From 1f3e4315275bfbf455e9d29ba9e6453c420ded1f Mon Sep 17 00:00:00 2001 From: Piotr Esden-Tempski Date: Fri, 11 Mar 2011 19:50:44 -0800 Subject: [PATCH] Usart baud rate setting function now uses the new apb1 and apb2 frequency variables. And calculates the full BRR value. --- examples/stm32/stm32-h103/usart/usart.c | 42 +++++++++++++++++++++++-- lib/stm32/usart.c | 17 ++++++++-- 2 files changed, 53 insertions(+), 6 deletions(-) diff --git a/examples/stm32/stm32-h103/usart/usart.c b/examples/stm32/stm32-h103/usart/usart.c index 487ee84c..9692d612 100644 --- a/examples/stm32/stm32-h103/usart/usart.c +++ b/examples/stm32/stm32-h103/usart/usart.c @@ -26,15 +26,45 @@ void clock_setup(void) rcc_clock_setup_in_hse_8mhz_out_72mhz(); /* Enable GPIOC clock. */ - rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_IOPCEN); + rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_IOPAEN | RCC_APB2ENR_IOPBEN | RCC_APB2ENR_IOPCEN); /* Enable clocks for GPIO port B (for GPIO_USART3_TX) and USART3. */ - rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_IOPBEN); - rcc_peripheral_enable_clock(&RCC_APB1ENR, RCC_APB1ENR_USART3EN); + rcc_peripheral_enable_clock(&RCC_APB2ENR, RCC_APB2ENR_USART1EN); + rcc_peripheral_enable_clock(&RCC_APB1ENR, RCC_APB1ENR_USART2EN | RCC_APB1ENR_USART3EN); } void usart_setup(void) { + /* Setup GPIO pin GPIO_USART1_TX. */ + gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, + GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART1_TX); + + /* Setup UART parameters. */ + usart_set_baudrate(USART1, 38400); + usart_set_databits(USART1, 8); + usart_set_stopbits(USART1, USART_STOPBITS_1); + usart_set_mode(USART1, USART_MODE_TX); + usart_set_parity(USART1, USART_PARITY_NONE); + usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE); + + /* Finally enable the USART. */ + usart_enable(USART1); + + /* Setup GPIO pin GPIO_USART2_TX. */ + gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, + GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART2_TX); + + /* Setup UART parameters. */ + usart_set_baudrate(USART2, 38400); + usart_set_databits(USART2, 8); + usart_set_stopbits(USART2, USART_STOPBITS_1); + usart_set_mode(USART2, USART_MODE_TX); + usart_set_parity(USART2, USART_PARITY_NONE); + usart_set_flow_control(USART2, USART_FLOWCONTROL_NONE); + + /* Finally enable the USART. */ + usart_enable(USART2); + /* Setup GPIO pin GPIO_USART3_TX/GPIO10 on GPIO port B for transmit. */ gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO_USART3_TX); @@ -69,9 +99,15 @@ int main(void) /* Blink the LED (PC12) on the board with every transmitted byte. */ while (1) { gpio_toggle(GPIOC, GPIO12); /* LED on/off */ + usart_send_blocking(USART1, c + '0'); /* USART1: Send byte. */ + usart_send_blocking(USART2, c + '0'); /* USART2: Send byte. */ usart_send_blocking(USART3, c + '0'); /* USART3: Send byte. */ c = (c == 9) ? 0 : c + 1; /* Increment c. */ if ((j++ % 80) == 0) { /* Newline after line full. */ + usart_send_blocking(USART1, '\r'); + usart_send_blocking(USART1, '\n'); + usart_send_blocking(USART2, '\r'); + usart_send_blocking(USART2, '\n'); usart_send_blocking(USART3, '\r'); usart_send_blocking(USART3, '\n'); } diff --git a/lib/stm32/usart.c b/lib/stm32/usart.c index f6447765..ead0ef7a 100644 --- a/lib/stm32/usart.c +++ b/lib/stm32/usart.c @@ -17,14 +17,25 @@ * along with this program. If not, see . */ +#include + #include void usart_set_baudrate(u32 usart, u32 baud) { - u32 clock = 72000000; /* FIXME: Don't hardcode this clock! */ + u32 clock = rcc_ppre1_frequency; - /* TODO: Document and explain calculation. */ - USART_BRR(usart) = (u16)((clock << 4) / (baud * 16)); + if (usart == USART1) { + clock = rcc_ppre2_frequency; + } + + /* yes it is as simple as that. The reference manual is + * talking about factional calculation but it seems to be only + * marketting bable to sound awesome. It is nothing else but a + * simple divider to generate the correct baudrate. >_< If I + * am wrong feel free to correct me on that. :) (esden) + */ + USART_BRR(usart) = clock/baud; } void usart_set_databits(u32 usart, u32 bits)