RS422 to RS232 Converter

This box would be used for connecting to a transponder like the Garmin GTX345, and connecting to a GDL90 RS232 supporting EFIS such as the Chelton EFIS.  The GTX345 has the horrible limitation of not being able to send traffic and weather via GDL90 using RS232, and even under RS422 it only sends using 115,200 baud which isn't supported on all EFIS systems.  Using this box you can convert RS422 to RS232 and also down shift the baud rate and still process traffic to ensure you don't overflow the RS232 capabilities.

The RS422 to RS232 version of this box shares many things with the standard version, but also has many differences.  First, there is no need for the Altitude encoder and Squawk code, because your GTX345 transponder does all of that.  So code wise, it only needs to take in GDL90 in RS422 format, and put out GDL90 at RS232 voltage levels.  Hardware wise, you only need 1 MAX3222 chip to do the RS232 output, and one RS422 chip to handle the input.  The board we have made was an original design where we tried to do all in one, where you could populate it with either 2 RS232 chips, or 1 of each, and leave one socket empty.  So when building the system, you choose to EITHER populate IC3 or IC4, but not both.  IC2 is the one used for RS232.

The Shopping List


Quantity
Approx
Price

Description

Digi-Key p/n

Mouser p/n
1
$31 for 3
Oshpark Circuit Board   Order from OSH Park


1
$8
2.54mm Header Pins 40-pin Female Amazon Link

1
$5
Murata OKI-78SR-5/1.5-W36H-C  5V DC/DC Converter 811-2692-ND
580-OKI78SR51.5W36HC
1
$.47
Kemet A758BG106M1EAAE070 10uF 25V Capacitor  (Used for C9)
A758BG106M1EAAE070-ND
80-A758BG106M1EAAE70
3
$.12
Wurth WCAP-ATG5 50V .10uF capactitors 860020672001
(Note: You can use these *or* non-polarized Ceramic on the RS232 ICs;  use these on the input power filter C10 and C11)
732-8847-1-ND
710-860020672001
4
$.40
Murata RCER71H104K0DBH03A  0.1uF +/-10% 50V Ceramic Capacitors X7R (Automotive Grade)
(These are good to use on the 8 spots required by the MAX3222 IC:   C1 thru C8)
490-7514-1-ND
81-RCER71H104K0DBH3A
1
$6.50
MAX32222EEPN+ RS-232 3-5.5V 250kbps transceiver MAX3222EEPN+-ND
700-MAX3222EEPN
1
$11.66
MAX3097EEPE+ RS-422/RS-485 Interface IC 10Mbps 3v/5v Quad RS-422/RS-485 Rcvr
MAX3097EEPE+-ND
700-MAX3097EEPE
1
$3.60
Harting D-Sub board mount Female 15-pin connector 09682537612 1195-5133-ND
617-09682537612
1
$2.00
Mill-Max 18-pin gold plated IC Socket 110-43-318-41-001000 ED90035-ND
575-11043318
1
$1.26
Mill-Max 16-pin gold Plated IC Socket 110-43-316-41-001000
ED90034-ND
575-110433161
1
$2.00
15-pin D-Sub Backshell 86303638BLF 609-1425-ND
649-86303638BLF
1
$37.00
SparkFun Teensy 3.6 WITH Header Pin Board 1568-1465-ND
474-DEV-14058
1
$13.00
Hammond 3.2x2.2x.91" Extruded Aluminum Enclosure 1455C801 HM969-ND
546-1455C801
1
$.80
Cinch D-Sub Connector 15-pin Male 40-9815M   (To mate to "the box")
367-1190-ND
601-40-9815M
2
$.30
4-40 thread Female Screwlocks 5207953-3 or 5748558-3 or similar  (Or pull them off a junk PC for free)
5207953-3-ND
571-5207953-3
1
$.50
Schottky Diode 20V 3A DO201AD  1N5820-E3/54  (To put inline with power wire)
1N5820-E3/54GICT-ND
625-1N5820-E3/73







Additional Optional Parts You May Want


Kapton tape for protecting the pins from the enclosure. (or use packaging tape)   D-Sub machined pins for the box connector (Pins such as 204370-8 or  MilSpec M39029/64-369 are not included in the above).  (Alternate Pin source: SteinAir SA-1018)  If you want to join any d-sub connectors shell to another mating connector, you may want these hex nuts Conec 160X10379X or Digi-Key 626-2113-ND.









GDL90_Converter_422r1.3_Board_Bottom.png
GDL90_Converter_422r1.3_Board_Bottom.png
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GDL90_Converter_422r1.3_Board_Bottom_Layer.png
GDL90_Converter_422r1.3_Board_Bottom_Layer.png
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GDL90_Converter_422r1.3_Board_Bottom_Silkscreen.png
GDL90_Converter_422r1.3_Board_Bottom_Silkscreen.png
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GDL90_Converter_422r1.3_Board_Bottom_Soldermask.png
GDL90_Converter_422r1.3_Board_Bottom_Soldermask.png
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GDL90_Converter_422r1.3_Board_Drills.png
GDL90_Converter_422r1.3_Board_Drills.png
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GDL90_Converter_422r1.3_Board_Top.png
GDL90_Converter_422r1.3_Board_Top.png
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GDL90_Converter_422r1.3_Board_Top_Layer.png
GDL90_Converter_422r1.3_Board_Top_Layer.png
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GDL90_Converter_422r1.3_Board_Top_Silkscreen.png
GDL90_Converter_422r1.3_Board_Top_Silkscreen.png
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GDL90_Converter_422r1.3_Board_Top_Soldermask.png
GDL90_Converter_422r1.3_Board_Top_Soldermask.png
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