ELM327 commands

With the protocol on elm327, WiCAN answers on its port like an ELM327 adapter. This page lists the AT commands the interpreter knows and how it handles requests, for anyone writing a program against it or reading an app's log. The answers below were captured from a device over TCP.

The conversation

Commands end with a carriage return (\r); case and spaces do not matter. Every answer ends with a carriage return and the prompt >. With linefeeds on (ATL1) a line feed follows each carriage return.

ATZ      ELM327 v1.3a
ATI      OBDLink MX
ATRV     11.6V
ATDP     ISO 15765-4 CAN (11 bit ID, 500 kbaud)
ATDPN    6
ATSP6    OK
0100     7E8064100FFFFFFFF
ATSP3    OK
0100     BUS INIT: ...ERROR
ATXX     ?
STI      ?

AT commands

Command	Answer	What it does
ATZ	ELM327 v1.3a	Reset: every setting back to its default, protocol 6. Anything after ATZ in the same message is ignored.
ATI	OBDLink MX	Identify. Apps that know OBDLink adapters read this.
AT@1	ELM327 v1.3a	The device description.
ATRV	11.6V	The battery voltage, as on the Status tab.
ATD	OK	Settings back to defaults; ATD0 and ATD1 (DLC display) are accepted.
ATE0, ATE1	OK	Echo off or on.
ATL0, ATL1	OK	Linefeeds off or on.
ATS0, ATS1	OK	Spaces between bytes off or on.
ATH0, ATH1	OK	Headers (the CAN id in front of each answer) off or on.
ATM0, ATM1	OK	Memory off or on: accepted, no effect.
ATAT0 to ATAT2	OK	Adaptive timing: accepted, no effect.
ATSPn	OK	Set the protocol. 6 to 9 work; any other number is accepted but every request then fails.
ATDP, ATDPN	the protocol's name, or its number	Describe the protocol.
ATSH xyz	OK	Set the header: the id the next requests go to, 3 digits for 11-bit ids, 6 or 8 for 29-bit ids.
ATCRA xyz	OK	Set the receive address: only answers from that id are passed on. ATCRA alone clears it.
ATCP hh	OK	The priority bits of 29-bit headers.
ATSTh h	OK	The timeout for answers, in units of 4 ms; ATST96 is 600 ms.
ATFCSH, ATFCSD, ATFCSM	OK	The flow control header, data and mode for multi-frame answers.
ATPC	OK	Protocol close: accepted, no effect.
anything else, STI..., VTI...	?	Not supported, including the STN and VT extensions of other adapters.

Protocols

Number	Protocol
6	ISO 15765-4 CAN, 11-bit ids, 500 kbit/s (the default)
7	ISO 15765-4 CAN, 29-bit ids, 500 kbit/s
8	ISO 15765-4 CAN, 11-bit ids, 250 kbit/s
9	ISO 15765-4 CAN, 29-bit ids, 250 kbit/s

The numbers 0 to 5 and A to C are described by ATDP (AUTO, SAE J1850 PWM, ISO 9141-2 and so on) but not served: a request under 1 or 2 answers NO DATA, under the others BUS INIT: ...ERROR. There is no automatic protocol search; apps must set 6 to 9 themselves.

Requests

A request is the hexadecimal bytes to send, 0100 or 221E3B, up to 7 bytes. WiCAN sends them in one CAN frame to the header (0x7DF or 0x18DB33F1 by default, or what ATSH set), waits for answers from 0x7E8 to 0x7EF (0x18DAF100 to 0x18DAF1FF for 29-bit ids, or the id ATCRA set) and prints each answer frame on its own line, with the id in front when headers are on. An odd trailing digit, 01005, is the number of answer frames to expect: WiCAN stops waiting as soon as it has them. Multi-frame answers are handled: WiCAN sends the flow control frame itself and prints the first and consecutive frames as they arrive, 7 bytes each.

Answer	Meaning
7E8 06 41 00 FF FF FF FF (headers and spaces on)	one answer frame: the id, the length, then the data
NO DATA	nothing arrived within the timeout
?	a request of more than 7 bytes, or an unknown command
BUS INIT: ...ERROR	the protocol is not one of 6 to 9