11 of 11

ELM633

ELM633DSB

Elm Electronics – Circuits for the Hobbyist

< http://www.elmelectronics.com/ >

Example Applications (continued)

This mode is entered into automatically if the

RS232Rx input is found to be at an active level for the

entire startup time period. This is the period of time

that it takes for the ELM633 to stabilize on a power-up

or reset, prior to issuing the first ‘ELM633 v2.0’

message. Since pin 4 is shown connected high, if pin 5

is held low for at least the initial period, the device will

immediately enter the AT MA mode, as if a user had

sent the command. This is convenient if one wants to

monitor all LIN bus data, but does not particularly want

to manually have to initiate the monitoring. This would

be useful

if making a ‘smart’ adapter cable, for

example. Circuit power is from three button cells,

which provide 4.5V to the circuit through a momentary

action pushbutton switch. The 4.5V is at the lower

level of recommended voltages, but is still within

specified limits, so works fine.

These examples have hopefully provided enough

information to get you started with LIN devices. The

LIN standard shows considerable promise for low-cost

circuits that can be used in lower speed networks such

as

for

man-machine

interfaces.

While

they

are

relatively new and not too frequently found at this time,

they are beginning to turn up everywhere…

Figure 4. LIN Logic Probe

3.58MHz

27pF

10K

Ω

4.7K

Ω

1

2

3

4

7

6

5

633

8

27pF

2 (RxD)

5 (SG)

3 (TxD)

RS232

Interface

4.7K

Ω

LIN Data

Signal

Ground

LIN

Interface

10K

Ω

22K

Ω

0.01µF

+4.5V