 of nRF52840
+#ifdef NRF52840_XXAA
+    #define NRFX_SPIM3_NRF52840_ANOMALY_198_WORKAROUND_ENABLED 1
+#endif
+
 // SPI
 #define NRFX_SPIM_ENABLED 1
 
-#define NRFX_SPIM0_ENABLED 1
-#define NRFX_SPIM1_ENABLED 1
+// TWIM0 and TWIM1 are the same peripherals as SPIM0 and SPIM1.
+// The IRQ handlers for these peripherals are set up at compile time,
+// so out of the box TWIM0/SPIM0 and TWIM1/SPIM1 cannot be shared
+// between common-hal/busio/I2C.c and SPI.c.
+// We could write an interrupt handler that checks whether it's
+// being used for SPI or I2C, but perhaps two I2C's and 1-2 SPI's are good enough for now.
+
+// Enable SPIM2 and SPIM3 (if available)
 #define NRFX_SPIM2_ENABLED 1
 #ifdef NRF52840_XXAA
     #define NRFX_SPIM3_ENABLED 1
@@ -19,7 +35,7 @@
 #define NRFX_SPIM_DEFAULT_CONFIG_IRQ_PRIORITY 7
 #define NRFX_SPIM_MISO_PULL_CFG 1
 
-// TWI aka. I2C
+// TWI aka. I2C; enable TWIM0 and TWIM1 (no conflict with SPIM choices)
 #define NRFX_TWIM_ENABLED 1
 #define NRFX_TWIM0_ENABLED 1
 #define NRFX_TWIM1_ENABLED 1