1	SID Receiver overview

Here are the main characteristics of the SID receiver:

• single-channel receiver, tested from 15kHz to 80kHz
• included antenna preamplifier
• active order 4 bandpass filter (bandwidth of less than 200Hz for stations below 30kHz)
• measurement of the RMS amplitude
• linear output (not dB), offset setting
• 12-bits ADC
• USB interface
• power supply included

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Synoptic

0	Printed Circuit Board

0

Tuning

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Assembly

1	Data Transfer Protocol

Here are some details regarding the data transfer protocol between the MAX187 and the RS-232 interface.

The MAX187 signals are connected to the following RS-232 pins:

• /CS ↔ RTS
• SCLK ↔ DTR
• DSR ↔ DOUT

The RS-232 standard defines the positive voltage levels for logic one and negative voltage level for logic zero.

Protocol is detailed in the following documents:

•  MAX187 Datasheet
•  Maxim application note 827. This note contains a C code example.

The overall sequence is described below:

• Unset RTS (RTS=-5V; /CS='1') to deselect MAX187
• Set DTR (DTR=+5V; SCLK='0')
• Set RTS (RTS=+5V; /CS='0') to select MAX187. This starts the conversion.
• Wait till the conversion is done (DOUT must be '1'; DSR=-5V)
• Clock in 12 bits. MSB are first:
  • Unset DTR (DTR=-5V; SCLK='1')
  • Set DTR (DTR=+5V; SCLK='0')
  • Read a bit (signal DOUT, DSR)
• Add a 13^th falling edge:
  • Unset DTR (DTR=-5V; SCLK='1')
  • Set DTR (DTR=+5V; SCLK='0')
• Unset RTS (RTS=-5V; /CS='1') to deselect MAX187
• Unset DTR (DTR=-5V; SCLK='1')