MCP3901EV-MCU16 Microchip Technology, MCP3901EV-MCU16 Datasheet - Page 18

• Manufacturer Part Number: MCP3901EV-MCU16
• Description: BOARD EVAL FOR 2CH ADC MCP3901
• Manufacturer: Microchip Technology

Specifications of MCP3901EV-MCU16

• Number Of Adc's: 2
• Number Of Bits: 24
• Data Interface: SPI™
• Inputs Per Adc: 1 Differential
• Input Range: ±1 V
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: MCP3901
• Silicon Manufacturer: Microchip
• Application Sub Type: ADC
• Kit Application Type: Data Converter
• Silicon Core Number: MCP3901, PIC24F, PIC24H, DsPIC33, PIC18F86J55
• Kit Contents: Board
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

MCP3901 ADC Evaluation Board for 16-Bit MCUs User’s Guide
2.3
DS51845A-page 14
UART COMMUNICATION PROTOCOL
The MCU uses UART to send and receive data to the PC. The TX and RX interrupts
are not used simultaneously in this firmware example, but it is possible to use them, if
the user desires.
As soon as the buffer is filled with data from the ADC, and the SPI interrupt is disabled,
and the TX interrupt is enabled. There are more types of data to be sent from MCU to
the PC. The first to be sent is the data stored in the buffers. Before being sent, each
number is transformed in ASCII characters, that represent the number stored in the
buffer. The start of the transmissions of the buffer data is acknowledged by first
transmitting the character: “!”.
The numbers in the current buffer are delimited by the character “,” and each row ends
with character “0x0D”. After 512 rows, the buffer data transmission is complete. To
signal this, the character “D” is sent out.
Next, the data regarding the MCP3901 configuration and sampling speed is sent out.
After a total of 35 characters sent, the MCP3901 configuration data is fully transmitted.
To signal this, the char “;” is sent to the PC. This character also signals that the result
of a FFT computation will be sent out next.
In the last UART TX interrupt, the TX interrupt is disabled and the RX interrupt is
enabled.
Through the RX interrupt, the MCU will receive the configuration for the MCP3901
desired by the user. The protocol is simple. The first character received must be “D”
from configuration Data. After this character come the values of 6 registers: PHASE,
GAIN, CONFIGH, CONFIGL, STATUS, PPREG8. The first 5 registers can hold values
from 0 to 255 so they are made out of maximum 3 characters. If the equivalent number
is less that 100, the first character will be the space character (“ ”), not zero. The
PREG8 register is a 16-bit register inside the MCU that controls the frequency of the
clock signal from the OC1, therefore controlling the sampling speed of the MCP3901.
Since it is a 16-bit register, the number of characters that create the correct value is 5.
© 2009 Microchip Technology Inc.