Define serial communication protocol how to#

In the case of receiving a character, it is important to note that the divisor latch access bit (DLAB) must be set to 0 in order to access the U0RBR register which contains the received data. While(!((LINE_SR)&(1<PINS: The PINSEL0 register controls the functions in the lower half of PORT0.Next, both the R0 FIFO and T0 FIFO must be set to 1 to clear the bytes in the respective buffers.įIFO_CR = EN_FIFOCR + R0_RESET_FIFOCR + T0_RESET_FIFOCR // Enable FIFO and reset Rx/Tx FIFO buffers UART FIFO: FIFO is enabled by enabling the FIFO bit in the U0FCR register.LINE_CR &= ~DLAB_LCR // Clear DLAB after setting DLL,DLM

Now that we have access to the U0DLL (UART0 Divisor Latch LSB) register and U0DLM (UART0 Divisor Latch MSB) register, the clock frequency can be entered into the registers.īoth these registers share 8 bits each of the total 16 bits.ĭivisor_Latch_Val = (Clock_Frequency/(16 * BAUDRATE )) ĭLLSB = Divisor_Latch_Val & 0xFF //Lower 8 bits of the divisorĭLMSB = (Divisor_Latch_Val>8) & 0xFF //Higher 8 bits of the divisor.

In our case, we will be setting it as 0 for 1 stop bit. Value is set as 0 for 1 stop bit and 1 for 2 stop bits.

Bit 2 in the U0LCR register selects the number of stop bits.

The 8-bit character length must also be selected through the U0LCR register by entering values for bits 0 and 1.

UART0baudrate = (Clock Frequency/(16*(256 * (U0DLM + U0DLL))*(1+(DivAddVal/MulAddVal))))īut first, we must gain access to these registers by enabling the DLAB bit in the U0LCR register which is bit 7.

The baud rate calculation is done on the basis of values entered in the DLL and DLM registers.

BAUD RATE: There are a few bits that must be set in the U0LCR or the Line Control Register of UART0.Therefore the clock frequency is SystemFrequency/4. In our program, we will be using the default value which is case 1. The following are the functions of the peripheral for different values for PCLK_UART0. Note: However, the reset value will be 0 for PCUART2 (bit 24) and PCUART3 (bit 25) and therefore, the respective bits must be set before using UART2 and UART3. Therefore, it is already powered on reset and even if this step is skipped, the program will work. The reset value of this bit in the power control register is 1. The bit in the PCONP register that controls the clock source to the UART0 peripheral, is PCUART0 or bit 3 in the PCONP register. A particular peripheral block will be turned on or off by gating on or gating of the clock source to that particular block. POWER: This is a register that is used to switch on or off the different peripherals in the LPC 1768 module to increase the power efficiency.* CR - Control Register, SR - Status Register, DR - Data Ready */ The definitions that are used in the program are as follows:.Pin configuration of UART0 module and connection diagram to RS232 level converter

Define serial communication protocol how to#

In this tutorial, we will be learning how to interface the UART0 peripheral to understand the set up of a basic UART communication on the LPC 1768 micro-controller. It has multi-processor addressing modes and has an IrDA mode to support infrared communication as well.It supports built-in DMA (Direct Memory Access) for transmission and reception which is ideal when data of byte size has to be transmitted and the controller has to be relieved from basic data communication to perform other tasks.Which means that they can store 16-bytes of data in a first in first out fashion without overwriting existing data in the FIFO buffer before it gets filled. They support 16 bytes receive and transmit FIFOs.Like any other UART peripheral, they can handle data sizes of 5 to 8 bits.Few of the striking features of these peripherals are: The LPC 1768 micro-controller consists of 4 UART peripherals.