If you have a laptop you probably need a usb to RS-232 interface adapter and a terminal program. Then just connect the RX (receive) input of laptop to the TX (transmit) output of the SL-40. The SL-40 installation manual shows the output message format which will be shown in the terminal program window.
Do you have the Dynon and the SL40 programmed with the correct RS-232 format?
---Insert Copy / Paste from SL40 Installation Manual Appendix E:---
APPENDIX E - SERIAL INTERFACE SPECIFICATIONS
This appendix includes the interface specifications for the RS-232 serial port. The RS-232 port can be used to input active and standby frequencies, and is used to input frequencies from a remote source, such as the SL50 and 2001GPS. The interface format conforms to NMEA
0183 message format specifications.
The format of the RS-232 serial port is as follows:
Baud rate............................................9600
Data bits.............................................8
Stop bits .............................................1
Parity..................................................none
The data format is as follows:
$PMRRC<msg_id><msg_data><chksum><cr>
The checksum is computed by an 8 bit addition of the msg_id and msg_data characters, ignoring carry if any. The resulting 8 bit checksum is converted to two ascii characters by taking the upper and lower nibbles, adding 30h to each, and placing the most significant character first in the data message.
RS-232 OUTPUTS
TRANSCEIVER STATUS
This message is used to output the current transceiver frequencies and status.
Message Format
$PMRRC01mkmkas<chksum><cr>
01 .......message id
mk......active frequency (first mk):
m = frequency in MHz in hexadecimal, where m = frequency - 30h, with
frequency in range of 118 to 136 MHz, or 162 MHz.
k = frequency in kHz where k = (frequency / 25 kHz) + 30h, with frequency in
range of 000 to 975 kHz in 25 kHz steps, or 0 to 39.
mk......standby frequency (second mk):
m = frequency in MHz in hexadecimal, where m = frequency - 30h , with
frequency in range of 118 to 136 MHz, or 162 MHz.
k = frequency in kHz where k = (frequency / 25 kHz) + 30h, with frequency in
range of 000 to 975 kHz in 25 kHz steps, or 0 to 39.
a......... transceiver status:
R = normal receive
M = monitor selected
T = transmit enabled
I = intercom enabled
S = stuck mic
s ......... squelch test setting:
0 = automatic
1 = test selected
Example Message
$PMRRC01G4LFR0F0<cr>
The active frequency is 119.100 MHz, the standby frequency is 124.550 MHz, normal receive function, automatic squelch selected.
This message is output once/second.
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