PIC18F27J13-I/SS Microchip Technology, PIC18F27J13-I/SS Datasheet - Page 405

• Manufacturer Part Number: PIC18F27J13-I/SS
• Description: IC PIC MCU 128KB FLASH 28SSOP
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F27J13-I/SS

• Core Size: 8-Bit
• Program Memory Size: 128KB (64K x 16)
• Core Processor: PIC
• Speed: 48MHz
• Connectivity: I²C, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Type: FLASH
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2.15 V ~ 3.6 V
• Data Converters: A/D 10x10b/12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Controller Family/series: PIC18
• Cpu Speed: 48MHz
• Digital Ic Case Style: SSOP
• Supply Voltage Range: 1.8V To 5.5V
• Embedded Interface Type: I2C, SPI, USART
• Rohs Compliant: Yes
• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: I2C, SPI, EUSART
• Maximum Clock Frequency: 48 MHz
• Number Of Programmable I/os: 19
• Number Of Timers: 8
• Operating Supply Voltage: 2 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52715-96, 52716-328, 52717-734, 52712-325, EWPIC18
• Development Tools By Supplier: DM164128, DM180021, DM183026-2, DV164131, MA180030, DM183022, DM183032, DV164136, MA180024
• Minimum Operating Temperature: - 40 C
• On-chip Adc: 12 bit, 10 Channel
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: MA180030 - BOARD DEMO PIC18F47J13 FS USBMA180029 - BOARD DEMO PIC18F47J53 FS USB
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

26.4
There are two separate methods of measuring capaci-
tance with the CTMU. The first is the absolute method,
in which the actual capacitance value is desired. The
second is the relative method, in which the actual
capacitance is not needed, rather an indication of a
change in capacitance is required.
26.4.1
For absolute capacitance measurements, both the
current and capacitance calibration steps found in
Section 26.3 “Calibrating the CTMU Module”
should be followed. Capacitance measurements are
then performed using the following steps:
1.
2.
3.
4.
5.
6.
7.
8.
 2010 Microchip Technology Inc.
Initialize the A/D Converter.
Initialize the CTMU.
Set EDG1STAT.
Wait for a fixed delay, T.
Clear EDG1STAT.
Perform an A/D conversion.
Calculate the total capacitance, C
where I is known from the current source
measurement step (see Section 26.3.1 “Current
Source Calibration”), T is a fixed delay and V is
measured by performing an A/D conversion.
Subtract the stray and A/D capacitance
(C
Calibration”) from C
measured capacitance.
OFFSET
Measuring Capacitance with the
CTMU
ABSOLUTE CAPACITANCE
MEASUREMENT
from Section 26.3.2 “Capacitance
TOTAL
to determine the
TOTAL
= (I * T)/V,
Preliminary
PIC18F47J13 FAMILY
26.4.2
An application may not require precise capacitance
measurements. For example, when detecting a valid
press of a capacitance-based touch sense button,
detecting a relative change of capacitance is of inter-
est. In this type of application, when the touch sense
pad is not being pressed, the total capacitance is the
capacitance of the combination of the board traces, the
A/D Converter, etc. A larger voltage will be measured
by the A/D Converter. When the touch sense pad is
pressed, the total capacitance is larger due to the addi-
tion of the capacitance of the human body, therefore, a
smaller voltage will be measured by the A/D Converter.
Detecting capacitance changes is easily accomplished
with the CTMU using these steps:
1.
2.
3.
4.
5.
The voltage measured by performing the A/D conver-
sion is an indication of the relative capacitance. Note
that in this case, no calibration of the current source or
circuit capacitance measurement is needed. See
Example 26-4 for a sample software routine for a
capacitive touch switch.
Initialize the A/D Converter and the CTMU.
Set EDG1STAT.
Wait for a fixed delay.
Clear EDG1STAT.
Perform an A/D conversion.
CAPACITIVE TOUCH SENSE USING
RELATIVE CHARGE
MEASUREMENT
DS39974A-page 405