CANADC

The CANADC is a simple Data Acquisition System (DAQ) with a Controller Area Network (CAN) interface and a RS-232 interface. It is designed to be a simple and low cost way of reading analog values and putting them on to a vehicle CAN network.

1. Usage Details
2. Technical Details

---

Usage Details

DB-25 Pinout - Inputs

Pin(s)	Description
1	ADC Channel 0
2	ADC Channel 1
3	ADC Channel 2
4	ADC Channel 3
5	ADC Channel 4
6	ADC Channel 5
7	ADC Channel 6
8	ADC Channel 7
9	5 volts
10	5 volts
11	5 volts
12	5 volts
13	5 volts
14	Ground
15	Ground
16	Ground
17	Ground
18	Ground
19	Ground
20	Ground
21	Ground
22	Ground
23	Ground
24	Ground
25	Ground

---

Technical Details

Bill Of Materials

Designator(s)	Description	Part Number
U1	CAN transceiver	MCP2551-I/P
U2	PIC microcontroller	PIC18F2480-I/P
U3	Voltage regulator, 5 volt	LM7805
U4	RS-232 transceiver	MAX202CPE
P1	Power connector, 2.1x5.5mm	CP-201AH
P2	RS-232 connector, DB9 female right angle
P3	CAN connector, DB9 male right angle
P4	In Circuit Serial Programming, 0.1" KK 5 position up
P5	Analog input connector, DB25 female right angle
D1	LED, T1 size
R1	Resistor, 330 ohm
R2	Potentiometer, 10k	Bourns 3386P
R3	Resistor, 10k
R10-R18	Resistor, 2k (analog pull up or pull down)
C1	Capacitor, 100uF electrolytic
C2-C10	Capacitor, 0.1uF monolithic
Y1	Ceramic resonator, 4 MHz

Parts without part number are non-critical.

Printed Circuit Board

The CANADC circuit boards were laid out and manufactured using Pad2Pad. You'll need to install the Pad2Pad client to view or order CANADC boards.

1. canadc.pcb 52k

Here is screen capture of the board file loaded in Pad2Pad:

Source Code and HEX Image

I wrote the software in C and used the PCH compiler from Custom Computer Services.

1. canadc.c Main source code
2. canadc.hex Compiled hex file

You will also need can-18xxx8.c and can-18xxx8.h which are included with the PCH compiler from CCS. By license I'm not allowed to distribute those files, otherwise I would.

You will also need to modify the can_set_baud() function to account for your processor speed and CAN bus parameters. I used "Microchip CAN Bit Timing Calculator" from Interpid Control Systems, Inc. to calculate the BRGCONx values. Then I just hardcoded them in to the can_set_baud() routine.

void can_set_baud(void) {
	/* 16 MHz, 250 kHz CAN bus */
	BRGCON1=0x01;
	BRGCON2=0xb8;
	BRGCON3=0x05;
}