diff --git a/ports/stm32/machine_uart.c b/ports/stm32/machine_uart.c
index fa686d0605..e282e32d56 100644
--- a/ports/stm32/machine_uart.c
+++ b/ports/stm32/machine_uart.c
@@ -223,25 +223,18 @@ STATIC mp_obj_t pyb_uart_init_helper(pyb_uart_obj_t *self, size_t n_args, const
         }
         self->char_width = CHAR_WIDTH_8BIT;
     }
-    self->read_buf_head = 0;
-    self->read_buf_tail = 0;
     if (args.rxbuf.u_int >= 0) {
         // rxbuf overrides legacy read_buf_len
         args.read_buf_len.u_int = args.rxbuf.u_int;
     }
     if (args.read_buf_len.u_int <= 0) {
         // no read buffer
-        self->read_buf_len = 0;
-        self->read_buf = NULL;
-        HAL_NVIC_DisableIRQ(self->irqn);
-        __HAL_UART_DISABLE_IT(&self->uart, UART_IT_RXNE);
+        uart_set_rxbuf(self, 0, NULL);
     } else {
         // read buffer using interrupts
-        self->read_buf_len = args.read_buf_len.u_int + 1; // +1 to adjust for usable length of buffer
-        self->read_buf = m_new(byte, self->read_buf_len << self->char_width);
-        __HAL_UART_ENABLE_IT(&self->uart, UART_IT_RXNE);
-        NVIC_SetPriority(IRQn_NONNEG(self->irqn), IRQ_PRI_UART);
-        HAL_NVIC_EnableIRQ(self->irqn);
+        size_t len = args.read_buf_len.u_int + 1; // +1 to adjust for usable length of buffer
+        uint8_t *buf = m_new(byte, len << self->char_width);
+        uart_set_rxbuf(self, len, buf);
     }
 
     // compute actual baudrate that was configured
diff --git a/ports/stm32/uart.c b/ports/stm32/uart.c
index ba9cce5074..c29d393666 100644
--- a/ports/stm32/uart.c
+++ b/ports/stm32/uart.c
@@ -302,6 +302,21 @@ bool uart_init2(pyb_uart_obj_t *uart_obj) {
     return true;
 }
 
+void uart_set_rxbuf(pyb_uart_obj_t *self, size_t len, void *buf) {
+    self->read_buf_head = 0;
+    self->read_buf_tail = 0;
+    self->read_buf_len = len;
+    self->read_buf = buf;
+    if (len == 0) {
+        HAL_NVIC_DisableIRQ(self->irqn);
+        __HAL_UART_DISABLE_IT(&self->uart, UART_IT_RXNE);
+    } else {
+        __HAL_UART_ENABLE_IT(&self->uart, UART_IT_RXNE);
+        NVIC_SetPriority(IRQn_NONNEG(self->irqn), IRQ_PRI_UART);
+        HAL_NVIC_EnableIRQ(self->irqn);
+    }
+}
+
 void uart_deinit(pyb_uart_obj_t *self) {
     self->is_enabled = false;
     UART_HandleTypeDef *uart = &self->uart;
diff --git a/ports/stm32/uart.h b/ports/stm32/uart.h
index c69b87491b..fb7768db22 100644
--- a/ports/stm32/uart.h
+++ b/ports/stm32/uart.h
@@ -64,6 +64,7 @@ void uart_init0(void);
 void uart_deinit_all(void);
 bool uart_exists(int uart_id);
 bool uart_init2(pyb_uart_obj_t *uart_obj);
+void uart_set_rxbuf(pyb_uart_obj_t *self, size_t len, void *buf);
 void uart_deinit(pyb_uart_obj_t *uart_obj);
 void uart_irq_handler(mp_uint_t uart_id);