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modlwip.c

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  • uart.c 22.72 KiB
    /*
     * This file is part of the MicroPython project, http://micropython.org/
     *
     * The MIT License (MIT)
     *
     * Copyright (c) 2013, 2014 Damien P. George
     *
     * Permission is hereby granted, free of charge, to any person obtaining a copy
     * of this software and associated documentation files (the "Software"), to deal
     * in the Software without restriction, including without limitation the rights
     * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     * copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in
     * all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
     * THE SOFTWARE.
     */
    
    #include <stdio.h>
    #include <string.h>
    #include <stdarg.h>
    
    #include "py/runtime.h"
    #include "py/stream.h"
    #include "py/mperrno.h"
    #include "py/mphal.h"
    #include "lib/utils/interrupt_char.h"
    #include "lib/utils/mpirq.h"
    #include "uart.h"
    #include "irq.h"
    #include "pendsv.h"
    
    #if defined(STM32F4)
    #define UART_RXNE_IS_SET(uart) ((uart)->SR & USART_SR_RXNE)
    #else
    #define UART_RXNE_IS_SET(uart) ((uart)->ISR & USART_ISR_RXNE)
    #endif
    #define UART_RXNE_IT_EN(uart) do { (uart)->CR1 |= USART_CR1_RXNEIE; } while (0)
    #define UART_RXNE_IT_DIS(uart) do { (uart)->CR1 &= ~USART_CR1_RXNEIE; } while (0)
    
    extern void NORETURN __fatal_error(const char *msg);
    
    void uart_init0(void) {
        #if defined(STM32H7)
        RCC_PeriphCLKInitTypeDef RCC_PeriphClkInit = {0};
        // Configure USART1/6 clock source
        RCC_PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART16;
        RCC_PeriphClkInit.Usart16ClockSelection = RCC_USART16CLKSOURCE_D2PCLK2;
        if (HAL_RCCEx_PeriphCLKConfig(&RCC_PeriphClkInit) != HAL_OK) {
            __fatal_error("HAL_RCCEx_PeriphCLKConfig");
        }
    
        // Configure USART2/3/4/5/7/8 clock source
        RCC_PeriphClkInit.PeriphClockSelection = RCC_PERIPHCLK_USART234578;
        RCC_PeriphClkInit.Usart16ClockSelection = RCC_USART234578CLKSOURCE_D2PCLK1;
        if (HAL_RCCEx_PeriphCLKConfig(&RCC_PeriphClkInit) != HAL_OK) {
            __fatal_error("HAL_RCCEx_PeriphCLKConfig");
        }
        #endif
    }
    
    // unregister all interrupt sources
    void uart_deinit_all(void) {
        for (int i = 0; i < MP_ARRAY_SIZE(MP_STATE_PORT(pyb_uart_obj_all)); i++) {
            pyb_uart_obj_t *uart_obj = MP_STATE_PORT(pyb_uart_obj_all)[i];
            if (uart_obj != NULL && !uart_obj->is_static) {
                uart_deinit(uart_obj);
                MP_STATE_PORT(pyb_uart_obj_all)[i] = NULL;
            }
        }
    }
    
    bool uart_exists(int uart_id) {
        if (uart_id > MP_ARRAY_SIZE(MP_STATE_PORT(pyb_uart_obj_all))) {
            // safeguard against pyb_uart_obj_all array being configured too small
            return false;
        }
        switch (uart_id) {
            #if defined(MICROPY_HW_UART1_TX) && defined(MICROPY_HW_UART1_RX)
            case PYB_UART_1: return true;
            #endif
    
            #if defined(MICROPY_HW_UART2_TX) && defined(MICROPY_HW_UART2_RX)
            case PYB_UART_2: return true;
            #endif
    
            #if defined(MICROPY_HW_UART3_TX) && defined(MICROPY_HW_UART3_RX)
            case PYB_UART_3: return true;
            #endif
    
            #if defined(MICROPY_HW_UART4_TX) && defined(MICROPY_HW_UART4_RX)
            case PYB_UART_4: return true;
            #endif
    
            #if defined(MICROPY_HW_UART5_TX) && defined(MICROPY_HW_UART5_RX)
            case PYB_UART_5: return true;
            #endif
    
            #if defined(MICROPY_HW_UART6_TX) && defined(MICROPY_HW_UART6_RX)
            case PYB_UART_6: return true;
            #endif
    
            #if defined(MICROPY_HW_UART7_TX) && defined(MICROPY_HW_UART7_RX)
            case PYB_UART_7: return true;
            #endif
    
            #if defined(MICROPY_HW_UART8_TX) && defined(MICROPY_HW_UART8_RX)
            case PYB_UART_8: return true;
            #endif
    
            default: return false;
        }
    }
    
    // assumes Init parameters have been set up correctly
    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;
        int uart_unit;
    
        const pin_obj_t *pins[4] = {0};
    
        switch (uart_obj->uart_id) {
            #if defined(MICROPY_HW_UART1_TX) && defined(MICROPY_HW_UART1_RX)
            case PYB_UART_1:
                uart_unit = 1;
                UARTx = USART1;
                irqn = USART1_IRQn;
                pins[0] = MICROPY_HW_UART1_TX;
                pins[1] = MICROPY_HW_UART1_RX;
                __HAL_RCC_USART1_CLK_ENABLE();
                break;
            #endif
    
            #if defined(MICROPY_HW_UART2_TX) && defined(MICROPY_HW_UART2_RX)
            case PYB_UART_2:
                uart_unit = 2;
                UARTx = USART2;
                irqn = USART2_IRQn;
                pins[0] = MICROPY_HW_UART2_TX;
                pins[1] = MICROPY_HW_UART2_RX;
                #if defined(MICROPY_HW_UART2_RTS)
                if (flow & UART_HWCONTROL_RTS) {
                    pins[2] = MICROPY_HW_UART2_RTS;
                }
                #endif
                #if defined(MICROPY_HW_UART2_CTS)
                if (flow & UART_HWCONTROL_CTS) {
                    pins[3] = MICROPY_HW_UART2_CTS;
                }
                #endif
                __HAL_RCC_USART2_CLK_ENABLE();
                break;
            #endif
    
            #if defined(MICROPY_HW_UART3_TX) && defined(MICROPY_HW_UART3_RX)
            case PYB_UART_3:
                uart_unit = 3;
                UARTx = USART3;
                #if defined(STM32F0)
                irqn = USART3_8_IRQn;
                #else
                irqn = USART3_IRQn;
                #endif
                pins[0] = MICROPY_HW_UART3_TX;
                pins[1] = MICROPY_HW_UART3_RX;
                #if defined(MICROPY_HW_UART3_RTS)
                if (flow & UART_HWCONTROL_RTS) {
                    pins[2] = MICROPY_HW_UART3_RTS;
                }
                #endif
                #if defined(MICROPY_HW_UART3_CTS)
                if (flow & UART_HWCONTROL_CTS) {
                    pins[3] = MICROPY_HW_UART3_CTS;
                }
                #endif
                __HAL_RCC_USART3_CLK_ENABLE();
                break;
            #endif
    
            #if defined(MICROPY_HW_UART4_TX) && defined(MICROPY_HW_UART4_RX)
            case PYB_UART_4:
                uart_unit = 4;
                #if defined(STM32F0)
                UARTx = USART4;
                irqn = USART3_8_IRQn;
                __HAL_RCC_USART4_CLK_ENABLE();
                #else
                UARTx = UART4;
                irqn = UART4_IRQn;
                __HAL_RCC_UART4_CLK_ENABLE();
                #endif
                pins[0] = MICROPY_HW_UART4_TX;
                pins[1] = MICROPY_HW_UART4_RX;
                break;
            #endif
    
            #if defined(MICROPY_HW_UART5_TX) && defined(MICROPY_HW_UART5_RX)
            case PYB_UART_5:
                uart_unit = 5;
                #if defined(STM32F0)
                UARTx = USART5;
                irqn = USART3_8_IRQn;
                __HAL_RCC_USART5_CLK_ENABLE();
                #else
                UARTx = UART5;
                irqn = UART5_IRQn;
                __HAL_RCC_UART5_CLK_ENABLE();
                #endif
                pins[0] = MICROPY_HW_UART5_TX;
                pins[1] = MICROPY_HW_UART5_RX;
                break;
            #endif
    
            #if defined(MICROPY_HW_UART6_TX) && defined(MICROPY_HW_UART6_RX)
            case PYB_UART_6:
                uart_unit = 6;
                UARTx = USART6;
                #if defined(STM32F0)
                irqn = USART3_8_IRQn;
                #else
                irqn = USART6_IRQn;
                #endif
                pins[0] = MICROPY_HW_UART6_TX;
                pins[1] = MICROPY_HW_UART6_RX;
                #if defined(MICROPY_HW_UART6_RTS)
                if (flow & UART_HWCONTROL_RTS) {
                    pins[2] = MICROPY_HW_UART6_RTS;
                }
                #endif
                #if defined(MICROPY_HW_UART6_CTS)
                if (flow & UART_HWCONTROL_CTS) {
                    pins[3] = MICROPY_HW_UART6_CTS;
                }
                #endif
                __HAL_RCC_USART6_CLK_ENABLE();
                break;
            #endif
    
            #if defined(MICROPY_HW_UART7_TX) && defined(MICROPY_HW_UART7_RX)
            case PYB_UART_7:
                uart_unit = 7;
                #if defined(STM32F0)
                UARTx = USART7;
                irqn = USART3_8_IRQn;
                __HAL_RCC_USART7_CLK_ENABLE();
                #else
                UARTx = UART7;
                irqn = UART7_IRQn;
                __HAL_RCC_UART7_CLK_ENABLE();
                #endif
                pins[0] = MICROPY_HW_UART7_TX;
                pins[1] = MICROPY_HW_UART7_RX;
                break;
            #endif
    
            #if defined(MICROPY_HW_UART8_TX) && defined(MICROPY_HW_UART8_RX)
            case PYB_UART_8:
                uart_unit = 8;
                #if defined(STM32F0)
                UARTx = USART8;
                irqn = USART3_8_IRQn;
                __HAL_RCC_USART8_CLK_ENABLE();
                #else
                UARTx = UART8;
                irqn = UART8_IRQn;
                __HAL_RCC_UART8_CLK_ENABLE();
                #endif
                pins[0] = MICROPY_HW_UART8_TX;
                pins[1] = MICROPY_HW_UART8_RX;
                break;
            #endif
    
            default:
                // UART does not exist or is not configured for this board
                return false;
        }
    
        uint32_t mode = MP_HAL_PIN_MODE_ALT;
        uint32_t pull = MP_HAL_PIN_PULL_UP;
    
        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);
                if (!ret) {
                    return false;
                }
            }
        }
    
        uart_obj->irqn = irqn;
        uart_obj->uartx = UARTx;
    
        // init UARTx
        UART_HandleTypeDef huart;
        memset(&huart, 0, sizeof(huart));
        huart.Instance = UARTx;
        huart.Init.BaudRate = baudrate;
        huart.Init.WordLength = bits;
        huart.Init.StopBits = stop;
        huart.Init.Parity = parity;
        huart.Init.Mode = UART_MODE_TX_RX;
        huart.Init.HwFlowCtl = flow;
        huart.Init.OverSampling = UART_OVERSAMPLING_16;
        HAL_UART_Init(&huart);
    
        uart_obj->is_enabled = true;
        uart_obj->attached_to_repl = false;
    
        if (bits == UART_WORDLENGTH_9B && parity == UART_PARITY_NONE) {
            uart_obj->char_mask = 0x1ff;
            uart_obj->char_width = CHAR_WIDTH_9BIT;
        } else {
            if (bits == UART_WORDLENGTH_9B || parity == UART_PARITY_NONE) {
                uart_obj->char_mask = 0xff;
            } else {
                uart_obj->char_mask = 0x7f;
            }
            uart_obj->char_width = CHAR_WIDTH_8BIT;
        }
    
        uart_obj->mp_irq_trigger = 0;
        uart_obj->mp_irq_obj = NULL;
    
        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);
            UART_RXNE_IT_DIS(self->uartx);
        } else {
            UART_RXNE_IT_EN(self->uartx);
            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;
    
        // Disable UART
        self->uartx->CR1 &= ~USART_CR1_UE;
    
        // Reset and turn off the UART peripheral
        if (self->uart_id == 1) {
            HAL_NVIC_DisableIRQ(USART1_IRQn);
            __HAL_RCC_USART1_FORCE_RESET();
            __HAL_RCC_USART1_RELEASE_RESET();
            __HAL_RCC_USART1_CLK_DISABLE();
        } else if (self->uart_id == 2) {
            HAL_NVIC_DisableIRQ(USART2_IRQn);
            __HAL_RCC_USART2_FORCE_RESET();
            __HAL_RCC_USART2_RELEASE_RESET();
            __HAL_RCC_USART2_CLK_DISABLE();
        #if defined(USART3)
        } else if (self->uart_id == 3) {
            #if !defined(STM32F0)
            HAL_NVIC_DisableIRQ(USART3_IRQn);
            #endif
            __HAL_RCC_USART3_FORCE_RESET();
            __HAL_RCC_USART3_RELEASE_RESET();
            __HAL_RCC_USART3_CLK_DISABLE();
        #endif
        #if defined(UART4)
        } else if (self->uart_id == 4) {
            HAL_NVIC_DisableIRQ(UART4_IRQn);
            __HAL_RCC_UART4_FORCE_RESET();
            __HAL_RCC_UART4_RELEASE_RESET();
            __HAL_RCC_UART4_CLK_DISABLE();
        #endif
        #if defined(USART4)
        } else if (self->uart_id == 4) {
            __HAL_RCC_USART4_FORCE_RESET();
            __HAL_RCC_USART4_RELEASE_RESET();
            __HAL_RCC_USART4_CLK_DISABLE();
        #endif
        #if defined(UART5)
        } else if (self->uart_id == 5) {
            HAL_NVIC_DisableIRQ(UART5_IRQn);
            __HAL_RCC_UART5_FORCE_RESET();
            __HAL_RCC_UART5_RELEASE_RESET();
            __HAL_RCC_UART5_CLK_DISABLE();
        #endif
        #if defined(USART5)
        } else if (self->uart_id == 5) {
            __HAL_RCC_USART5_FORCE_RESET();
            __HAL_RCC_USART5_RELEASE_RESET();
            __HAL_RCC_USART5_CLK_DISABLE();
        #endif
        #if defined(UART6)
        } else if (self->uart_id == 6) {
            HAL_NVIC_DisableIRQ(USART6_IRQn);
            __HAL_RCC_USART6_FORCE_RESET();
            __HAL_RCC_USART6_RELEASE_RESET();
            __HAL_RCC_USART6_CLK_DISABLE();
        #endif
        #if defined(UART7)
        } else if (self->uart_id == 7) {
            HAL_NVIC_DisableIRQ(UART7_IRQn);
            __HAL_RCC_UART7_FORCE_RESET();
            __HAL_RCC_UART7_RELEASE_RESET();
            __HAL_RCC_UART7_CLK_DISABLE();
        #endif
        #if defined(USART7)
        } else if (self->uart_id == 7) {
            __HAL_RCC_USART7_FORCE_RESET();
            __HAL_RCC_USART7_RELEASE_RESET();
            __HAL_RCC_USART7_CLK_DISABLE();
        #endif
        #if defined(UART8)
        } else if (self->uart_id == 8) {
            HAL_NVIC_DisableIRQ(UART8_IRQn);
            __HAL_RCC_UART8_FORCE_RESET();
            __HAL_RCC_UART8_RELEASE_RESET();
            __HAL_RCC_UART8_CLK_DISABLE();
        #endif
        #if defined(USART8)
        } else if (self->uart_id == 8) {
            __HAL_RCC_USART8_FORCE_RESET();
            __HAL_RCC_USART8_RELEASE_RESET();
            __HAL_RCC_USART8_CLK_DISABLE();
        #endif
        }
    }
    
    void uart_attach_to_repl(pyb_uart_obj_t *self, bool attached) {
        self->attached_to_repl = attached;
    }
    
    uint32_t uart_get_baudrate(pyb_uart_obj_t *self) {
        uint32_t uart_clk = 0;
    
        #if defined(STM32F0)
        uart_clk = HAL_RCC_GetPCLK1Freq();
        #elif defined(STM32F7)
        switch ((RCC->DCKCFGR2 >> ((self->uart_id - 1) * 2)) & 3) {
            case 0:
                if (self->uart_id == 1 || self->uart_id == 6) {
                    uart_clk = HAL_RCC_GetPCLK2Freq();
                } else {
                    uart_clk = HAL_RCC_GetPCLK1Freq();
                }
                break;
            case 1:
                uart_clk = HAL_RCC_GetSysClockFreq();
                break;
            case 2:
                uart_clk = HSI_VALUE;
                break;
            case 3:
                uart_clk = LSE_VALUE;
                break;
        }
        #elif defined(STM32H7)
        uint32_t csel;
        if (self->uart_id == 1 || self->uart_id == 6) {
            csel = RCC->D2CCIP2R >> 3;
        } else {
            csel = RCC->D2CCIP2R;
        }
        switch (csel & 3) {
            case 0:
                if (self->uart_id == 1 || self->uart_id == 6) {
                    uart_clk = HAL_RCC_GetPCLK2Freq();
                } else {
                    uart_clk = HAL_RCC_GetPCLK1Freq();
                }
                break;
            case 3:
                uart_clk = HSI_VALUE;
                break;
            case 4:
                uart_clk = CSI_VALUE;
                break;
            case 5:
                uart_clk = LSE_VALUE;
                break;
            default:
                break;
        }
        #else
        if (self->uart_id == 1
            #if defined(USART6)
            || self->uart_id == 6
            #endif
            ) {
            uart_clk = HAL_RCC_GetPCLK2Freq();
        } else {
            uart_clk = HAL_RCC_GetPCLK1Freq();
        }
        #endif
    
        // This formula assumes UART_OVERSAMPLING_16
        uint32_t baudrate = uart_clk / self->uartx->BRR;
    
        return baudrate;
    }
    
    mp_uint_t uart_rx_any(pyb_uart_obj_t *self) {
        int buffer_bytes = self->read_buf_head - self->read_buf_tail;
        if (buffer_bytes < 0) {
            return buffer_bytes + self->read_buf_len;
        } else if (buffer_bytes > 0) {
            return buffer_bytes;
        } else {
            return UART_RXNE_IS_SET(self->uartx) != 0;
        }
    }
    
    // Waits at most timeout milliseconds for at least 1 char to become ready for
    // reading (from buf or for direct reading).
    // Returns true if something available, false if not.
    bool uart_rx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
        uint32_t start = HAL_GetTick();
        for (;;) {
            if (self->read_buf_tail != self->read_buf_head || UART_RXNE_IS_SET(self->uartx)) {
                return true; // have at least 1 char ready for reading
            }
            if (HAL_GetTick() - start >= timeout) {
                return false; // timeout
            }
            MICROPY_EVENT_POLL_HOOK
        }
    }
    
    // assumes there is a character available
    int uart_rx_char(pyb_uart_obj_t *self) {
        if (self->read_buf_tail != self->read_buf_head) {
            // buffering via IRQ
            int data;
            if (self->char_width == CHAR_WIDTH_9BIT) {
                data = ((uint16_t*)self->read_buf)[self->read_buf_tail];
            } else {
                data = self->read_buf[self->read_buf_tail];
            }
            self->read_buf_tail = (self->read_buf_tail + 1) % self->read_buf_len;
            if (UART_RXNE_IS_SET(self->uartx)) {
                // UART was stalled by flow ctrl: re-enable IRQ now we have room in buffer
                UART_RXNE_IT_EN(self->uartx);
            }
            return data;
        } else {
            // no buffering
            #if defined(STM32F0) || defined(STM32F7) || defined(STM32L4) || defined(STM32H7)
            return self->uartx->RDR & self->char_mask;
            #else
            return self->uartx->DR & self->char_mask;
            #endif
        }
    }
    
    // Waits at most timeout milliseconds for TX register to become empty.
    // Returns true if can write, false if can't.
    bool uart_tx_wait(pyb_uart_obj_t *self, uint32_t timeout) {
        uint32_t start = HAL_GetTick();
        for (;;) {
            if (uart_tx_avail(self)) {
                return true; // tx register is empty
            }
            if (HAL_GetTick() - start >= timeout) {
                return false; // timeout
            }
            MICROPY_EVENT_POLL_HOOK
        }
    }
    
    // Waits at most timeout milliseconds for UART flag to be set.
    // Returns true if flag is/was set, false on timeout.
    STATIC bool uart_wait_flag_set(pyb_uart_obj_t *self, uint32_t flag, uint32_t timeout) {
        // Note: we don't use WFI to idle in this loop because UART tx doesn't generate
        // an interrupt and the flag can be set quickly if the baudrate is large.
        uint32_t start = HAL_GetTick();
        for (;;) {
            #if defined(STM32F4)
            if (self->uartx->SR & flag) {
                return true;
            }
            #else
            if (self->uartx->ISR & flag) {
                return true;
            }
            #endif
            if (timeout == 0 || HAL_GetTick() - start >= timeout) {
                return false; // timeout
            }
        }
    }
    
    // src - a pointer to the data to send (16-bit aligned for 9-bit chars)
    // num_chars - number of characters to send (9-bit chars count for 2 bytes from src)
    // *errcode - returns 0 for success, MP_Exxx on error
    // returns the number of characters sent (valid even if there was an error)
    size_t uart_tx_data(pyb_uart_obj_t *self, const void *src_in, size_t num_chars, int *errcode) {
        if (num_chars == 0) {
            *errcode = 0;
            return 0;
        }
    
        uint32_t timeout;
        if (self->uartx->CR3 & USART_CR3_CTSE) {
            // CTS can hold off transmission for an arbitrarily long time. Apply
            // the overall timeout rather than the character timeout.
            timeout = self->timeout;
        } else {
            // The timeout specified here is for waiting for the TX data register to
            // become empty (ie between chars), as well as for the final char to be
            // completely transferred.  The default value for timeout_char is long
            // enough for 1 char, but we need to double it to wait for the last char
            // to be transferred to the data register, and then to be transmitted.
            timeout = 2 * self->timeout_char;
        }
    
        const uint8_t *src = (const uint8_t*)src_in;
        size_t num_tx = 0;
        USART_TypeDef *uart = self->uartx;
    
        while (num_tx < num_chars) {
            if (!uart_wait_flag_set(self, UART_FLAG_TXE, timeout)) {
                *errcode = MP_ETIMEDOUT;
                return num_tx;
            }
            uint32_t data;
            if (self->char_width == CHAR_WIDTH_9BIT) {
                data = *((uint16_t*)src) & 0x1ff;
                src += 2;
            } else {
                data = *src++;
            }
            #if defined(STM32F4)
            uart->DR = data;
            #else
            uart->TDR = data;
            #endif
            ++num_tx;
        }
    
        // wait for the UART frame to complete
        if (!uart_wait_flag_set(self, UART_FLAG_TC, timeout)) {
            *errcode = MP_ETIMEDOUT;
            return num_tx;
        }
    
        *errcode = 0;
        return num_tx;
    }
    
    void uart_tx_strn(pyb_uart_obj_t *uart_obj, const char *str, uint len) {
        int errcode;
        uart_tx_data(uart_obj, str, len, &errcode);
    }
    
    // this IRQ handler is set up to handle RXNE interrupts only
    void uart_irq_handler(mp_uint_t uart_id) {
        // get the uart object
        pyb_uart_obj_t *self = MP_STATE_PORT(pyb_uart_obj_all)[uart_id - 1];
    
        if (self == NULL) {
            // UART object has not been set, so we can't do anything, not
            // even disable the IRQ.  This should never happen.
            return;
        }
    
        if (UART_RXNE_IS_SET(self->uartx)) {
            if (self->read_buf_len != 0) {
                uint16_t next_head = (self->read_buf_head + 1) % self->read_buf_len;
                if (next_head != self->read_buf_tail) {
                    // only read data if room in buf
                    #if defined(STM32F0) || defined(STM32F7) || defined(STM32L4) || defined(STM32H7)
                    int data = self->uartx->RDR; // clears UART_FLAG_RXNE
                    #else
                    int data = self->uartx->DR; // clears UART_FLAG_RXNE
                    #endif
                    data &= self->char_mask;
                    // Handle interrupt coming in on a UART REPL
                    if (self->attached_to_repl && data == mp_interrupt_char) {
                        pendsv_kbd_intr();
                        return;
                    }
                    if (self->char_width == CHAR_WIDTH_9BIT) {
                        ((uint16_t*)self->read_buf)[self->read_buf_head] = data;
                    } else {
                        self->read_buf[self->read_buf_head] = data;
                    }
                    self->read_buf_head = next_head;
                } else { // No room: leave char in buf, disable interrupt
                    UART_RXNE_IT_DIS(self->uartx);
                }
            }
        }
    
        // Set user IRQ flags
        self->mp_irq_flags = 0;
        #if defined(STM32F4)
        if (self->uartx->SR & USART_SR_IDLE) {
            (void)self->uartx->SR;
            (void)self->uartx->DR;
            self->mp_irq_flags |= UART_FLAG_IDLE;
        }
        #else
        if (self->uartx->ISR & USART_ISR_IDLE) {
            self->uartx->ICR = USART_ICR_IDLECF;
            self->mp_irq_flags |= UART_FLAG_IDLE;
        }
        #endif
    
        // Check the flags to see if the user handler should be called
        if (self->mp_irq_trigger & self->mp_irq_flags) {
            mp_irq_handler(self->mp_irq_obj);
        }
    }