Spectrometer

Alpha Spectrometer

Alpha spectrometer developed during my internship at the IEAP.

Pu-239 Am-241 Cm-244 spectrum (on bare die BPW34 in vacuum)

Protocol

General structure

|----------|---------
|   type   | content...
|----------|---------

If the device receives a packet with invalid type, it responds with an ERROR packet with EUNKNOWN error type.

Host->Device

NOP

This does not do anything, it is recommended to send a bunch of NOPs on opening the serial port to flush any data which might have been left in the device input buffer.

|----------|
|   0x01   |
|----------|

PING

Used by host to check whether the device is alive. Device should respond with PONG.

|----------|
|   0x02   |
|----------|

GET

Used by host to get basic properties. Device should respond with GETRESP.

|----------|---------|
|   0x03   | propid  |
|----------|---------|

SET

Used by host to set basic properties. Propval length depends on the property being set. Note that multi byte values should be sent in little endian.

|----------|---------|----------
|   0x04   | propid  | propval...
|----------|---------|----------

START

Start sampling and sending events.

|----------|
|   0x05   |
|----------|

END

End sampling and sending events.

|----------|
|   0x06   |
|----------|

Device->Host

The most significant bit of the type field is always set to 1.

PONG

Sent as response to host PING.

|----------|
|   0x82   |
|----------|

EVENT

Send event (little endian).

|----------|----------|----------|
|   0x87   |   low    |   high   |
|----------|----------|----------|

GETRESP

|----------|----------|----------
|   0x83   |  propid  |  value...
|----------|----------|----------

The value length depends on the propid and the byte order is little endian.

WAVE

Sends event waveform. This is currently not yet implemented.

|----------|----------|----------
|   0x88   |  length  |  <length> samples, 2 bytes each, Big endian
|----------|----------|----------

ERROR

|----------|----------|
|   0xff   |  errno   |
|----------|----------|

Sent on errors. errno: = 1 EUNKNOWN -- Sent on unknown packet type received = 2 EINKEY -- Sent on invalid key in GET/SET packet = 3 EINOP -- Sent on invalid operation on an existing key (unsuported read/write)

Properties

PROP_FW (0x01)

length = 2

Firmware version version.

PROP_THRESH (0x02)

length = 2

Event trigger threshold.

PROP_BIAS (0x03)

length = 1

Set to 1 if the internal bias generator should be enabled.

PROP_AMP (0x04)

length = 1

Set to 1 if the internal x6 amplifier should be enabled.

PROP_RTHRESH (0x05)

length = 2

If the value is > 0, the events are further filtered based on whether their falling edge is at least N samples longer than the rising edge.

PROP_SERNO (0x06)

length = 2

Serial number of the device. Set at compile time using make SERNO=X