Kecheng KC-330B

Kecheng KC-330B

Status	in progress
Connectivity	USB
Measurement range (A)	30dB - 130dB
Resolution	0.1dB
Accuracy (94dB@1kHz)	1.5dB
Frequency weighting	A, C
Time weighting	F, S

The Kecheng KC-330B is a sound level meter and data logger with USB connectivity.

See Kecheng KC-330B/Info for more details (such as lsusb -vvv output) about the device.

Hardware

• Silicon Labs F320 8-bit MCU with USB interface
• 2 X SG Micro SGM8522 dual rail-to-rail op-amp, SGM8524 quad rail-to-rail op-amp
• Microchip 24LC512 64KB EEPROM
• Texas Instruments CD4053M triple 2-channel multiplexer

Photos

• 

  Back of the device

• 

  PCB, top

• 

  PCB, bottom

• 

  PCB with LCD removed

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  SGM8522/SGM8524

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  Silicon Labs F320

Protocol

The host sends commands to the device via endpoint 2, and receives responses via endpoint 1. A command consists of a single byte, with the MSB (bit 7) cleared, followed by any arguments to the command. The response from the device consists of at least one byte: the command, with the MSB set.

Command	Response	Description
0x01	0x81	Configure device, 6 bytes payload:
		1 Sample interval 0-6, representing 125ms, 500ms, 1s, 2s, 5s, 10s, 60s respectively. 2 Alarm low threshold 3 Alarm high threshold 4 Time weighting: 0=Fast, 1=Slow 5 Frequency weighting: 0=dBA, 1=dBC 6 Data source: 0=memory, 1=real time
0x02	0x82	Identify, response payload is length byte + device model (ASCII)
0x03	0x83	Set date and time, 6 bytes payload:
		1 Last two digits of year, e.g. 0x0d for 2013 2 Month, 1-12 3 Day of month, 1-31 4 Hours 5 Minutes 6 Seconds
0x04		Check device status
	0x84	Device is activated, i.e. logging to memory or live to PC ("log" on the display).
	0xa4	Device is deactivated ("con" or "---" on the display).
0x05	0x85	Get stored measurement info, response has 8 bytes payload:
		1-6 Configuration settings of acquired data, same format as 0x01 command (except 0x11...) 7-8 Big-endian integer representing the number of stored measurements (32000 is the maximum).
0x06	0x86	Get stored start date/time. Response has 6 bytes payload, same format as 0x03 command.
0x07	0x87	Get stored measurements, 3 bytes payload:
		1-2 Big-endian integer representing the sample offset, in blocks of 63 samples. 3 Number of samples to send. This is always the maximum, 0x3f, until the last chunk.
0x08	0x88	Get live measurement, response has 2 bytes payload: big-endian integer representing the dB value X 10