diff options
| -rw-r--r-- | usb/setup/README | 83 | ||||
| -rw-r--r-- | usb/setup/usb_reset_and_setup_lowspeed.pcap | bin | 0 -> 1515 bytes | |||
| -rw-r--r-- | usb/setup/usb_reset_and_setup_lowspeed.sr | bin | 0 -> 28191 bytes |
3 files changed, 83 insertions, 0 deletions
diff --git a/usb/setup/README b/usb/setup/README new file mode 100644 index 0000000..321968d --- /dev/null +++ b/usb/setup/README @@ -0,0 +1,83 @@ +------------------------------------------------------------------------------- +USB device setup (low-speed signalling) +------------------------------------------------------------------------------- + +This is an example capture of USB a plugin and setup sequence. + +Plugin and reset signaling (trace walktrough) +--------------------------------------------- + +The logic analyzer is connected to the D+ and D- signals of the device. As the +device ground is not connected to the LA ground, the signal level at the start +of the trace is arbitrary. + +When the cable is plugged in, DM and DP are pulled down by the host side 15k +pull-down resistors. Next, the power supply level of the device rises and +the 1.5k pull-up resistor signals the connection of a low speed device. + +The host waits for 100ms, according to the attach debounce interval [USB 2.0 +spec, Table 7-14, T_ATTDB] for the connection and device power to become +stable. At 240ms the host signals a reset (SE) condition for 50ms [USB 2.0 +spec, 7.1.7.5, T_DRSTR]. + +After the reset, the host issues keep-alives every 1ms (SE0 for 2 bit times), +to allow the device to recover. 10ms are required, but the Linux kernel waits +at least 100ms. + +At this time, the host knows the port is enabled and the device is in the +DEFAULT state, e.g. it responds to control requests at address 0. It is now +possible to request the Device Descriptor. + +At 398ms, the GET_DEVICE_DESCRIPTOR request is the first condition decoded by +the usb_signalling and stacked protocol decoders. After this request, the +max packet size for the control endpoint is known. + +After the request, some buggy devices may be in a bad state (1), thus there +is a second reset/device recovery cycle. + +There follows a sequence of SET_ADDRESS(13) and more GET_DESCRIPTOR requests. +After the setup, the polling of the INTERRUPT endpoint (EP1) starts. + +--- +(1) The stack requests 64 bytes of device descriptor because otherwise some +devices may return more than requested. Other devices can not cope with this +request, and thus a reset is needed. If all devices where compliant, a request +of just 8 bytes should return the wanted bMaxPacketSize of the device. + + +Decoding in PulseView +--------------------- + +Add a usb_signalling decoder. Set the signalling to "low-speed", next assign +DP to "D+" and DM to "D-". The usb_packet and usb_request PDs can be stacked +on top. + +Creating a PCAP (Wireshark) capture +----------------------------------- + +1. Convert the trace with sigrok-cli. + + $ sigrok-cli -i usb_reset_and_setup_lowspeed.sr \ + -P usb_signalling:dp=DP:dm=DM:signalling=low-speed,usb_packet,usb_request \ + -B usb_request > usb_reset_and_setup_lowspeed.pcap + +2. View with tshark (wireshark command line tool). + + $ tshark -r usb_reset_and_setup_lowspeed.pcap + 1 0.000000 host -> 0.0 USB 64 GET DESCRIPTOR Request DEVICE + 2 0.002258 0.0 -> host USB 82 GET DESCRIPTOR Response DEVICE + 3 0.154975 host -> 0.0 USB 64 SET ADDRESS Request + 4 0.155441 0.0 -> host USB 64 SET ADDRESS Response + 5 0.165960 host -> 13.0 USB 64 GET DESCRIPTOR Request DEVICE + 6 0.168258 13.0 -> host USB 82 GET DESCRIPTOR Response DEVICE + 7 0.168287 host -> 13.0 USB 64 GET DESCRIPTOR Request CONFIGURATION + 8 0.169757 13.0 -> host USB 73 GET DESCRIPTOR Response CONFIGURATION + 9 0.169781 host -> 13.0 USB 64 GET DESCRIPTOR Request CONFIGURATION + 10 0.173834 13.0 -> host USB 98 GET DESCRIPTOR Response CONFIGURATION + 11 0.174505 host -> 13.0 USB 64 SET CONFIGURATION Request + 12 0.175061 13.0 -> host USB 64 SET CONFIGURATION Response + 13 0.175116 host -> 13.0 USBHID 64 SET_IDLE Request + 14 0.175506 13.0 -> host USB 64 URB_CONTROL out + 15 0.175694 host -> 13.0 USB 64 GET DESCRIPTOR Request Unknown type 34 + 16 0.181389 13.0 -> host USB 116 GET DESCRIPTOR Response Unknown type 34 + 17 0.200694 host -> 13.1 USB 64 URB_BULK in diff --git a/usb/setup/usb_reset_and_setup_lowspeed.pcap b/usb/setup/usb_reset_and_setup_lowspeed.pcap Binary files differnew file mode 100644 index 0000000..16089a9 --- /dev/null +++ b/usb/setup/usb_reset_and_setup_lowspeed.pcap diff --git a/usb/setup/usb_reset_and_setup_lowspeed.sr b/usb/setup/usb_reset_and_setup_lowspeed.sr Binary files differnew file mode 100644 index 0000000..a185731 --- /dev/null +++ b/usb/setup/usb_reset_and_setup_lowspeed.sr |