Difference between revisions of "Link Instruments MSO-19"
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***Looks like each 16bits of payload are a register write operation | ***Looks like each 16bits of payload are a register write operation | ||
***register writes are 4bits for addr, 8 bits for value, 2 unused bits and 2 bits im not sure what they are for :) | ***register writes are 4bits for addr, 8 bits for value, 2 unused bits and 2 bits im not sure what they are for :) | ||
**** The simplest explanation for the unused bits is that the device bus width is 7 bits (being a CPLD that is very acceptable). | |||
**** The 2 special bits seem to be synchronization bits. 0x7e violates the conversion (high byte), and that may be used to reset the CPLD parser at the end of the packet. | |||
***.?12 AAAA .?34 5678 | ***.?12 AAAA .?34 5678 | ||
***Conversion is: ((v & 0x3f) | ((v & 0xc0) << 6) | ((a & 0xf) << 8) | (((v ^ 0x20) & 0x20) << 1) | (((v ^ 0x80) & 0x80) << 7)) | ***Conversion is: ((v & 0x3f) | ((v & 0xc0) << 6) | ((a & 0xf) << 8) | (((v ^ 0x20) & 0x20) << 1) | (((v ^ 0x80) & 0x80) << 7)) | ||
Revision as of 00:42, 13 January 2012
The Link Instruments MSO-19 is a 2GSa/s oscilloscope, 200MSa/s logic analyzer, 100MSa/s pattern generator and a TDR. It is also extremely portable and is only $249 (including probe, clips, wires and software).
See Link Instruments MSO-19/Info for more details (such as lsusb -vvv output) about the device.
Hardware
Original software
Link Instruments ships the product with its FrontPanelTM Oscilloscope software. Software is for Windows only. Written in .NET (C#), without any kind of obfuscation, which makes it a real breeze to reverse engineer.
USB protocol
It's just serial-over-USB, supported by the Linux kernel through the cp210x driver, though as of Kernel 2.6.37 it needs to be patched to recognize the Link Instruments Vendor/Product ID (3195:f190).
iSerial was exploited by Link Instruments to store hardware type, hardware revision, calibration quirks and the actual serial number.
- for an iSerial of 4294333650260000000 we have:
- 42943 336 502 6 0 000000
- vbit = 42943 / 10000
- dacoffset = 336
- offsetrange = 502
- hwmodel = 6
- hwrev = 0
- serial number = 000000
- 42943 336 502 6 0 000000
Serial protocol
- Control message
- Fixed header: 0x40, 0x4c, 0x44, 0x53, 0x7e
- Variable size payload, 16bit aligned
- Looks like each 16bits of payload are a register write operation
- register writes are 4bits for addr, 8 bits for value, 2 unused bits and 2 bits im not sure what they are for :)
- The simplest explanation for the unused bits is that the device bus width is 7 bits (being a CPLD that is very acceptable).
- The 2 special bits seem to be synchronization bits. 0x7e violates the conversion (high byte), and that may be used to reset the CPLD parser at the end of the packet.
- .?12 AAAA .?34 5678
- Conversion is: ((v & 0x3f) | ((v & 0xc0) << 6) | ((a & 0xf) << 8) | (((v ^ 0x20) & 0x20) << 1) | (((v ^ 0x80) & 0x80) << 7))
- Byte order is big endian
- Fixed footer: 0x7e
Registers description
There is no way to read from registers, only write is possible.
- Read Sample buffer (1): Write 0 to this register to read the samples buffer.
- Read Trigger status (2): Write 0 to this register to read the trigger status.
- TRIGGER_CONFIG_L (3):
- lsbyte of the threshold value.
- TRIGGER_CONFIG_H (4):
- bits [1:0] hold the msbits of the threshold value
- (1 << 2): Trigger on falling edge
- LA_TRIGGER(5):
- LA_TRIGGER_MASK(6):
- SCOPE_TRIGGER_THRESHOLD(7-8):
- CLKRATE(9-10):
- TRIGGER_WIDTH(11): The trigger width in sample units (mso19 app forces the value to be greater than 3)
- DAC(12-13):
- CONTROL (14):
- (1 << 0): Reset SFM
- (1 << 4): Reset ADC (?)
- (1 << 6): Reset ADC (?)
- (1 << 7): Led on/off
- SLOWMODE(15):