Simon Collings - RS-232 Interfacing for Receiver Control

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RS-232 Control of the Yaesu FRG-100

Interface Unit: FIF-232C (converts 5V TTL to RS-232 polar)

Standard Connections Used: TXD, RXD, GND

Flow Control: None (for the equipment featured here)

Type of RS-232 Command Set: Binary, 5-byte fixed length frames (1-byte opcode + 4bytes of data/parameters)

Data Parameters: 4800 bps (fixed), 1 start, 8 data + 2 stop bits

FRG100 Interface

Data must be sent to the radio in 5-byte frames with up to 200 ms between each byte. The format (sent left to right) is as follows:

1	2	3	4	5
4th Arg	3rd Arg	2nd Arg	1st Arg	Opcode

Note: The byte ordering of the frame sequence may be reversed with some models (eg FRG-9600).

Five bytes must always be sent in each RS-232 command enen if there is not four bytes of data - in which case the remaining bytes must be filled with dummy values.

Common Commands

Function

Opcode
(hex)

Arg1

Arg2

Arg3

Arg4

Argument description

Memory Recall

02h

Recalls memory channels 1-50, Lo & Hi,
where ch=01-32h, 33h(Lo) or 34h(Hi)

VFO->M

03h

Copy displayed freq. to memory where
f1 is the memory channel (f1=01-34h)
f2 is the function as below:

f2	function
00h	set
01h	mem clear
02h	recall

Lock

04h

Tuning knob lock, p=0 (unlock), p=1 (lock)

VFO operation

05h

Select VFO operation

M->VFO

06h

Copy memory channel to VFO
(ch=01-34h)

07h

Increment the current frequency,
s=0 (100 kHz), s=1 (1 MHz)

Down

08h

Decrement the current frequency,
s=0 (100 kHz), s=1 (1 MHz)

Set Operating
Frequency

0ah

New operating frequency in BCD format:
Example: To set 14.250MHz the values of
f1-f4 are:

f1	00h
f2	50h
f3	42h
f4	01h

Mode

0ch

Select mode as follows:

m	mode
00h	LSB
01h	USB
02h	CW wide
03h	CW narrow
04h	AM wide
05h	AM narrow
06h	FM
07h	FM

Pacing

0eh

Add n milliseconds (n=0-ffh) delay between
each byte of data returned from the radio

Status Update

10h

Instructs the radio to return status data,
either 1, 18, 19 or 292 bytes
(Note: description not covered here)

Power

20h

Turns the radio on (p=01h) or off (p=00h)

Clock Set

21h

c1	function	c2	c3
00h	12/24hr toggle	c2=00h (24hr) c2=01h (12hr)
01h	Time #1 set	c2=hours (BCD)	c3=min (BCD)
02h	Time #2 set	c2=offset hours (BCD)	c3= offset min (BCD)

Timer/Sleep Time Set

22h

t1	function	t2-t3	t4
01h	On-time set	BCD time hh, mm	00h=on 01h=off
02h	Off-time set	BCD time hh, mm	00h=on 01h=off
03h	Sleep-time set	BCD time hh, mm	00h=on 01h=off

Scan Skip Set

8dh

Select memory channel x (01-31h) to be skipped
y=00h (skip on), y=01h (skip off)

Step Frequency Size

8eh

d=0 increment step size, d=1 decrement size
minimum step size 10Hz (non-FM) or 100Hz (FM)

Read S-meter

f7h

Return meter value (repeated 4 times):

arg4	arg3	arg2	arg1	op
val	val	val	val	f7h

Dim

f8h

LCD backlighting d=00h (On), d=01h (Off)

Read Flags

fah

Instructs radio to return 24 1-bit status flags
(Note: not described further here)

Although the basic principle of operation with each Yaesu model is the same, you can expect to see differences in the command byte ordering and the format of data passed to te radio or returned from it. Since the RS-232 interface is a binary one, it is difficult to debug using text based i/o on your PC (the data values have to be converted to text, in which case the debugging code could also be buggy).