1. Code review: GPIO, timer, and ISR
EE107 Fall 2017
Lecture 4
Code review: GPIO, timer, and ISR
Networked Embedded Systems Pengyu Zhang

2. What resources are available?
Schematic and PCB layout
MSP430FR5994 MCU datasheet
MSP430FR59xx Family’s User Guide
TI MSP430 Code examples

3. Schematic and PCB layout
Schematic is a representation of the elements of a system using abstract, graphic symbols
Logical representation of a device
Connections between devices
Questions
Which LED to toggle?
What is the GPIO logic for LED on?

4. Schematic and PCB layout
PCB layout shows the physical connections between devices
Very difficult to read…
Map schematic and PCB layout
Important for debugging hardware
Questions
How to debug if LED1 is off?
How to debug the GPIO controlling LED2?

5. Device datasheet Datasheet for the specific MCU we are using
Power, GPIO map, clock…
Functional Block Diagram (Figure 1-1)
How many IO ports do we have?
64-Pin PM Package (Figure 4-4)
Signal Descriptions (Table 4-2)
Multiple functions of an IO pin

6. Family User Guide Register information GPIO register info (Table 12-3)
Timer register info

7. Clock systems
Family User Guide Figure 3-1
Clock sources
Clock signals

8. Clock systems Family User Guide Figure 3-1 Clock sources Clock signals
LFXT
HFXT
DCO
VLO
others
Clock signals

9. Clock systems Family User Guide Figure 3-1 Clock sources Clock signals
ACLK – driving peripheral
MCLK – driving CPUs
SMCLK – driving peripheral
others

10. Timer Interrupt
How do I know which interrupt vector is associated with timer A0?
Table 6-4 in the device datasheet
Identify the interrupt vector from the *.h file
How many interrupt vectors for timer A0?
Page 638 on the user guide