2021年02月03日 | 关于MSP430单片机串口通信数据丢失问题

2021-02-03 来源：eefocus

研究摸索了接近一个星期，把所遇到的问题写出来以供参考。

最开始看一个官方的串口收发数据的示例，然后自己操作后收发数据老是会丢失一个数据，然后看User’s Guide，取消了函数收发的方法直接用寄存器操作，问题解决。

接下来写一个组帧协议，收发完全正常。但是看上去逻辑思维非常的杂乱不清晰，就想整理一下，就开始写函数，进行函数调用。好了，这下问题又来了，数据又会丢失。

接近一个星期研究，发现不是自己写的代码有问题，是官方示例的波特率配置问题。大家都知道波特率表示每秒钟传送的码元符号的个数，是衡量数据传输速率的指标，它用单位时间内载波调制状态改变的次数来表示。晶振为1MHz波特率为115200，我自己改成了9600，问题解决。如何配置波特率在User’s Guide里面有想要的答案，详阅即可。以此单片机MSP430FR2311为例波特率配置在586页：
Setting a Baud Rate
For a given BRCLK clock source, the baud rate used determines the required division factor N:
N = fBRCLK/Baud Rate
The division factor N is often a noninteger value, thus, at least one divider and one modulator stage is
used to meet the factor as closely as possible.
If N is equal or greater than 16, it is recommended to use the oversampling baud-rate generation mode by
setting UCOS16.
NOTE: Baud Rate settings quick set up
To calculate the correct the correct settings for the baud rate generation, perform these
steps:

Calculate N = fBRCLK/Baud Rate [if N > 16 continue with step 3, otherwise with step 2]
OS16 = 0, UCBRx = INT(N) [continue with step 4]
OS16 = 1, UCBRx = INT(N/16), UCBRFx = INT([(N/16) – INT(N/16)] × 16)
UCBRSx can be found by looking up the fractional part of N ( = N - INT(N) ) in table
Table 22-4
If OS16 = 0 was chosen, a detailed error calculation is recommended to be performe

更改后的波特率设置代码如下：
//Configure UART
//SMCLK = 1MHz, Baudrate = 9600
//UCBRx = 6, UCBRFx = 8, UCBRSx = 0x20, UCOS16 = 1
EUSCI_A_UART_initParam param = {0};
param.selectClockSource = EUSCI_A_UART_CLOCKSOURCE_SMCLK;
param.clockPrescalar = 6；//UCBRx = 6
param.firstModReg = 8；//UCBRFx = 8
param.secondModReg = 0x20；//CBRSx = 0x20
param.parity = EUSCI_A_UART_NO_PARITY；
param.msborLsbFirst = EUSCI_A_UART_LSB_FIRST；
param.numberofStopBits = EUSCI_A_UART_ONE_STOP_BIT；
param.uartMode = EUSCI_A_UART_MODE；
param.overSampling = EUSCI_A_UART_OVERSAMPLING_BAUDRATE_GENERATION;//UCOS16 = 1；

MSP430 单片机串口通信数据丢失

上一篇:MSP430F169(五)——时钟

下一篇:MSP430移植FreeRTOS（一） FreeRTOS的代码下载