1. By James Cockrell and Justin Loveless
Tiva C ADC
By James Cockrell and Justin Loveless

2. Overview of Analog-Digital Converter (ADC)
Turns an analog voltage into a digital value
Used for sensor measurement
Can be triggered with either SWI’s or HWI’s

3. TM4C ADC Specs Reference voltages: Range & Resolution
VREFP – tied to 3.3V on the Launchpad.
VREFN – tied to ground on the Launchpad.
Range & Resolution
Range = 0  4095
Resolution = 3.3V / 4096 = 8.05 mV (p. 803)
Max Sampling Speed = 1 million samples/second
Hardware Averaging
Averages 4 samples in hardware during conversion
Differential Sampling
Sample the difference between two inputs
Internal Temp Sensor
Can be sampled for chip temp

4. ADC0 and ADC1 There are two 12 bit ADC’s
All input channels and triggers are shared by both ADC’s

5. Sequencers Pick sequencers based on how many samples you want
For our example we only need one sample
Sequencer
Number of Samples
Depth of FIFO
SS3 1
SS2 4
SS1
SS0 8

6. Analog input pins (p.795)
These pins can be used as analog inputs if their alternate functions are enabled
Pin Name
Pin Number
Pin Assignment
AIN0 6
PE3
AIN1 7
PE2
AIN2 8
PE1
AIN3 9
PE0
AIN4 64
PD3
AIN5 63
PD2
AIN6 62
PD1
AIN7 61
PD0
AIN8 60
PE5
AIN9 59
PE4
AIN10 58
PB4
AIN11 57
PB5

7. Triggers (p. 793) Potential triggers include
Controller (software)
Timers
Analog Comparators
PWM
GPIO
Nothing (continuous samples)
Our example will use a software as the trigger

8. Example setup
It’s actually that simple!
3.3V
Tiva C
PE3
Pot
GND

9. Example ADC Code Set up clock for 40 MHz
Enable peripheral ADC0, then reset it to apply changes
Disable ADC0 sequencer 3
Configure ADC sequencer
Configure steps for sequences
Enable peripheral GPIO port E

10. Example ADC Code Activate PE3’s alternate function (AIN0)
Set up interrupt handler for ADC0 sequencer 3
Enable interrupts for ADC0 sequencer 3
Re-enable ADC0 sequencer 3
Enable global interrupts
Post request for ADC conversion (in a loop)

11. Example ADC Code (ISR handler)
Clear interrupt flag for ADC0 Sequencer 3
Wait until conversion is done
Read data, and process it

12. Libraries to include From the TivaWare peripheral drivers:
File path to TivaWare libraries and examples:
C:\ti\TivaWare_C_Series \examples\peripherals

13. Questions?

14. Resources
Grp1/docs/software/LM4F-LaunchPad-05%20-%20ADC.pdf
Chapter 5
Explains the API functions
Tiva C peripheral library and examples download site
TM4C123G- LaunchPad/TM4C123G_LaunchPad_Workshop_Workbook.pdf
Overview and specifications