UART Cross Connect Polling

Overview

The purpose of the project is to transfer one byte of data from UART 1 to UART 4 and to transfer a different byte in the opposite direction. Your code must confirm that the received byte matches the transmitted byte.

This project cross connects UARTs 1 and 4 using the wiring diagram shown on slide 10 (the bottom diagram) in Chapter 22 UART. Using 2 jumper cables connect the 4 pins as shown in that diagram. For sample code refer to the three scanned pages (534, 535, and 536) from the textbook in myCourses.

Setup

Use the sample code. Create a new project or warm over an existing project. Be sure to include the startup_stm32l476xx.s file that we have used in every project so far.

Requirements

When testing this I strongly recommend that you become proficient in using the Keil debug. I would set a breakpoint at the beginning of the code I want to test and then single step through it to see that the values are correct.

• Your code must do the following:
1. Initialize the GPIO pins and the two UARTs. Refer to the sample code in the PDFs or the textbook.
2. Send a byte from UART1 by loading 0x5A into the its transmit register.
3. Wait for that transmit operation to complete by checking the corresponding transmit status bit.
4. Now wait for the UART4 receive status register to indicate that a byte was received or for a time-out.
5. For the time-out you can use either a system timer (SysTick) or a counter that causes the code to exit the wait on status bit. Your time-out should be about 0.5 seconds.
6. Test1: Read the received byte and confirm that the value is 0x5A.
7. Test2: Now send the value 0x35 from UART4 to UART1 using the same approach but the opposite UARTs (of course).
8. If Test1 fails light the Red LED.
9. If Test2 fails light the Red LED.
10. If both pass light the Green LED.
11. Be sure to exactly follow the instructions in the uart_crosspolling.c file!
12. Add a feature to use a joystick button to cause you to re-run these two tests and update the LEDs.
13. TIP: The LED and joystick demo has joystick code that you can copy.

References

• STM32 Data Sheet (DS)
• STM32 Reference Manual (RM)
• STM32 Discovery Board Overview
• GPIO guide

Rubric and Late Policy

Rubric is defined in the demo sheet

• UART Crosspolling Review
• Late penalties of 5% per day apply.

Submission

• Submit only uart_crosspolling.c to the UART Cross Connect Polling dropbox
• In class demo of your code is required with a CA or the instructor.
• Do not change any other files!