diff --git a/ports/stm32/spi.c b/ports/stm32/spi.c
index d090181483..411083bf29 100644
--- a/ports/stm32/spi.c
+++ b/ports/stm32/spi.c
@@ -563,3 +563,34 @@ const spi_t *spi_from_mp_obj(mp_obj_t o) {
         mp_raise_TypeError("expecting an SPI object");
     }
 }
+
+/******************************************************************************/
+// Implementation of low-level SPI C protocol
+
+STATIC int spi_proto_ioctl(void *self_in, uint32_t cmd) {
+    spi_proto_cfg_t *self = (spi_proto_cfg_t*)self_in;
+
+    switch (cmd) {
+        case MP_SPI_IOCTL_INIT:
+            spi_set_params(self->spi, 0xffffffff, self->baudrate,
+                self->polarity, self->phase, self->bits, self->firstbit);
+            spi_init(self->spi, false);
+            break;
+
+        case MP_SPI_IOCTL_DEINIT:
+            spi_deinit(self->spi);
+            break;
+    }
+
+    return 0;
+}
+
+STATIC void spi_proto_transfer(void *self_in, size_t len, const uint8_t *src, uint8_t *dest) {
+    spi_proto_cfg_t *self = (spi_proto_cfg_t*)self_in;
+    spi_transfer(self->spi, len, src, dest, SPI_TRANSFER_TIMEOUT(len));
+}
+
+const mp_spi_proto_t spi_proto = {
+    .ioctl = spi_proto_ioctl,
+    .transfer = spi_proto_transfer,
+};
diff --git a/ports/stm32/spi.h b/ports/stm32/spi.h
index 41e7a47e78..885fb0bd6f 100644
--- a/ports/stm32/spi.h
+++ b/ports/stm32/spi.h
@@ -26,6 +26,7 @@
 #ifndef MICROPY_INCLUDED_STM32_SPI_H
 #define MICROPY_INCLUDED_STM32_SPI_H
 
+#include "drivers/bus/spi.h"
 #include "dma.h"
 
 typedef struct _spi_t {
@@ -34,6 +35,15 @@ typedef struct _spi_t {
     const dma_descr_t *rx_dma_descr;
 } spi_t;
 
+typedef struct _spi_proto_cfg_t {
+    const spi_t *spi;
+    uint32_t baudrate;
+    uint8_t polarity;
+    uint8_t phase;
+    uint8_t bits;
+    uint8_t firstbit;
+} spi_proto_cfg_t;
+
 typedef struct _pyb_spi_obj_t {
     mp_obj_base_t base;
     const spi_t *spi;
@@ -53,6 +63,7 @@ extern SPI_HandleTypeDef SPIHandle6;
 
 extern const spi_t spi_obj[6];
 
+extern const mp_spi_proto_t spi_proto;
 extern const mp_obj_type_t pyb_spi_type;
 extern const mp_obj_type_t machine_soft_spi_type;
 extern const mp_obj_type_t machine_hard_spi_type;