I am trying to troubleshoot my connection to a cheap elm327 OBDII adapter, can pair it using bluetoothctl and i can trust it, can establish a serial connection using rfcomm, i then proceed to use screen with 9600 baud rate but i struggle to get any data and at the prompt i can only insert two characters ?
I use btmon to capture my bt connection, but i am having trouble understanding it, i see i can connect and exchange MTU rates, from my understanding it use the lowest rate:
= Note: Bluetooth subsystem version 2.22 0.304925
= New Index: 60:F2:62:0B:05:EE (Primary,USB,hci0) [hci0] 0.304925
= Open Index: 60:F2:62:0B:05:EE [hci0] 0.304926
= Index Info: 60:F2:62:0B:05:EE (Intel Corp.) [hci0] 0.304926
@ MGMT Open: bluetoothd (privileged) version 1.22 {0x0001} 0.304927
> HCI Event: Extended Inquiry Result (0x2f) plen 255 #1 [hci0] 1.946471
Num responses: 1
Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
Page scan repetition mode: R1 (0x01)
Page period mode: P0 (0x00)
Class: 0x000000
Major class: Miscellaneous
Minor class: 0x00
Clock offset: 0x4b8e
RSSI: -45 dBm (0xd3)
Name (complete): OBDII
Company: not assigned (29282)
Data: 32327878112233445566aabb0000
@ MGMT Event: Device Found (0x0012) plen 45 {0x0001} [hci0] 1.946526
BR/EDR Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
RSSI: -45 dBm (0xd3)
Flags: 0x00000000
Data length: 31
Name (complete): OBDII
Company: not assigned (29282)
Data: 32327878112233445566aabb0000
Class: 0x000000
Major class: Miscellaneous
Minor class: 0x00
< HCI Command: Inquiry Cancel (0x01|0x0002) plen 0 #2 [hci0] 3.532687
> HCI Event: Command Complete (0x0e) plen 4 #3 [hci0] 3.534686
Inquiry Cancel (0x01|0x0002) ncmd 2
Status: Success (0x00)
@ MGMT Event: Discovering (0x0013) plen 2 {0x0001} [hci0] 3.534740
Address type: 0x01
BR/EDR
Discovery: Disabled (0x00)
< HCI Command: Create Connection (0x01|0x0005) plen 13 #4 [hci0] 3.534748
Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
Packet type: 0xcc18
DM1 may be used
DH1 may be used
DM3 may be used
DH3 may be used
DM5 may be used
DH5 may be used
Page scan repetition mode: R2 (0x02)
Page scan mode: Mandatory (0x00)
Clock offset: 0x0000
Role switch: Allow peripheral (0x01)
> HCI Event: Command Status (0x0f) plen 4 #5 [hci0] 3.535531
Create Connection (0x01|0x0005) ncmd 1
Status: Success (0x00)
> HCI Event: Vendor (0xff) plen 4 #6 [hci0] 6.407132
26 00 01 01 &...
> HCI Event: Connect Complete (0x03) plen 11 #7 [hci0] 6.407938
Status: Success (0x00)
Handle: 256
Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
Link type: ACL (0x01)
Encryption: Disabled (0x00)
< HCI Command: Read Remote Supported Features (0x01|0x001b) plen 2 #8 [hci0] 6.408166
Handle: 256
> HCI Event: Max Slots Change (0x1b) plen 3 #9 [hci0] 6.408950
Handle: 256
Max slots: 5
> HCI Event: Command Status (0x0f) plen 4 #10 [hci0] 6.409923
Read Remote Supported Features (0x01|0x001b) ncmd 1
Status: Success (0x00)
< HCI Command: Write Scan Enable (0x03|0x001a) plen 1 #11 [hci0] 6.410018
Scan enable: No Scans (0x00)
> HCI Event: Command Complete (0x0e) plen 4 #12 [hci0] 6.410968
Write Scan Enable (0x03|0x001a) ncmd 2
Status: Success (0x00)
> HCI Event: Read Remote Supported Features (0x0b) plen 11 #13 [hci0] 6.413957
Status: Success (0x00)
Handle: 256
Features: 0xbf 0xfe 0x8d 0xfa 0xc8 0x2d 0x71 0x83
3 slot packets
5 slot packets
Encryption
Slot offset
Timing accuracy
Role switch
Sniff mode
Power control requests
Channel quality driven data rate (CQDDR)
SCO link
HV2 packets
HV3 packets
u-law log synchronous data
A-law log synchronous data
CVSD synchronous data
Power control
Transparent synchronous data
Broadcast Encryption
Enhanced Data Rate ACL 2 Mbps mode
Enhanced inquiry scan
Interlaced inquiry scan
Interlaced page scan
RSSI with inquiry results
Extended SCO link (EV3 packets)
AFH capable peripheral
LE Supported (Controller)
3-slot Enhanced Data Rate ACL packets
5-slot Enhanced Data Rate ACL packets
Pause encryption
AFH capable central
Enhanced Data Rate eSCO 2 Mbps mode
Extended Inquiry Response
Encapsulated PDU
Erroneous Data Reporting
Non-flushable Packet Boundary Flag
Link Supervision Timeout Changed Event
Inquiry TX Power Level
Extended features
< HCI Command: Read Remote Extended Features (0x01|0x001c) plen 3 #14 [hci0] 6.414046
Handle: 256
Page: 1
> HCI Event: Command Status (0x0f) plen 4 #15 [hci0] 6.414916
Read Remote Extended Features (0x01|0x001c) ncmd 1
Status: Success (0x00)
> HCI Event: Read Remote Extended Features (0x23) plen 13 #16 [hci0] 6.418963
Status: Success (0x00)
Handle: 256
Page: 1/2
Features: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
< HCI Command: Remote Name Request (0x01|0x0019) plen 10 #17 [hci0] 6.419074
Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
Page scan repetition mode: R2 (0x02)
Page scan mode: Mandatory (0x00)
Clock offset: 0x0000
< ACL Data TX: Handle 256 flags 0x00 dlen 10 #18 [hci0] 6.419104
L2CAP: Information Request (0x0a) ident 1 len 2
Type: Extended features supported (0x0002)
> HCI Event: Command Status (0x0f) plen 4 #19 [hci0] 6.419930
Remote Name Request (0x01|0x0019) ncmd 1
Status: Success (0x00)
> HCI Event: Number of Completed Packets (0x13) plen 5 #20 [hci0] 6.425023
Num handles: 1
Handle: 256
Count: 1
> HCI Event: Remote Name Req Complete (0x07) plen 255 #21 [hci0] 6.430003
Status: Success (0x00)
Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
Name: OBDII
@ MGMT Event: Device Connected (0x000b) plen 20 {0x0001} [hci0] 6.430056
BR/EDR Address: 00:10:CC:4F:36:03 (CLP COMPUTER LOGISTIK PLANUNG GmbH)
Flags: 0x00000008
Connection Locally Initiated
Data length: 7
Name (complete): OBDII
> ACL Data RX: Handle 256 flags 0x02 dlen 16 #22 [hci0] 6.437601
L2CAP: Information Response (0x0b) ident 1 len 8
Type: Extended features supported (0x0002)
Result: Success (0x0000)
Features: 0x00000000
< ACL Data TX: Handle 256 flags 0x00 dlen 12 #23 [hci0] 6.437668
L2CAP: Connection Request (0x02) ident 2 len 4
PSM: 3 (0x0003)
Source CID: 64
> HCI Event: Number of Completed Packets (0x13) plen 5 #24 [hci0] 6.441004
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 16 #25 [hci0] 6.453672
L2CAP: Connection Response (0x03) ident 2 len 8
Destination CID: 64
Source CID: 64
Result: Connection successful (0x0000)
Status: No further information available (0x0000)
> ACL Data RX: Handle 256 flags 0x02 dlen 16 #26 [hci0] 6.453675
L2CAP: Configure Request (0x04) ident 1 len 8
Destination CID: 64
Flags: 0x0000
Option: Maximum Transmission Unit (0x01) [mandatory]
MTU: 668
< ACL Data TX: Handle 256 flags 0x00 dlen 16 #27 [hci0] 6.453761
L2CAP: Configure Request (0x04) ident 3 len 8
Destination CID: 64
Flags: 0x0000
Option: Maximum Transmission Unit (0x01) [mandatory]
MTU: 1021
< ACL Data TX: Handle 256 flags 0x00 dlen 18 #28 [hci0] 6.453780
L2CAP: Configure Response (0x05) ident 1 len 10
Source CID: 64
Flags: 0x0000
Result: Success (0x0000)
Option: Maximum Transmission Unit (0x01) [mandatory]
MTU: 668
> HCI Event: Number of Completed Packets (0x13) plen 5 #29 [hci0] 6.459103
Num handles: 1
Handle: 256
Count: 1
> HCI Event: Number of Completed Packets (0x13) plen 5 #30 [hci0] 6.459979
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 18 #31 [hci0] 6.465671
L2CAP: Configure Response (0x05) ident 3 len 10
Source CID: 64
Flags: 0x0000
Result: Success (0x0000)
Option: Maximum Transmission Unit (0x01) [mandatory]
MTU: 1021
< ACL Data TX: Handle 256 flags 0x00 dlen 8 #32 [hci0] 6.465833
Channel: 64 len 4 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Set Async Balance Mode (SABM) (0x2f)
Address: 0x03 cr 1 dlci 0x00
Control: 0x3f poll/final 1
Length: 0
FCS: 0x1c
> HCI Event: Number of Completed Packets (0x13) plen 5 #33 [hci0] 6.474195
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 8 #34 [hci0] 6.481715
Channel: 64 len 4 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Ack (UA) (0x63)
Address: 0x03 cr 1 dlci 0x00
Control: 0x73 poll/final 1
Length: 0
FCS: 0xd7
< ACL Data TX: Handle 256 flags 0x00 dlen 18 #35 [hci0] 6.481922
Channel: 64 len 14 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Info with Header Check (UIH) (0xef)
Address: 0x03 cr 1 dlci 0x00
Control: 0xef poll/final 0
Length: 10
FCS: 0x70
MCC Message type: DLC Parameter Negotiation CMD (0x20)
...skipping...
Source CID: 64
Flags: 0x0000
Result: Success (0x0000)
Option: Maximum Transmission Unit (0x01) [mandatory]
MTU: 668
> HCI Event: Number of Completed Packets (0x13) plen 5 #29 [hci0] 6.459103
Num handles: 1
Handle: 256
Count: 1
> HCI Event: Number of Completed Packets (0x13) plen 5 #30 [hci0] 6.459979
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 18 #31 [hci0] 6.465671
L2CAP: Configure Response (0x05) ident 3 len 10
Source CID: 64
Flags: 0x0000
Result: Success (0x0000)
Option: Maximum Transmission Unit (0x01) [mandatory]
MTU: 1021
< ACL Data TX: Handle 256 flags 0x00 dlen 8 #32 [hci0] 6.465833
Channel: 64 len 4 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Set Async Balance Mode (SABM) (0x2f)
Address: 0x03 cr 1 dlci 0x00
Control: 0x3f poll/final 1
Length: 0
FCS: 0x1c
> HCI Event: Number of Completed Packets (0x13) plen 5 #33 [hci0] 6.474195
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 8 #34 [hci0] 6.481715
Channel: 64 len 4 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Ack (UA) (0x63)
Address: 0x03 cr 1 dlci 0x00
Control: 0x73 poll/final 1
Length: 0
Length: 0
FCS: 0xd7
< ACL Data TX: Handle 256 flags 0x00 dlen 18 #35 [hci0] 6.481922
Channel: 64 len 14 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Info with Header Check (UIH) (0xef)
Address: 0x03 cr 1 dlci 0x00
Control: 0xef poll/final 0
Length: 10
FCS: 0x70
MCC Message type: DLC Parameter Negotiation CMD (0x20)
Length: 8
dlci 4 frame_type 0 credit_flow 15 pri 7
ack_timer 0 frame_size 663 max_retrans 0 credits 7
> HCI Event: Number of Completed Packets (0x13) plen 5 #36 [hci0] 6.484969
Num handles: 1
dlci 4 frame_type 0 credit_flow 15 pri 7
ack_timer 0 frame_size 663 max_retrans 0 credits 7
> HCI Event: Number of Completed Packets (0x13) plen 5 #36 [hci0] 6.484969
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 18 #37 [hci0] 6.493479
Channel: 64 len 14 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Info with Header Check (UIH) (0xef)
Address: 0x01 cr 0 dlci 0x00
Control: 0xef poll/final 0
Length: 10
FCS: 0xaa
MCC Message type: DLC Parameter Negotiation RSP (0x20)
Length: 8
dlci 4 frame_type 0 credit_flow 14 pri 7
ack_timer 0 frame_size 662 max_retrans 0 credits 0
< ACL Data TX: Handle 256 flags 0x00 dlen 8 #38 [hci0] 6.493701
Channel: 64 len 4 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Set Async Balance Mode (SABM) (0x2f)
Address: 0x13 cr 1 dlci 0x04
Control: 0x3f poll/final 1
Length: 0
FCS: 0x96
> HCI Event: Number of Completed Packets (0x13) plen 5 #39 [hci0] 6.498304
Num handles: 1
Handle: 256
Count: 1
> ACL Data RX: Handle 256 flags 0x02 dlen 8 #40 [hci0] 6.498359
Channel: 64 len 4 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Ack (UA) (0x63)
Address: 0x13 cr 1 dlci 0x04
Control: 0x73 poll/final 1
Length: 0
FCS: 0x5d
< ACL Data TX: Handle 256 flags 0x00 dlen 12 #41 [hci0] 6.498649
Channel: 64 len 8 [PSM 3 mode Basic (0x00)] {chan 0}
RFCOMM: Unnumbered Info with Header Check (UIH) (0xef)
Address: 0x03 cr 1 dlci 0x00
Control: 0xef poll/final 0
Length: 4
FCS: 0x70
MCC Message type: Modem Status Command CMD (0x38)
Length: 2
dlci 4
fc 0 rtc 1 rtr 1 ic 0 dv 1
i'm seeing "RFCOMM: Unnumbered Ack (UA) (0x63)" which i am not sure what it means, and it seems from there onwards the connection has some problems, "RFCOMM: Unnumbered Info with Header Check (UIH)" is another one i spoted but not sure what it is.
what am i missing ?
manpage. Useapt-cache search OBD2; apt-cache search OBDIIto find the packages.