ELM ELM327L Manual

Obd to rs232 interpreter

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Description

The ELM327L is a low voltage version of our

popular ELM327 integrated circuit. It supports all of

the features of our current ELM327 IC, and only

differs physically in how pin 6 is used.

The following pages discuss the ELM327L in

detail, how to use it and how to configure it, as well

as providing some background information on the

protocols that are supported. There are also

schematic diagrams and tips to help you to interface

to microprocessors, construct a basic scan tool, and

to use the low power mode. Because of the similarity

with the ELM327, much of this data sheet has been

copied from the ELM327 data sheet.

Throughout this document, we will use the term

'ELM327' to refer to either the ELM327 or the

ELM327L. If there is something different between

the two, we will be specific as to which it applies to.

Applications

• Diagnostic trouble code readers

• Automotive scan tools

• Teaching aids

Block Diagram

LFmode

RS232Rx

RS232Tx

PwrCtrl / Busy

IgnMon / RTS

Filter Cap

ELM327L DSC

4.00 MHz

Memory

XT1

RS232

Command

Interface

Protocol

Interpreter

Power

Control

LDO

status LEDs

Regulator

Elm Electronics – Circuits for the Hobbyist

www.elmelectronics.com

OBD to RS232 Interpreter

Features

• Works with a 2.0V to 5.5V supply

• Universal serial (RS232) interface

• Automatically searches for protocols

• Fully configurable with AT commands

• Low power CMOS design

MCLR

Vmeasure

J1850 Volts

J1850 Bus+

Memory

Filter Cap

LFmode

VPW In

ISO In

PWM In

J1850 Bus-

MCLR

XT2

Converter

and

ISO 15765-4

SAE J1939

ELM327L

Connection Diagram

PDIP and SOIC

(top view)

OBD Tx LED

OBD Rx LED

RS232 Tx LED

RS232 Rx LED

CAN Rx

CAN Tx

ISO L

ISO K

XT1

XT2

RS232 Rx

RS232 Tx

PwrCtrl / Busy

IgnMon / RTS

Vmeasure

A/D

ISO 9141-2

SAE J1850

ISO 14230-4

PWM & VPW

OBD interfaces

1 of 99

Table of Contents

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Summary of Contents for ELM ELM327L

Page 1: The Basics Description
ELM327L OBD to RS232 Interpreter Description Features The ELM327L is a low voltage version of our • Works with a 2.0V to 5.5V supply popular ELM327 integrated circuit. It supports all of • Universal serial (RS232) interface the features of our current ELM327 IC, and only differs physically in how pin 6 is used.
Page 2: Table Of Contents
Setting Timeouts - the AT ST and AT AT Commands....56 SAE J1939 Messages..............57 Using J1939................59 The FMS Standard..............62 The NMEA 2000 Standard............63 Altering Flow Control Messages..........63 Elm Electronics – Circuits for the Hobbyist 2 of 99 ELM327L DSC www.elmelectronics.com...
Page 3 Elm Electronics will not be responsible for any patent infringements arising from the use of these products or information, and does not authorize or warrant the use of any Elm Electronics product in life support devices and/or systems.
Page 4: Pin Descriptions
A momentary (>2µsec) logic low applied to this input ELM327L will be terminated with both a carriage will reset the ELM327L. If unused, this pin should be return and a linefeed character. If it is at a low level, connected to a logic high (V ) level.
Page 5 1 or 5 seconds (as set by RS232Tx (pin 17) PP 0E bit 1) passes, the ELM327L will perform a This is the RS232 data transmit output. The signal ‘Warm Start’ and return to normal operation. A low to...
Page 6: Elm327L Unused Pins
Note that the inputs that are shown with an asterisk (*) may be connected to either a High (V ) or a Low (V level, but the level shown is preferred. Pin 6 is not shown for the ELM327L as it must be connected to a capacitor. Elm Electronics – Circuits for the Hobbyist...
Page 7: Elm327L Absolute Maximum Ratings
3. Be sure to check your CAN transceiver BOR voltage specification as well. Many (e.g. the MCP2551 and MCP2561) go into power on reset if V is reduced below 4.0V. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 7 of 99...
Page 8 Notes (cont’d): 4. The Microchip 18F25K80 documentation states that all of the inputs used by the ELM327L have Schmitt waveshaping on them. Sample testing however, has shown that pin 11 may respond as a standard ‘CMOS’ type input (ie not Schmitt) with a threshold voltage approximately equal to the average of the Schmitt thresholds.
Page 9: Using The Elm327
Messages that are not understood by the ELM327 receiving this string is a good way to confirm that the (syntax errors) will always be signalled by a single computer connections and terminal software settings Elm Electronics – Circuits for the Hobbyist ELM327L DSC 9 of 99 www.elmelectronics.com...
Page 10 NULL characters and remove them if found. Although there are no known issues with the ELM327L’s EUSART, we still recommend that all NULL characters be filtered from data that is received from the ELM327L.
Page 11: At Commands
Warm Start (quick software reset) Other reset all display the device description read the IgnMon input level display the device identifier @3 cccccccccccc store the @2 identifier Elm Electronics – Circuits for the Hobbyist ELM327L DSC 11 of 99 www.elmelectronics.com...
Page 12 CAN Priority to hh (29 bit) TP h Try Protocol h reset the Receive Address filters TP Ah Try Protocol h with Auto search CRA hhh set CAN Receive Address to hhh Elm Electronics – Circuits for the Hobbyist ELM327L DSC 12 of 99 www.elmelectronics.com...
Page 13: At Command Descriptions
('sleep') mode if there is no OBD activity detected for a with CAN Extended Addressing or normal ISO 15765 period of time. That period is adjustable with either bit Elm Electronics – Circuits for the Hobbyist ELM327L DSC 13 of 99...
Page 14 – you may not from a terminal program, you should use PP 0C. see much difference with faster OBD systems). The Since some interface circuits are not able to Elm Electronics – Circuits for the Hobbyist ELM327L DSC 14 of 99 www.elmelectronics.com...
Page 15 PCI bytes are all shown, with a ‘<DATA Some (non-OBD) CAN protocols extend the ERROR’ message beside them). addressing fields by using the first of the eight data Elm Electronics – Circuits for the Hobbyist ELM327L DSC 15 of 99 www.elmelectronics.com...
Page 16 MP command or match’ condition is signalled by setting a mask bit to the DM1 command. In fact, we recommend not using Elm Electronics – Circuits for the Hobbyist ELM327L DSC 16 of 99...
Page 17 (due to a hardware or software problem), the restored at any time with the AT D command. device will go off-line in order to not affect other data Elm Electronics – Circuits for the Hobbyist ELM327L DSC 17 of 99...
Page 18 47K and 10K resistors provide in Figure 9). baud rate. The ELM327L also assumes this same ratio, if V above 4V. If V is 4V or less, the ELM327L assumes a 1:11 ratio as would be achieved with a 47K and 4.7K...
Page 19 Control Messages section (page 63). ‘A’. The number is the same one that is used with the set protocol and test protocol commands. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 19 of 99 www.elmelectronics.com...
Page 20 ECU is in fact still active. This command provides an extra level of filtering One other consideration is that while you may for received messages. A message will be accepted if Elm Electronics – Circuits for the Hobbyist ELM327L DSC 20 of 99 www.elmelectronics.com...
Page 21 You can override this behaviour with these IFR on the input will not turn the power off, but it will commands. interrupt any OBD activity that is in progress. All you Elm Electronics – Circuits for the Hobbyist ELM327L DSC 21 of 99 www.elmelectronics.com...
Page 22 ELM format that reverses the bytes for you. When When the ISO 9141-2 and ISO 14230-4 protocols the J1939 ELM (JE) format is enabled, and you have a are initialized, two special bytes (key words) are J1939 protocol selected, and you provide three data...
Page 23 If pin 5 is connected to a low level, the memory saving the fastest speed, it is best to always send a linefeed will be off by default. character immediately after your carriage returns. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 23 of 99 www.elmelectronics.com...
Page 24 [ Monitor for Receiver hh ] J1939 Protocol, however, it is often desirable to This command is very similar to the AT MA monitor for the multi-byte Parameter Group Numbers Elm Electronics – Circuits for the Hobbyist ELM327L DSC 24 of 99 www.elmelectronics.com...
Page 25 Subsequent OBD requests may show ‘SEARCHING’ >AT MA or ‘BUS INIT’, etc. messages when the protocol is reactivated. Values passed in this way do not affect any that Elm Electronics – Circuits for the Hobbyist ELM327L DSC 25 of 99 www.elmelectronics.com...
Page 26 Once enabled, any value assigned using The default setting is R1, or responses on. the PP hh SV command will be used where the factory Elm Electronics – Circuits for the Hobbyist ELM327L DSC 26 of 99 www.elmelectronics.com...
Page 27 11 bits from that, adds vehicle (unless AT R0 has been chosen). leading zeros, and stores the result in the header storage locations for you. As an example, AT SH 7DF Elm Electronics – Circuits for the Hobbyist ELM327L DSC 27 of 99 www.elmelectronics.com...
Page 28 0 (zero), the ELM327 assumes that you wish to have the length value inserted in that first byte 4 - ISO 14230-4 KWP (5 baud init, 10.4 kbaud) Elm Electronics – Circuits for the Hobbyist ELM327L DSC 28 of 99...
Page 29 Note that CAN Extended Addressing does not use this cause a lot of problems if you do not understand it. value - it uses the one set by the AT TA command. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 29 of 99...
Page 30 (Currently, only protocols 3, 4, and 5 support these messages - nothing is available for CAN. If you require This command is very similar to the AT TP Elm Electronics – Circuits for the Hobbyist ELM327L DSC 30 of 99...
Page 31 This command causes the ELM327 to perform a complete reset as if power were cycled off and then on again. All settings are returned to their default values, Elm Electronics – Circuits for the Hobbyist ELM327L DSC 31 of 99...
Page 32: Reading The Battery Voltage
>AT CV 1247 wish if it improves the readability for you, as they are ignored by the ELM327. Note that you should not provide a decimal point in Elm Electronics – Circuits for the Hobbyist ELM327L DSC 32 of 99 www.elmelectronics.com...
Page 33: Obd Commands
Note that the carriage return character is only a signal to the Elm Electronics – Circuits for the Hobbyist ELM327L DSC 33 of 99...
Page 34: Talking To The Vehicle
Converting it, we get a value of 6904, which seems like a very high value for engine rpm. That’s all that you need to do to prepare the Elm Electronics – Circuits for the Hobbyist ELM327L DSC 34 of 99...
Page 35 If you provide a number for the responses that is too small, the ELM327 will return to the prompt too early, and you may cause bus Elm Electronics – Circuits for the Hobbyist ELM327L DSC 35 of 99...
Page 36: Bus Initiation
ELM329L CAN Interpreter products. depending on the protocol - for ISO 9141, the ELM327 will send 68 6A F1 01 00, and it sends C1 33 F1 3E for Elm Electronics – Circuits for the Hobbyist ELM327L DSC 36 of 99...
Page 37: Interpreting Trouble Codes
1131 received would actually be for the code P1131. The ‘43’ in the above response simply indicates that this is a response to a mode 03 request. The other Elm Electronics – Circuits for the Hobbyist ELM327L DSC 37 of 99...
Page 38: Resetting Trouble Codes
>03 to see the codes (ignore the first byte and read the others in pairs) FIX THE VEHICLE ! >04 to reset the codes Elm Electronics – Circuits for the Hobbyist ELM327L DSC 38 of 99 www.elmelectronics.com...
Page 39: Selecting Protocols
The first versions of the ELM327 used the SAE used in exactly the same way as the AT SP command, recommended search order (protocol 1, 2, 3, etc.), but Elm Electronics – Circuits for the Hobbyist ELM327L DSC 39 of 99...
Page 40 To use your own header (and data) values when attempting to connect to an ECU, do not tell the ELM327 to use protocol 0. Instead, tell it to either use Elm Electronics – Circuits for the Hobbyist ELM327L DSC 40 of 99...
Page 41: Obd Message Formats
Figure 3. An OBD Message ‘header’ bytes data bytes (8 in total) ID bits (11 or 29) 7 data bytes checksum Figure 4. A CAN OBD Message Elm Electronics – Circuits for the Hobbyist ELM327L DSC 41 of 99 www.elmelectronics.com...
Page 42: Setting The Headers
You may find that some requests, being of a low Fluid Temperature. You do not know its address, so priority, may not be answered immediately, possibly Elm Electronics – Circuits for the Hobbyist ELM327L DSC 42 of 99 www.elmelectronics.com...
Page 43 CP command. determining the ones to use with your vehicle. Elm The next byte (‘xx’) describes the type of message Electronics does not maintain lists of this information, that this is, and is set to hex DB for functional and cannot provide any further details for you.
Page 44 >AT SH 7DF The OK shows that the ELM327 has accepted your value. The 11 bit ISO15765-4 CAN standard defines both functional addressing (ID/header = 7DF) and physical Elm Electronics – Circuits for the Hobbyist ELM327L DSC 44 of 99 www.elmelectronics.com...
Page 45: Multiline Responses
CAN systems add this single hex digit (it A final example shows how similar messages goes from 0 to F then repeats), to aid in reassembling Elm Electronics – Circuits for the Hobbyist ELM327L DSC 45 of 99...
Page 46 7E9 10 13 49 04 01 35 36 30 7E9 21 32 38 39 35 34 41 43 7E9 22 00 00 00 00 00 00 00 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 46 of 99 www.elmelectronics.com...
Page 47: Can Message Types
1: 47 50 30 30 52 35 35 ‘<RX ERROR’. 2: 42 31 32 33 34 35 36 In this example, the line that begins with 0: is the Elm Electronics – Circuits for the Hobbyist ELM327L DSC 47 of 99 www.elmelectronics.com...
Page 48: Multiple Pid Requests
There is no feedback as to the specific PID one address when receiving. The section on Filtering being requested. As ECUs get busier, these messages for a Transmitter may be helpful with that. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 48 of 99 www.elmelectronics.com...
Page 49: Can Receive Filtering - The Cra Command
>AT CRA 18 DA F1 XX Elm Electronics – Circuits for the Hobbyist ELM327L DSC 49 of 99 www.elmelectronics.com...
Page 50: Using The Can Mask And Filter
J1939 and either MP or DM1, consider using the FT command instead. Putting this together, the filter needs to be: 111 1110 1000 = 7E8 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 50 of 99 www.elmelectronics.com...
Page 51: Filtering For A Transmitter
SAE J1850, ISO 9141-2 or ISO 14230-4 Messages AT FT hh command looks at this byte 8 bits - often up to 8 data bytes the transmitter 11 or 29 ID bits CAN Messages Elm Electronics – Circuits for the Hobbyist ELM327L DSC 51 of 99 www.elmelectronics.com...
Page 52: Monitoring The Bus
Perhaps you only want to see messages that are being transmitted by the ECU with address 10. To do that, you only need to type: >AT MT 10 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 52 of 99 www.elmelectronics.com...
Page 53: Restoring Order
>AT Z It takes approximately one second for the IC to perform this reset, initialize everything and then test Elm Electronics – Circuits for the Hobbyist ELM327L DSC 53 of 99 www.elmelectronics.com...
Page 54: Using Higher Rs232 Baud Rates
A serial interface has always been provided with connection to a microprocessor. That is certainly an our ELM OBD products, largely due to its versatility. option, and one that allows a full speed connection at Older computers, microprocessors and PDAs can all essentially zero cost.
Page 55 MCLR input. It is not affected by the AT D (set Defaults), or AT WS (Warm Start) commands. * the 75 msec time is adjustable with the AT BRT hh command Elm Electronics – Circuits for the Hobbyist ELM327L DSC 55 of 99 www.elmelectronics.com...
Page 56: Setting Timeouts - The At St And At At Commands
ELM327 called responses digit to that value. ‘Adaptive Timing’. Adaptive Timing actually makes the response time measurements for you, and adjusts the AT ST time to Elm Electronics – Circuits for the Hobbyist ELM327L DSC 56 of 99 www.elmelectronics.com...
Page 57: Sae J1939 Messages
PDU1 Format frame that contains an address, or a document, and manufacturers also have the ability to PDU2 Format frame that does not? The secret lies in Elm Electronics – Circuits for the Hobbyist ELM327L DSC 57 of 99 www.elmelectronics.com...
Page 58 >AT SH xx yy zz The values will be used as follows: xx yy zz 5 bits only Destination Source Priority Format Address Address Figure 5. Setting the J1939 CAN ID Elm Electronics – Circuits for the Hobbyist ELM327L DSC 58 of 99 www.elmelectronics.com...
Page 59: Using J1939
The response means that there like this at a time on the bus, so the response to your are currently no active trouble codes, by the way. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 59 of 99...
Page 60 Notice that the ELM327 separates the priority bits requested. from the PGN information. The ELM327 also uses only If you are familiar with the J1939 standard, you will Elm Electronics – Circuits for the Hobbyist ELM327L DSC 60 of 99 www.elmelectronics.com...
Page 61 >00FECB CAN Priority (AT CP) command. After making the above change, all data requests 7 0EBF9 00 01 04 FF 50 00 04 0B 54 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 61 of 99 www.elmelectronics.com...
Page 62: The Fms Standard
10 seconds, so some patience is required when waiting for the data. The FMS standard is completely open, and still continues to evolve. Originally there were different Elm Electronics – Circuits for the Hobbyist ELM327L DSC 62 of 99 www.elmelectronics.com...
Page 63: The Nmea 2000 Standard
We are occasionally asked about support for the example, to monitor for the Engine Parameters PGN NMEA 2000 marine standard. Elm Electronics does (127488 or hex 1F200), you can not use: not provide specific support for this protocol, but our >AT MP 1F200...
Page 64 These modes are identical to those just described, except that flow control messages are automatically sent after every ISO 15765 message that is received, Elm Electronics – Circuits for the Hobbyist ELM327L DSC 64 of 99 www.elmelectronics.com...
Page 65: Using Can Extended Addresses
ID of 7C0: >AT CRA 7C0 and send with an ID (header) of 7B0: >AT SH 7B0 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 65 of 99 www.elmelectronics.com...
Page 66: Can Input Frequency Matching
250 or 500 kbps setting is not 250 or 500 kbps input is quiet PP 28, b0 is 1 Send Logic While Searching for a Protocol Elm Electronics – Circuits for the Hobbyist ELM327L DSC 66 of 99 www.elmelectronics.com...
Page 67: Programming Serial Numbers
- for example, to save the value 7F, simply send: >AT SD 7F and data is just as easily retrieved using the Read Data command: >AT RD Elm Electronics – Circuits for the Hobbyist ELM327L DSC 67 of 99 www.elmelectronics.com...
Page 68: The Activity Monitor
IC will go to the low power mode after a one described above for the AT LP command. second delay (which allows the controlling circuit a In a similar way, the Activity Monitor may be used Elm Electronics – Circuits for the Hobbyist ELM327L DSC 68 of 99 www.elmelectronics.com...
Page 69 All other bits are for PP 0E. represents an AND gate voltage is low represents an OR gate IgnMon voltage 65 msec (pin 15) monitor debounce Figure 6. Enabling the Low Power Mode Elm Electronics – Circuits for the Hobbyist ELM327L DSC 69 of 99 www.elmelectronics.com...
Page 70 • pin 16 = b6 the voltage is now high IgnMon voltage 1 or 5 sec (pin 15) monitor timer the voltage was low Figure 7. Returning to Normal Operation Elm Electronics – Circuits for the Hobbyist ELM327L DSC 70 of 99 www.elmelectronics.com...
Page 71 - just be sure to protect the ELM327 input circuitry from transients. This usually just requires a series resistor of 1K to 10K in value. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 71 of 99...
Page 72: Programmable Parameters
No matter what software you use, you might get For a version 2.3 ELM327, with only the headers into more serious trouble, should you change the baud Elm Electronics – Circuits for the Hobbyist ELM327L DSC 72 of 99 www.elmelectronics.com...
Page 73: Programmable Parameter Summary
Last Protocol to try during automatic searches 01 to 0C Character echo (AT E default setting) 00 = ON (ON) FF = OFF Linefeed Character 00 to FF Elm Electronics – Circuits for the Hobbyist ELM327L DSC 73 of 99 www.elmelectronics.com...
Page 74 ‘ACT ALERT’ 1 minute before RS232 timeout b2: Ignition control 0: disabled 1: enabled allows low power mode if the IgnMon input goes low Elm Electronics – Circuits for the Hobbyist ELM327L DSC 74 of 99 www.elmelectronics.com...
Page 75 ISO/KWP maximum inter-byte time (P1), and also used for 00 to FF (21 msec) the minimum inter-message time (P2). setting (in msec) = (PP 15 value) x 2.112 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 75 of 99 www.elmelectronics.com...
Page 76 FF = OFF CAN filler byte (always used to provide the extra CAN message 00 to FF bytes when 8 are required, whether formatting is on or not) Elm Electronics – Circuits for the Hobbyist ELM327L DSC 76 of 99 www.elmelectronics.com...
Page 77 (in kbps) = 500 ÷ (PP 2D value) For example, setting this PP to 0A (ie. decimal 10) provides a baud rate of 500/10 = 50 kbps. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 77 of 99...
Page 78 PP 2C b4 to 1, and then PP 2D to 06, the base frequency will be 83.3 kbps. The AT DP command will report 83 kbps, but the actual baud rate will be 83.3x8/7 = 95.2 kbps. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 78 of 99 www.elmelectronics.com...
Page 79: Maximum Can Data Rates
29 bit ID = 210 µsec Sending Data total send time is typically (in µsec): 38.4k 115.2k 500k 11 bit ID 5180 1740 29 bit ID 6475 2175 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 79 of 99 www.elmelectronics.com...
Page 80 The ELM327L RS232 transmit buffer is 2048 bytes in size. Considering that some bytes will be sent while new messages are being stored, this means that at...
Page 81: Microprocessor Interfaces
PP 0E turns these hand-shaking your microprocessor L1-L4 R27-30 470Ω n.c. The ELM327 and your microprocessor should Busy RTS use the same 5V supply 4.00MHz 27pF 27pF Elm Electronics – Circuits for the Hobbyist ELM327L DSC 81 of 99 www.elmelectronics.com...
Page 82: Upgrading Versions
For this reason, you should not example and left pin 16 open, and pin 15 tied to +5V. If replace a clone chip with a genuine ELM chip, unless your circuit did this, there is no problem - you may you are absolutely certain that all 28 pins of the simply replace the old chip with a new one.
Page 83: Example Applications
The ISO data is both sent and received on the strongly recommended that you use a commercial ISO-K line. Pin 12 of the ELM327L reads this data transceiver chip as shown. We show a Microchip through the R20-R21 voltage divider. Because of the...
Page 84 A 10µF capacitor is shown connected to pin 6 of be about 4.2V (rising) and 2.2V (falling). The J1850 the ELM327L. This is required for filtering of the IC’s PWM input is a little different in that it must convert a internal 3.3V supply.
Page 85 22KΩ 4.7KΩ Figure 9. An OBD to USB Interpreter is 5.0V) 10KΩ J1850 Bus + 22KΩ 10KΩ J1850 Bus - 4.7KΩ 47KΩ 4.7KΩ ELM327L pin 14 10KΩ Elm Electronics – Circuits for the Hobbyist ELM327L DSC 85 of 99 www.elmelectronics.com...
Page 86 250 kbps rate (be sure to visit Figure 11. A Low Speed www.maximintegrated.com for more information). 8 (CTS) RS232 Interface (≤ 57.6 kbps) The MAX3222E RS232 transceiver contains Elm Electronics – Circuits for the Hobbyist ELM327L DSC 86 of 99 www.elmelectronics.com...
Page 87 First, while connected to the ELM327 at 38.4 kbps, Elm Electronics – Circuits for the Hobbyist ELM327L DSC 87 of 99 www.elmelectronics.com...
Page 88 Our final example, Figure 15, shows a complete Analog Devices (www.analog.com). In addition to 3.3V circuit using the ELM327L. It is very similar to acting as a level translator, this device also provides Figure 9, but 3.3V parts have been selected for U2, U3...
Page 89 Figure 15. 3KΩ An OBD to USB Interpreter = 3.3V) 22KΩ J1850 Bus + 3.3V 22KΩ 10KΩ J1850 Bus - 4.7KΩ 47KΩ 3KΩ ELM327L pin 14 10KΩ Elm Electronics – Circuits for the Hobbyist ELM327L DSC 89 of 99 www.elmelectronics.com...
Page 90: Modifications For Low Power Standby Operation
Figure 16. Suggestions Without making any wiring changes, you can for devices to consider are the 1N5232B zener diode reduce this current by placing the ELM327L into the or the SA5.0AG TVS. low power standby mode. This only requires sending...
Page 91 24 mA to less than 1 mA (and power from about 300 mW to 8 mW) - a considerable savings. leave further improvements to you. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 91 of 99 www.elmelectronics.com...
Page 92 10KΩ 4.7KΩ 4.7KΩ 22KΩ 4.7KΩ 10KΩ J1850 Bus + Figure 16. 22KΩ 10KΩ Modifications to reduce power J1850 Bus - 4.7KΩ 47KΩ 4.7KΩ ELM327L pin 14 10KΩ Elm Electronics – Circuits for the Hobbyist ELM327L DSC 92 of 99 www.elmelectronics.com...
Page 93: Misc. Information Error Messages And Alerts
BUFFER FULL part of a normal vehicle startup while ‘monitoring all.’ The ELM327L provides an internal 2048 byte storage area (or buffer) that is used to temporarily CAN ERROR store messages before they are sent to the PC. It fills...
Page 94 LV RESET. Note correctly. If you witness one of these, contact Elm that this type of reset is exactly the same as an AT Z Electronics for advice.
Page 95 If you are sure that your vehicle uses an OBDII protocol, then check all of your connections, and the ignition, then try the command again. Elm Electronics – Circuits for the Hobbyist ELM327L DSC 95 of 99 www.elmelectronics.com...
Page 96: Version History
Features: - CAN response pending (7F xx 78) now supports extended addressing AT Commands: C0, C1, FC SM8, FC SM9, FC SMA, FT, FT hh, Programmable Parameters: Elm Electronics – Circuits for the Hobbyist ELM327L DSC 96 of 99 www.elmelectronics.com...
Page 97: Outline Diagrams
Ordering Information ELM327L integrated circuits are 28 pin devices, available in either a 300 mil wide (‘skinny’) Plastic DIP format, or in a 300 mil (7.50 mm body) SOIC surface mount type of package, or in a 208 mil (5.30 mm body) SSOP surface mount package.
Page 98: Index
Low Power Operation, Description, 68-71 Electrical Characteristics, 7-8 Modifications, 90-92 Error Messages, 93-95 LP ALERT, 7, 68-71, 74, 75, 94 ERRxx, 94 LV RESET, 20, 77, 87, 94 Elm Electronics – Circuits for the Hobbyist ELM327L DSC 98 of 99 www.elmelectronics.com...
Page 99 Programming Serial Numbers, 67 Versions, Upgrading, 82 Protocols, list of supported, 28, 39 Voltage, Reading the Battery, 32 Protocols, Selecting, 39-40 Wakeup Messages, 36 Quick Guide for Reading Trouble Codes, 38 Wiring Test, 77, 93, 94 ELM327L DSC 99 of 99...

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