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Bill Of Materials
Updated 20 January 2025
Details on parts to build your own. Under construction. A full BOM with part numbers and links will be posted after the PCB is built and design finalized. Boards and a range of parts were ordered on January 20.
I have designed a 120mm x 74mm PCB sized to slide into Hammond 1455J1202BK aluminum box. It has 8 LEDs on the PCB. You will have to make holes in the end plates for the connectors and drill 8 holes for the LED's light pipes positioned over those LEDs. I decided to use 8 LEDs for status rather than an OLED display, but one can be added later using the ic2 bus connector on the PCB.
As long as the ESP32-S3 CPU module of choice has enough output pins, either natively or through an i2c extender module, and it has at least one USB port that supports OTG, it should be usable.
Below is the link to specs that match the clone ESP32-S3-DevKitC-1 N16R8 board I got online, 3 for $18. Not using the PSRAM so can use a lesser version. The N8 version with no PSRAM should work as well. The current image size is only 354Kbytes. The 32K version (N32R8) is a bit different but might also work.
https://mischianti.org/vcc-gnd-studio-yd-esp32-s3-devkitc-1-clone-high-resolution-pinout-and-specs
The SPI PSRAM is not enabled by default. If it was, it would use pins 35, 36, 37. 2 of those I am using for LEDs due to the physical location of the pin vs LED mounting point. The LEDs would have to move to alternate available pins if PSRAM. The onboard RGB is powered off 5V on this clone board, not 3.3V as the original board does.
You can choose to have no display or indicators. I support 8 programmable and dimmable LEDs by default and designed teh PCB to use them. With some relatively simple code added, an SSD1306 OLED can be used. The color LCD in the M5AtomS3 is already working though you have to extend the IO to make it do anything useful for our band decoder. You can add in your own display code if you want something different. At startup I poll the radio for frequency, mode, extended mode, time, location, and UTC offset. I calculate the current grid square to 8 digits. It is shown in the debug and on the M5 AtomS3 display.
** IO pins
There is no reason you can't change the total number of IO pins as long as your hardware has free pins available. Adding 2 more pins to each group of 6 pins (Band Select and PTT groups) is the easiest to do since the patterns are represented in 1 byte values. There is a different project for using the 905 with a transverter. Adding another group of 8 would be the next step. I have other Band decoder projects that already support more pins, on several IO devices, but this project is a more targeted and simplified project starting out with 6 pins per group to match the IC-905's 6 bands. It also needs to be set to something well defined to work on a PCB.
The PCB has been designed and ordered, waiting for it to arrive and be tested. A schematic and PCB layout will be published along with the full list of parts needed for the PCB version. There are 2 PCBs, the main USB Decoder and a new optional board I call the Remote BCD decoder which is general purpose and can be used to reduce the cabling required between the USB decoder and a RF unit located a long distance away.
For now here is a simple list:
1x ESP32-S3-DevKitC-1 - Clone used here, was easy to add the 5V USB host power with a resistor.
2x 2.1mm x 5.5mm power coaxial jacks
1x LM78L05 5V regulator
1x 1N4007 diode for power to 5V regulator
1x 0.15A resettable fuse on input to 5V
Xx 0.1pF caps for the regulator and connector inputs
1x 10uf 6V electrolytic cap for the brightness pot.
1x 22uF or greater 16V electrolytic cap for the regulator output
1x 1K 0805 size SMD resistor, soldered across the DevKitC-1 5v and USB Host Vbus isolation diodes to supply 5V to the USB host cable
1x Right angle Phono jack for PTT
1x green LED, 3mm
1x red LED, 3mm
6x blue LEDs, 3mm
1x 10K PCB mount pot
2x ULN2803A octal drivers
1x 1N914 diodes for pullup
7x wire jumpers and/or 0ohm 1206 resistors
1x PCB
1x resistor for PTT input pullup
8x LED light pipes, 1/2" for 3mm LEDs.
2x 1A resettable fuse for 12V or 24V to the relays/preamps
1x Optional 24V DC-DC converter to power a few 24V relays (externally mounted)
1x right angle PCB mount HD 15-pin female D-Sub connector (aka VGA connector)
1x right angle 4 pin header for power in and out of the external DC-DC converter, if used
1x 1/8" stereo headphone jack (not used today - for possible future CI-V USB to analog bridging feature)
1x Plastic or aluminum case, drilled for the LEDs and end panel connectors - Hammond 1455J1202BK to fit the PCB
Cable lengths here are assuming the decoder is to be mounted on the top or back of the 905 controller. Otherwise adjust the length of the cables to suit your needs.
1x Mounting bracket of some sort. Hammond has optional mounting tabs.
1x 6" DC power cord with 2.1x5.5 coaxial power plugs to connect radio to box
1x 6" PTT cable, 1/8" stereo plug on one end, phone plug on the other, tip and ground. ring not used.
1x 6" USB Type C to Type C cable. Suggest one or more snap-on ferrites be snapped on.
1x HD 15-pin male D-Sub plug connector. I like to use the breakout version which offer 16 green micro terminal strips inside the cover, no soldering required
The Remote BCD Decoder board will be on a separate page.