Comunicación Serie - Capitulo 3 -Comunicación vía UART método polling y algo más

Communication via UART in LPC845: Polling Strategies

Overview of UART Configuration

• The chapter discusses configuring the UART for communication with another device, emphasizing that correct parameters are crucial for data transmission.

• It highlights the importance of analyzing UART registers while operating without interrupts, focusing on polling methods instead.

Data Reception Process

• The receiver shift register accumulates bits as they are received; an example is given with 8-bit frames at a baud rate of 19200 and even parity.

• Upon receiving the start bit, the UART transitions from idle to receiving state, utilizing a counter to track incoming bits until eight data bits are collected.

Parity and Stop Bit Verification

• After receiving all data bits, the parity bit is checked against expected values; if matched, a parity OK flag is raised.

• The stop bit's timely arrival confirms successful reception; however, the receiver buffer must be cleared for subsequent data.

Application Layer Interaction

• In polling mode, application code must check the Data Ready flag within the status register to read received data correctly.

• If Data Ready is active, it indicates new data in the reception buffer; reading this clears the flag automatically in many cases.

Error Handling During Reception

• If new data arrives before previous data is read, an overrun error occurs. Application code should handle such errors by checking relevant flags.

• Errors like incorrect parity or missing stop bits activate specific error flags; these need to be monitored for effective communication management.

Memory Map and Register Access

• Registers RXD (received data register) and STAT (status register) are essential for monitoring received characters and their associated error flags.

• Some status bits are read-only while others can be cleared by writing a one to them. Understanding these behaviors is critical for proper operation.

Transmission Process Overview

• The process of transmitting involves using both transmitter holding registers and shift registers. Writing to TXD initiates transmission without waiting for prior transmissions to complete.

• Flags indicate whether writing can occur without overwriting existing data. Proper management ensures smooth operation during continuous transmissions.

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Overview of Transmission Code

Implementation of Polling Transmitter

• The discussion begins with the transmission process, focusing on TX ready flags and how to implement a polling transmitter method that receives data for transmission.

• It is noted that if the TX ready flag is set, the data will be written to txd, and the return value will be modified accordingly.

Signal Verification

• The importance of considering the BC signal is highlighted, suggesting an additional line for its verification in the code implementation.

• Acknowledgment that more code may be required to handle this signal effectively.

Registers and Flags in Communication

Common Registers and Flags

• An overview of classic registers and flags used in transmission and reception processes across various microcontroller families is provided.

• Emphasis on how these registers and flags are essential for communication involving three threads: TX, RX, and others.

LPC 845 State Indicators

• Introduction to additional indicators present in the LPC 845 state register similar to txid, which indicates when data reception is occurring.

• The Start signal's purpose is explained as allowing wake-up from deep sleep mode; it resets by writing a one according to documentation.

Conclusion on Reception Process

RX Break Signal

• Discussion about Delta RX break being similar to a break signal but requiring manual reset by writing a one once conditions change.

Noise Detection

• Explanation of RX noid indicating noise detection during reception; it activates when any sample differs from expected values during bit processing.

Future Topics

• Mention of upcoming content focused on handling this same process through interrupts in future videos.