Braintechnology USB-LPS

Braintechnology USB-LPS

Braintechnology USB-LPS, PCB front

Braintechnology USB-LPS, PCB front details

Braintechnology USB-LPS, PCB back

The Braintechnology USB-LPS is a Cypress FX2 based 16-channel, 24MHz, USB-based logic analyzer and signal/pattern generator.

See Braintechnology USB-LPS/Info for some more details (such as lsusb -vvv output) on the device.

Components

• Cypress CY7C68013A-56PVXC (FX2)
• Atmel ATTiny13-20SU
• LD33 (3.3V voltage regulator)
• 24MHz crystal

Protocol

Firmware upload

The FX2 firmware (3072 bytes in size) is uploaded before every sampling run. Certain bytes in the firmware differ depending on the selected sampling rate.

Starting a sampling run

The host seems to send: 0x00 0x01 0x00 0x00 0x00

Stopping a sampling run

The host seems to send: 0x00 0x00 0x00 0x00 0x00

Sample rates

Sampling with 8 probes: Samplerate Divider Other byte 24 MHz 0x01 0xee 16 MHz 0x02 0xee 15 MHz 0x01 0xae 12 MHz 0x03 0xee 10 MHz 0x02 0xae 8 MHz 0x05 0xee 6 MHz 0x07 0xee 5 MHz 0x05 0xae 4 MHz 0x0b 0xee 3 MHz 0x0f 0xee 2.5 MHz 0x0b 0xae 2 MHz 0x17 0xee 1.5 MHz 0x1f 0xee 1 MHz 0x2f 0xee 800 kHz 0x3b 0xee 750 kHz 0x3f 0xee 600 kHz 0x4f 0xee 500 kHz 0x5f 0xee 400 kHz 0x77 0xee 300 kHz 0x9f 0xee 250 kHz 0xbf 0xee 200 kHz 0xef 0xee 150 kHz 0xc7 0xae 120 kHz 0xf9 0xae

Sampling with 16 probes: Samplerate Divider Other byte       12 MHz 0x03 0xee 10 MHz 0x02 0xae 8 MHz 0x05 0xee 6 MHz 0x07 0xee 5 MHz 0x05 0xae 4 MHz 0x0b 0xee 3 MHz 0x0f 0xee 2.5 MHz 0x0b 0xae 2 MHz 0x17 0xee 1.5 MHz 0x1f 0xee 1 MHz 0x2f 0xee 800 kHz 0x3b 0xee 750 kHz 0x3f 0xee 600 kHz 0x4f 0xee 500 kHz 0x5f 0xee 400 kHz 0x77 0xee 300 kHz 0x9f 0xee 250 kHz 0xbf 0xee 200 kHz 0xef 0xee 150 kHz 0xc7 0xae 120 kHz 0xf9 0xae

The byte values for sampling with 8 or 16 probes are thus identical, the only difference is that the sampling rates 24/16/15MHz are not available when 16 probes are used.

Sample format

• 8 bit sampling: Every sample is a byte, bit 0 is the value of probe 0, bit 7 is the value of probe 7.
• 16 bit sampling: Every sample consists of two bytes.
  • First byte: Bit 0 is the value of probe 0, bit 7 is the value of probe 7.
  • Second byte: Bit 0 is the value of probe 8, bit 7 is the value of probe 15.

Buffer size

Not relevant to the protocol, happens purely in software, on the PC side (by sending the "stop acquisition" command at the correct point in time).

The original software allows setting a buffer size to 1-2433 MB, in 1MB steps. This is simply the amount of data streamed from the device to the PC (there is no device-internal buffer/memory).

Pre-Trigger value

Not relevant to the protocol, happens purely in software, on the PC side.

The original software has a pretrigger setting (a scrollbar); it's unclear whether this is an absolute value or a percentage or something else.

Trigger settings

Not relevant to the protocol, happens purely in software, on the PC side.

The original software allows setting per-probe triggers (4 levels deep). At each level the trigger for that probe can be low, high, or dont-care.