DFR CAN Module

This CAN module is capable of transmitting 8 analog readings and up to 16 digital readings. The module will send up to two messages with analog data and up to 1 message with digital data depending on the amount of readings requested.

Data Packaging:

Analog:

• Analog pins read from 0-1023, which requires two bytes to transmit. Because the included CAN library requires data to be formatted as a uint8_t array 8 items long, analog readings are split into two values prior to transmission. The two values must be recombined on the receiving end. The high byte is sent first and the low byte is sent second.

Digital:

• Digital readings are packaged into two uint8_t variables (first two items of the output array). The bits are set with bitwise operators and can be read back that way as well (with & instead of |).

Configuration:

The module can be configured to send anywhere from 0 to 8 analog readings and 0 to 16 digital readings with any valid message IDs via the macros at the top of the program file.

• ANALOG_QUANTITY defines the number of analog readings to be sent. The module will start by reading A0, and will sequentially read the analog pins until the quantity requested is satisfied. If this quantity is set to 0, no messages will be sent with analog data; if this quantity is in the range 1-4, one message will be sent with analog data; if this quantity is in the range 5-8, two messages will be sent with analog data. THIS QUANTITY MUST BE IN THE RANGE 0-8.
• DIGITAL_QUANTITY operates much the same way. It defines the number of digital readings to be sent. The module, as above, will start by reading D0, and will sequentially read the digital pins until the quantity requested is satisfied. If the quantity is 0, no message will be sent with digital data; if this quantity is in the range 1-16, one message will be sent with digital data. THIS QUANTITY MUST BE IN THE RANGE 0-16.
• ANALOG1_ID determines the message ID to be associated with the first message containing analog data. This message contains the first half of the requested readings. This must be given a valid value even if the message will not be sent (if no analog data was requested).
• ANALOG2_ID determines the message ID to be associated with the second message containing analog data. This message contains the second half of the requested readings. This must be given a valid value even if the message will not be sent (if less than 5 analog readings were requested).
• DIGITAL_ID determines the message ID of the message containing digital data. This must be given a valid value even if the message will not be sent (if no digital data was requested).
• TRANSMIT_FREQUENCY determines the delay between sets of messages in milliseconds. If this value is set to zero the module will send messages as fast as it can, potentially congesting the CAN network.
• MESSAGE_DELAY determines the delat between individual messages in a set in milliseconds. If this is set to zero, the messages will be sent back to back (depending on the receiving device, this may result in messages being lost). This does not impact the transmission frequency.
• CAN_BAUD_RATE sets the baud rate of the can port. The standard for automotive applications is 500000 (500kbps).

Example:

#define ANALOG_QUANTITY         5
#define DIGITAL_QUANTITY        7
#define ANALOG1_ID              150
#define ANALOG2_ID              151
#define DIGITAL_ID              178
#define TRANSMIT_FREQUENCY      25
#define MESSAGE_DELAY           5
#define CAN_BAUD_RATE           500000

The above settings will result in 5 analog readings being sent and 7 digital readings. The message IDs 150, 151, and 178 will be used for the two analog messages and single digital message respectively.

The following message output can be expected:
id 150 ide 1 rtr 0 dlc 8 data 00 D0 02 65 01 FF 00 00 <- four analog readings
id 151 ide 1 rtr 0 dlc 8 data 00 0B 00 00 00 00 00 00 <- one analog reading with padding
id 178 ide 1 rtr 0 dlc 8 data D7 F8 00 00 00 00 00 00 <- 7 digital readings padded

These messages can be interpreted as follows:
Message 150
00 D0 02 65 01 FF 00 00 <- pairs of hex values split in half
00D0 0265 01FF 0000 <- full hex values
208 613 511 0 <- analog readings
A0 = 208; A1 = 613; A2 = 511; A3 = 0

Message 151
00 0b 00 00 00 00 00 00 <- pairs of hex values
000b 0000 0000 0000 <- full hex values
11 0 0 0 <- one analog reading padded with zeroes
11 <- analog reading
A4 = 11

Message 178
D7 F8 00 00 00 00 00 00 <- two bytes with digital readings padded by zeroes
D7 F8 <- two bytes with digital readings, represented as hex
11010110 00000000 <- seven digital values padded with zeroes
1101011 <- seven digital values
D0 = 1; D1 = 1; D2 = 0; D3 = 1; D4 = 0; D5 = 1; D6 = 1

Hardware Pinout: