Contents
What do I need to know about STM32 usart1?
As with all the peripherals on the STM32, the first thing to do is make sure that the peripheral is getting a suitable clock signal and that the pins are properly setup. USART1 is connected to the APB2 peripheral bus and uses pins on GPIOA. Thus, we need to enable the clock for GPIOA.
What kind of pins do you need for USART?
Any USART bidirectional communication requires a minimum of two pins: Receive Data In (RX) and Transmit Data Out (TX). Through these pins, serial data is transmitted and received in normal USART mode. The CK pin is required to interface in synchronous mode. The CTS & RTS pins are required in Hardware flow control mode.
Can a STM32 be used as a serial port?
A serial port if you like. On the STM32 however, it really is universal. This peripheral has a raft of features for a huge range of serial protocols including all the usual asynchronous modes plus IrDA, LIN, Smartcard Emulation and the ability to function as an SPI port… Typical STM32 parts have between 2 and 5 USART peripherals.
How many bits does a USART transmitter send?
The USART transmitter can send data words of either 8 or 9 bits depending on the M bit status. When the transmit enable bit (TE) is set, the data in the transmit shift register is shifted out to the TX pin, and the corresponding clock pulses are output on the CK pin (for synchronous mode).
How to enable idle frame in usartx CR1?
Before data can be sent, the transmitter must first be enabled by setting the USARTx_CR1_TE bit in USARTx_CR1. According to the reference manual, immediately after setting this bit, an idle frame will be sent automatically. I could not observe this when repeatedly clearing and setting the TE bit.
Where is the divisor stored in a USART?
Each USART has a register, USART_BRR, that holds the divisor, stored as a 12.4 unsigned fixed point number. The reference manual is a bit awkward on the matter of what value to store in here but the simple answer is to calculate it from This will get you close enough although you should probably use a rounding factor and do it properly.
When to clear TXE flag in usartx _ Dr?
This bit indicates that data register holds data not yet sent to the TDR shift register. There is no need to directly set or clear the TXE flag, it is cleared when data is written to USARTx_DR and set when that data is transferred to the TDR. An interrupt can be connected to this bit if you want to be sending data under interrupt control.