diff --git a/stmhal/accel.c b/stmhal/accel.c
index 827e9177a0..2e3504b06e 100644
--- a/stmhal/accel.c
+++ b/stmhal/accel.c
@@ -76,9 +76,9 @@ STATIC void accel_start(void) {
 
     // turn off AVDD, wait 30ms, turn on AVDD, wait 30ms again
     mp_hal_pin_low(&MICROPY_HW_MMA_AVDD_PIN); // turn off
-    HAL_Delay(30);
+    mp_hal_delay_ms(30);
     mp_hal_pin_high(&MICROPY_HW_MMA_AVDD_PIN); // turn on
-    HAL_Delay(30);
+    mp_hal_delay_ms(30);
 
     HAL_StatusTypeDef status;
 
@@ -98,7 +98,7 @@ STATIC void accel_start(void) {
     status = HAL_I2C_Mem_Write(&I2CHandle1, MMA_ADDR, MMA_REG_MODE, I2C_MEMADD_SIZE_8BIT, data, 1, 200);
 
     // wait for MMA to become active
-    HAL_Delay(30);
+    mp_hal_delay_ms(30);
 }
 
 /******************************************************************************/
diff --git a/stmhal/i2c.c b/stmhal/i2c.c
index 29c350d22f..412a8e3638 100644
--- a/stmhal/i2c.c
+++ b/stmhal/i2c.c
@@ -346,7 +346,7 @@ STATIC void i2c_reset_after_error(I2C_HandleTypeDef *i2c) {
             // stop bit was generated and bus is back to normal
             return;
         }
-        HAL_Delay(1);
+        mp_hal_delay_ms(1);
     }
     // bus was/is busy, need to reset the peripheral to get it to work again
     i2c_deinit(i2c);
diff --git a/stmhal/lcd.c b/stmhal/lcd.c
index e73b6e16d3..cde6c36f67 100644
--- a/stmhal/lcd.c
+++ b/stmhal/lcd.c
@@ -274,11 +274,11 @@ STATIC mp_obj_t pyb_lcd_make_new(const mp_obj_type_t *type, size_t n_args, size_
     mp_hal_pin_output(lcd->pin_bl);
 
     // init the LCD
-    HAL_Delay(1); // wait a bit
+    mp_hal_delay_ms(1); // wait a bit
     mp_hal_pin_low(lcd->pin_rst); // RST=0; reset
-    HAL_Delay(1); // wait for reset; 2us min
+    mp_hal_delay_ms(1); // wait for reset; 2us min
     mp_hal_pin_high(lcd->pin_rst); // RST=1; enable
-    HAL_Delay(1); // wait for reset; 2us min
+    mp_hal_delay_ms(1); // wait for reset; 2us min
     lcd_out(lcd, LCD_INSTR, 0xa0); // ADC select, normal
     lcd_out(lcd, LCD_INSTR, 0xc0); // common output mode select, normal (this flips the display)
     lcd_out(lcd, LCD_INSTR, 0xa2); // LCD bias set, 1/9 bias
diff --git a/stmhal/led.c b/stmhal/led.c
index 357aed4074..be98aa4a4d 100644
--- a/stmhal/led.c
+++ b/stmhal/led.c
@@ -275,7 +275,7 @@ void led_debug(int n, int delay) {
     led_state(2, n & 2);
     led_state(3, n & 4);
     led_state(4, n & 8);
-    HAL_Delay(delay);
+    mp_hal_delay_ms(delay);
 }
 
 /******************************************************************************/
diff --git a/stmhal/main.c b/stmhal/main.c
index c6d482f3ce..e07f6cf8c5 100644
--- a/stmhal/main.c
+++ b/stmhal/main.c
@@ -71,10 +71,10 @@ void flash_error(int n) {
     for (int i = 0; i < n; i++) {
         led_state(PYB_LED_RED, 1);
         led_state(PYB_LED_GREEN, 0);
-        HAL_Delay(250);
+        mp_hal_delay_ms(250);
         led_state(PYB_LED_RED, 0);
         led_state(PYB_LED_GREEN, 1);
-        HAL_Delay(250);
+        mp_hal_delay_ms(250);
     }
     led_state(PYB_LED_GREEN, 0);
 }
@@ -349,7 +349,7 @@ STATIC uint update_reset_mode(uint reset_mode) {
             if (!switch_get()) {
                 break;
             }
-            HAL_Delay(20);
+            mp_hal_delay_ms(20);
             if (i % 30 == 29) {
                 if (++reset_mode > 3) {
                     reset_mode = 1;
@@ -364,13 +364,13 @@ STATIC uint update_reset_mode(uint reset_mode) {
             led_state(2, 0);
             led_state(3, 0);
             led_state(4, 0);
-            HAL_Delay(50);
+            mp_hal_delay_ms(50);
             led_state(2, reset_mode & 1);
             led_state(3, reset_mode & 2);
             led_state(4, reset_mode & 4);
-            HAL_Delay(50);
+            mp_hal_delay_ms(50);
         }
-        HAL_Delay(400);
+        mp_hal_delay_ms(400);
 
 #elif defined(MICROPY_HW_LED1)
 
@@ -383,11 +383,11 @@ STATIC uint update_reset_mode(uint reset_mode) {
                     break;
                 }
                 led_state(1, 1);
-                HAL_Delay(100);
+                mp_hal_delay_ms(100);
                 led_state(1, 0);
-                HAL_Delay(200);
+                mp_hal_delay_ms(200);
             }
-            HAL_Delay(400);
+            mp_hal_delay_ms(400);
             if (!switch_get()) {
                 break;
             }
@@ -399,11 +399,11 @@ STATIC uint update_reset_mode(uint reset_mode) {
         for (uint i = 0; i < 2; i++) {
             for (uint j = 0; j < reset_mode; j++) {
                 led_state(1, 1);
-                HAL_Delay(100);
+                mp_hal_delay_ms(100);
                 led_state(1, 0);
-                HAL_Delay(200);
+                mp_hal_delay_ms(200);
             }
-            HAL_Delay(400);
+            mp_hal_delay_ms(400);
         }
 #else
 #error Need a reset mode update method
diff --git a/stmhal/modmachine.c b/stmhal/modmachine.c
index 16c50079d1..d615a0f2b7 100644
--- a/stmhal/modmachine.c
+++ b/stmhal/modmachine.c
@@ -324,7 +324,7 @@ STATIC mp_obj_t machine_freq(mp_uint_t n_args, const mp_obj_t *args) {
         //printf("%lu %lu %lu %lu %lu\n", sysclk_source, m, n, p, q);
 
         // let the USB CDC have a chance to process before we change the clock
-        HAL_Delay(5);
+        mp_hal_delay_ms(5);
 
         // desired system clock source is in sysclk_source
         RCC_ClkInitTypeDef RCC_ClkInitStruct;
diff --git a/stmhal/modnwcc3k.c b/stmhal/modnwcc3k.c
index 19aeabf5ce..753ab7528e 100644
--- a/stmhal/modnwcc3k.c
+++ b/stmhal/modnwcc3k.c
@@ -120,7 +120,7 @@ STATIC int cc3k_gethostbyname(mp_obj_t nic, const char *name, mp_uint_t len, uin
         if (retry == 0 || CC3000_EXPORT(errno) != -95) {
             return CC3000_EXPORT(errno);
         }
-        HAL_Delay(50);
+        mp_hal_delay_ms(50);
     }
 
     if (ip == 0) {
diff --git a/stmhal/modnwwiznet5k.c b/stmhal/modnwwiznet5k.c
index 04d37cceef..e3d5c6370c 100644
--- a/stmhal/modnwwiznet5k.c
+++ b/stmhal/modnwwiznet5k.c
@@ -202,7 +202,7 @@ STATIC int wiznet5k_socket_accept(mod_network_socket_obj_t *socket, mod_network_
             *_errno = MP_ENOTCONN; // ??
             return -1;
         }
-        HAL_Delay(1);
+        mp_hal_delay_ms(1);
     }
 }
 
@@ -348,9 +348,9 @@ STATIC mp_obj_t wiznet5k_make_new(const mp_obj_type_t *type, size_t n_args, size
     mp_hal_pin_output(wiznet5k_obj.rst);
 
     mp_hal_pin_low(wiznet5k_obj.rst);
-    HAL_Delay(1); // datasheet says 2us
+    mp_hal_delay_ms(1); // datasheet says 2us
     mp_hal_pin_high(wiznet5k_obj.rst);
-    HAL_Delay(160); // datasheet says 150ms
+    mp_hal_delay_ms(160); // datasheet says 150ms
 
     reg_wizchip_cris_cbfunc(wiz_cris_enter, wiz_cris_exit);
     reg_wizchip_cs_cbfunc(wiz_cs_select, wiz_cs_deselect);
@@ -371,7 +371,7 @@ STATIC mp_obj_t wiznet5k_make_new(const mp_obj_type_t *type, size_t n_args, size
     ctlnetwork(CN_SET_NETINFO, (void*)&netinfo);
 
     // seems we need a small delay after init
-    HAL_Delay(250);
+    mp_hal_delay_ms(250);
 
     // register with network module
     mod_network_register_nic(&wiznet5k_obj);
diff --git a/stmhal/sdcard.c b/stmhal/sdcard.c
index 6e9c46df54..c93b98b51e 100644
--- a/stmhal/sdcard.c
+++ b/stmhal/sdcard.c
@@ -145,7 +145,7 @@ bool sdcard_power_on(void) {
         if (retry == 0) {
             goto error;
         }
-        HAL_Delay(50);
+        mp_hal_delay_ms(50);
     }
 
     // configure the SD bus width for wide operation