I am newer for BLE and BT, it confused me with 6 octets BD_ADDR in BT and 4 octets "Access Address" in BLE. what is different or purpose?
I can capture BT HCI on Linux wirewhark
I use wireshark to capture BLE's "Access Address"?
Regards
Robber
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I'm a newbie in the Linux network drivers. I'm trying to enable offload features in an ethernet IP.
This ethernet IP supports TX checksum offloading for only 2 Tx HW queues among the total 8 Tx HW queues. Whether the Linux network stack supports offloading Tx checksum only for a few queues(0 and 1 in this case).
Following is my understanding: The Linux driver declares the offload capabilities in netdev->hw_features, NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM in the case of TXCOE. If the device is enabled for TX checksum offloading, the stack doesn’t perform any checksum calculation or insertion and this is offloaded to the HW for the transmit packets irrespective of the HW queue.
Also what I can see is that tools like ethtool only support Tx/Rx checksum offloading for the whole device. Not on a per queue basis.
So can anyone confirm whether this ethernet IP(with 2 among 8 Tx HW queues alone supporting Tx COE) can handle Tx Checksum offloading properly in Linux with all 8 Tx HW queues enabled?
Refer to question: Get MAC address of bluetooth low energy peripheral
We have board where we have kept MAC id in encrypted form in advertisement packet and reading those MAC-id in our iOS App. Since Apple actually suppress MAC id information for BLE device Will it be problem (App rejection) if manufacturer puts this in packet and app reads it?
I have created an Android app which acts as the central and I have found an implementation of a gatt-server (github.com/Jumperr-labs/python-gatt-server) which is part of bluez.When I am asking with a read request the value of a characteristic from the server, the resulting packets are sent using the HCI ACL protocol which is not right as I know.I have set my adapter to LE only mode using btmgmt but i see the same results.Am I missing something?
Here is the current adapter settings taken from the command 'btmgmt info'
"current settings: powered connectable le advertising secure-conn"
Here is what Wireshark shows
Wireshark
I don't know exactly where you see those ACL packets, but the BLE data packets are indeed sent as ACL data packets over HCI.
If you see that the connection uses Bluetooth Classic, you can from the Android side set the transport parameter to TRANSPORT_LE in the connectGatt call to force BLE.
I have found somewhere that wireshark as well as hcidump does the analyzing on HCI level without being able to see the lower layers.And as soon as in HCI BLE packets are sent as ACL data it's fine!To see the lower layers you must buy a BLE sniffer USB dongle.
I have made an iBeacon scanner using the HM-10, where there may be as many as 20-30 iBeacons within range.
I connect an HM-10 (firmware V540) to my MacBook Air's USB port using the OSEPP FTDI USB-to-serial converter and a USB-mini USB cable.
Using the Arduino or CoolTerm app, I send the following AT commands:
AT+ROLE1
AT+IMME1
AT+RESET
AT+DISI?
This produces a scan of only 6 iBeacons, when I have present in the room about 30 iBeacons (all made using the HM-10 or by Kontakt).
Is this a limit in the scan firmware, or am I missing some other command?
We sent an email to the company about this, in English and Chinese. They responded with the advice to upgrade the firmware to V544. We did this, and now the device found 25 iBeacons on the last scan. You can also vary the scan time from 1-9 seconds.
I have two questions:
Why does Modbus allow only 247 slaves to be connected to the same network?
How it this limitation overcome by Modbus TCP/IP?
1) The address field in the Modbus-defined frame is only 8 bits wide. This would provide for 256 possible slave addresses. Address 0 is reserved as a "broadcast" address.
I can't find a specific reason, but there are presumably eight other "reserved" addresses that are not valid for a slave. 256 - 9 = 247.
2) Modbus TCP/IP is implemented atop standard IPv4 addressing, which is limited only to the size of the local subnet (e.g. 10.10.0.0). Each "gateway" on the network will have its own IP address, so there can be many more than 247 gateways.
In addition, each gateway can have multiple Modbus devices behind it. The number of devices behind such a gateway is limited by the same 8-bit address field, here called the "Unit Identifier".
Reference:
Modbus Protocol Reference Guide
"Modbus" (Wikipedia)