stm32/uart: Add support for LPUART1 on L0, L4, H7 and WB MCUs.

Add LPUART1 as a standard UART.  No low power features are supported, yet.
LPUART1 is enabled as the next available UART after the standard U(S)ARTs:

    STM32WB:      LPUART1 = UART(2)
    STM32L0:      LPUART1 = UART(6)
    STM32L4:      LPUART1 = UART(6)
    STM32H7:      LPUART1 = UART(9)

On all ports: LPUART1 = machine.UART('LP1')

LPUART1 is enabled by defining MICROPY_HW_LPUART1_TX and
MICROPY_HW_LPUART1_RX in mpconfigboard.h.
Signed-off-by: Chris Mason <c.mason@inchipdesign.com.au>

ports/stm32/boards/make-pins.py

@@ -14,6 +14,7 @@ SUPPORTED_FN = {
     "I2S": ["CK", "MCK", "SD", "WS", "EXTSD"],
     "USART": ["RX", "TX", "CTS", "RTS", "CK"],
     "UART": ["RX", "TX", "CTS", "RTS"],
+    "LPUART": ["RX", "TX", "CTS", "RTS"],
     "SPI": ["NSS", "SCK", "MISO", "MOSI"],
     "SDMMC": ["CK", "CMD", "D0", "D1", "D2", "D3"],
     "CAN": ["TX", "RX"],
@@ -24,6 +25,7 @@ CONDITIONAL_VAR = {
     "I2S": "MICROPY_HW_ENABLE_I2S{num}",
     "SPI": "MICROPY_HW_SPI{num}_SCK",
     "UART": "MICROPY_HW_UART{num}_TX",
+    "LPUART": "MICROPY_HW_LPUART{num}_TX",
     "USART": "MICROPY_HW_UART{num}_TX",
     "SDMMC": "MICROPY_HW_SDMMC{num}_CK",
     "CAN": "MICROPY_HW_CAN{num}_TX",

ports/stm32/machine_uart.c

@@ -76,7 +76,14 @@
 STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     pyb_uart_obj_t *self = MP_OBJ_TO_PTR(self_in);
     if (!self->is_enabled) {
-        mp_printf(print, "UART(%u)", self->uart_id);
+        #ifdef LPUART1
+        if (self->uart_id == PYB_LPUART_1) {
+            mp_printf(print, "UART('LP1')");
+        } else
+        #endif
+        {
+            mp_printf(print, "UART(%u)", self->uart_id);
+        }
     } else {
         mp_int_t bits;
         uint32_t cr1 = self->uartx->CR1;
@@ -98,8 +105,16 @@ STATIC void pyb_uart_print(const mp_print_t *print, mp_obj_t self_in, mp_print_k
         if (cr1 & USART_CR1_PCE) {
             bits -= 1;
         }
-        mp_printf(print, "UART(%u, baudrate=%u, bits=%u, parity=",
-            self->uart_id, uart_get_baudrate(self), bits);
+        #ifdef LPUART1
+        if (self->uart_id == PYB_LPUART_1) {
+            mp_printf(print, "UART('LP1', baudrate=%u, bits=%u, parity=",
+                uart_get_baudrate(self), bits);
+        } else
+        #endif
+        {
+            mp_printf(print, "UART(%u, baudrate=%u, bits=%u, parity=",
+                self->uart_id, uart_get_baudrate(self), bits);
+        }
         if (!(cr1 & USART_CR1_PCE)) {
             mp_print_str(print, "None");
         } else if (!(cr1 & USART_CR1_PS)) {
@@ -335,6 +350,14 @@ STATIC mp_obj_t pyb_uart_make_new(const mp_obj_type_t *type, size_t n_args, size
         } else if (strcmp(port, MICROPY_HW_UART10_NAME) == 0) {
             uart_id = PYB_UART_10;
         #endif
+        #ifdef MICROPY_HW_LPUART1_NAME
+        } else if (strcmp(port, MICROPY_HW_LPUART1_NAME) == 0) {
+            uart_id = PYB_LPUART_1;
+        #endif
+        #ifdef LPUART1
+        } else if (strcmp(port, "LP1") == 0 && uart_exists(PYB_LPUART_1)) {
+            uart_id = PYB_LPUART_1;
+        #endif
         } else {
             mp_raise_msg_varg(&mp_type_ValueError, MP_ERROR_TEXT("UART(%s) doesn't exist"), port);
         }

ports/stm32/mpconfigboard_common.h

@@ -181,6 +181,7 @@
 #define MICROPY_HW_MAX_I2C (2)
 #define MICROPY_HW_MAX_TIMER (17)
 #define MICROPY_HW_MAX_UART (8)
+#define MICROPY_HW_MAX_LPUART (0)
 
 // Configuration for STM32F4 series
 #elif defined(STM32F4)
@@ -200,6 +201,7 @@
 #else
 #define MICROPY_HW_MAX_UART (6)
 #endif
+#define MICROPY_HW_MAX_LPUART (0)
 
 // Configuration for STM32F7 series
 #elif defined(STM32F7)
@@ -214,6 +216,7 @@
 #define MICROPY_HW_MAX_I2C (4)
 #define MICROPY_HW_MAX_TIMER (17)
 #define MICROPY_HW_MAX_UART (8)
+#define MICROPY_HW_MAX_LPUART (0)
 
 // Configuration for STM32H7 series
 #elif defined(STM32H7)
@@ -223,6 +226,7 @@
 #define MICROPY_HW_MAX_I2C (4)
 #define MICROPY_HW_MAX_TIMER (17)
 #define MICROPY_HW_MAX_UART (8)
+#define MICROPY_HW_MAX_LPUART (1)
 
 // Configuration for STM32L0 series
 #elif defined(STM32L0)
@@ -232,6 +236,7 @@
 #define MICROPY_HW_MAX_I2C (3)
 #define MICROPY_HW_MAX_TIMER (22)
 #define MICROPY_HW_MAX_UART (5)
+#define MICROPY_HW_MAX_LPUART (1)
 
 // Configuration for STM32L4 series
 #elif defined(STM32L4)
@@ -240,7 +245,8 @@
 #define PYB_EXTI_NUM_VECTORS (23)
 #define MICROPY_HW_MAX_I2C (4)
 #define MICROPY_HW_MAX_TIMER (17)
-#define MICROPY_HW_MAX_UART (6)
+#define MICROPY_HW_MAX_UART (5)
+#define MICROPY_HW_MAX_LPUART (1)
 
 // Configuration for STM32WB series
 #elif defined(STM32WB)
@@ -250,6 +256,7 @@
 #define MICROPY_HW_MAX_I2C (3)
 #define MICROPY_HW_MAX_TIMER (17)
 #define MICROPY_HW_MAX_UART (1)
+#define MICROPY_HW_MAX_LPUART (1)
 
 #ifndef MICROPY_HW_STM32WB_FLASH_SYNCRONISATION
 #define MICROPY_HW_STM32WB_FLASH_SYNCRONISATION (1)

ports/stm32/mpconfigport.h

@@ -375,7 +375,7 @@ struct _mp_bluetooth_btstack_root_pointers_t;
     struct _pyb_uart_obj_t *pyb_stdio_uart; \
     \
     /* pointers to all UART objects (if they have been created) */ \
-    struct _pyb_uart_obj_t *pyb_uart_obj_all[MICROPY_HW_MAX_UART]; \
+    struct _pyb_uart_obj_t *pyb_uart_obj_all[MICROPY_HW_MAX_UART + MICROPY_HW_MAX_LPUART]; \
     \
     /* pointers to all CAN objects (if they have been created) */ \
     struct _pyb_can_obj_t *pyb_can_obj_all[MICROPY_HW_MAX_CAN]; \

ports/stm32/pin_defs_stm32.h

@@ -47,6 +47,7 @@ enum {
     AF_FN_I2C,
     AF_FN_USART,
     AF_FN_UART = AF_FN_USART,
+    AF_FN_LPUART,
     AF_FN_SPI,
     AF_FN_I2S,
     AF_FN_SDMMC,
@@ -77,6 +78,10 @@ enum {
     AF_PIN_TYPE_UART_RX  = AF_PIN_TYPE_USART_RX,
     AF_PIN_TYPE_UART_CTS = AF_PIN_TYPE_USART_CTS,
     AF_PIN_TYPE_UART_RTS = AF_PIN_TYPE_USART_RTS,
+    AF_PIN_TYPE_LPUART_TX  = AF_PIN_TYPE_USART_TX,
+    AF_PIN_TYPE_LPUART_RX  = AF_PIN_TYPE_USART_RX,
+    AF_PIN_TYPE_LPUART_CTS = AF_PIN_TYPE_USART_CTS,
+    AF_PIN_TYPE_LPUART_RTS = AF_PIN_TYPE_USART_RTS,
 
     AF_PIN_TYPE_SPI_MOSI = 0,
     AF_PIN_TYPE_SPI_MISO,

ports/stm32/stm32_it.c

@@ -742,11 +742,13 @@ void USART1_IRQHandler(void) {
     IRQ_EXIT(USART1_IRQn);
 }
 
+#if defined(USART2)
 void USART2_IRQHandler(void) {
     IRQ_ENTER(USART2_IRQn);
     uart_irq_handler(2);
     IRQ_EXIT(USART2_IRQn);
 }
+#endif
 
 #if defined(STM32F0)
 
@@ -772,29 +774,37 @@ void USART4_5_IRQHandler(void) {
 
 #else
 
+#if defined(USART3)
 void USART3_IRQHandler(void) {
     IRQ_ENTER(USART3_IRQn);
     uart_irq_handler(3);
     IRQ_EXIT(USART3_IRQn);
 }
+#endif
 
+#if defined(UART4)
 void UART4_IRQHandler(void) {
     IRQ_ENTER(UART4_IRQn);
     uart_irq_handler(4);
     IRQ_EXIT(UART4_IRQn);
 }
+#endif
 
+#if defined(UART5)
 void UART5_IRQHandler(void) {
     IRQ_ENTER(UART5_IRQn);
     uart_irq_handler(5);
     IRQ_EXIT(UART5_IRQn);
 }
+#endif
 
+#if defined(USART6)
 void USART6_IRQHandler(void) {
     IRQ_ENTER(USART6_IRQn);
     uart_irq_handler(6);
     IRQ_EXIT(USART6_IRQn);
 }
+#endif
 
 #if defined(UART7)
 void UART7_IRQHandler(void) {
@@ -830,6 +840,14 @@ void UART10_IRQHandler(void) {
 
 #endif
 
+#if defined(LPUART1)
+void LPUART1_IRQHandler(void) {
+    IRQ_ENTER(LPUART1_IRQn);
+    uart_irq_handler(PYB_LPUART_1);
+    IRQ_EXIT(LPUART1_IRQn);
+}
+#endif
+
 #if MICROPY_PY_PYB_LEGACY
 
 #if defined(MICROPY_HW_I2C1_SCL)

ports/stm32/uart.c

@@ -201,6 +201,11 @@ bool uart_exists(int uart_id) {
             return true;
         #endif
 
+        #if defined(MICROPY_HW_LPUART1_TX) && defined(MICROPY_HW_LPUART1_RX)
+        case PYB_LPUART_1:
+            return true;
+        #endif
+
         default:
             return false;
     }
@@ -211,6 +216,7 @@ bool uart_init(pyb_uart_obj_t *uart_obj,
     uint32_t baudrate, uint32_t bits, uint32_t parity, uint32_t stop, uint32_t flow) {
     USART_TypeDef *UARTx;
     IRQn_Type irqn;
+    uint8_t uart_fn = AF_FN_UART;
     int uart_unit;
 
     const pin_obj_t *pins[4] = {0};
@@ -406,6 +412,28 @@ bool uart_init(pyb_uart_obj_t *uart_obj,
             break;
         #endif
 
+        #if defined(MICROPY_HW_LPUART1_TX) && defined(MICROPY_HW_LPUART1_RX)
+        case PYB_LPUART_1:
+            uart_fn = AF_FN_LPUART;
+            uart_unit = 1;
+            UARTx = LPUART1;
+            irqn = LPUART1_IRQn;
+            pins[0] = MICROPY_HW_LPUART1_TX;
+            pins[1] = MICROPY_HW_LPUART1_RX;
+            #if defined(MICROPY_HW_LPUART1_RTS)
+            if (flow & UART_HWCONTROL_RTS) {
+                pins[2] = MICROPY_HW_LPUART1_RTS;
+            }
+            #endif
+            #if defined(MICROPY_HW_LPUART1_CTS)
+            if (flow & UART_HWCONTROL_CTS) {
+                pins[3] = MICROPY_HW_LPUART1_CTS;
+            }
+            #endif
+            __HAL_RCC_LPUART1_CLK_ENABLE();
+            break;
+        #endif
+
         default:
             // UART does not exist or is not configured for this board
             return false;
@@ -416,7 +444,7 @@ bool uart_init(pyb_uart_obj_t *uart_obj,
 
     for (uint i = 0; i < 4; i++) {
         if (pins[i] != NULL) {
-            bool ret = mp_hal_pin_config_alt(pins[i], mode, pull, AF_FN_UART, uart_unit);
+            bool ret = mp_hal_pin_config_alt(pins[i], mode, pull, uart_fn, uart_unit);
             if (!ret) {
                 return false;
             }
@@ -596,6 +624,13 @@ void uart_deinit(pyb_uart_obj_t *self) {
         __HAL_RCC_UART10_RELEASE_RESET();
         __HAL_RCC_UART10_CLK_DISABLE();
     #endif
+    #if defined(LPUART1)
+    } else if (self->uart_id == PYB_LPUART_1) {
+        HAL_NVIC_DisableIRQ(LPUART1_IRQn);
+        __HAL_RCC_LPUART1_FORCE_RESET();
+        __HAL_RCC_LPUART1_RELEASE_RESET();
+        __HAL_RCC_LPUART1_CLK_DISABLE();
+    #endif
     }
 }
 
@@ -677,7 +712,15 @@ uint32_t uart_get_source_freq(pyb_uart_obj_t *self) {
 
 uint32_t uart_get_baudrate(pyb_uart_obj_t *self) {
     // This formula assumes UART_OVERSAMPLING_16
-    return uart_get_source_freq(self) / self->uartx->BRR;
+    uint32_t source_freq = uart_get_source_freq(self);
+    #if defined(LPUART1)
+    if (self->uart_id == PYB_LPUART_1) {
+        return source_freq / (self->uartx->BRR >> 8);
+    } else
+    #endif
+    {
+        return source_freq / self->uartx->BRR;
+    }
 }
 
 void uart_set_baudrate(pyb_uart_obj_t *self, uint32_t baudrate) {

ports/stm32/uart.h

@@ -40,6 +40,9 @@ typedef enum {
     PYB_UART_8 = 8,
     PYB_UART_9 = 9,
     PYB_UART_10 = 10,
+    #ifdef LPUART1
+    PYB_LPUART_1 = MICROPY_HW_MAX_UART + 1,
+    #endif
 } pyb_uart_t;
 
 #define CHAR_WIDTH_8BIT (0)