Help with interface board for RDAC X-B

[eengineer]

I received RDAC X-B as a gift.
But for some reason the equipment is different from those that I find in the photo on the Internet.
It's as if there is no interface board.
https://support.michiganavionics.com/po ... -xd-manual

three

RDAC_X_B.jpeg (179.21 KiB) Viewed 251 times

I disassembled the case, powered the LDO(L7805) with 9 volts and do not receive any data via the RS-232 protocol

two

photo1713123931.jpeg (104.25 KiB) Viewed 251 times

I had another RDAC Vb module, so I power it with 9 volts in the same way, and it outputs data about the PC-232 protocol to the Stratomaster Ultra Horizon XL device.
And when I connect the motor to the RDAC Vb block, I can see the number of revolutions on the Stratomaster Ultra Horizon XL device.
https://www.stratomaster.eu/desktopdefa ... &tabid=188

one

photo1713123931 (2).jpeg (91.68 KiB) Viewed 251 times

I would like to figure it out and, if necessary, repair the RDAC X-B.
Help with advice.

[rainier]

Is your LED on the RDAC flashing ?

[eengineer]

Is your LED on the RDAC flashing ?

The problem is that the LED does not light up and does not blink at all.
Although +5V power is supplied to the board and the MCU.
Perhaps the microcontroller has become unusable, but I can replace it, but I couldn’t find the firmware anywhere.
I can write my own code for MCU, but all the functions of the device will not be implemented as intended.
I also discovered that the inductor was burning, but overall it is still working.

Coil_burned.jpeg (174.8 KiB) Viewed 230 times

I'm trying to ring all the circuits on the board and draw them in the diagram to make it clear and convenient to look for a fault.

MCU_LED.png (25.13 KiB) Viewed 230 times

I haven't connected anything to the board's periphery yet.
As far as I understand from the documentation on the RDAC-Xb, when power is applied, the LED should blink, indicating a lack of communication.

Board.png (58.55 KiB) Viewed 230 times

But, as I wrote above, it feels like the bottom board, on which there were connectors and contacts for connecting sensors, has disappeared.
I wonder what format the protocol uses to transmit data.
Everywhere it is written that this is a RS232 protocol.
Please tell me, Can I receive data via a USB-TTL converter?
https://www.mglavionics.co.za/Docs/RDAC ... otocol.pdf
I would really appreciate your help.

[rainier]

The LED will flash at 1Hz when the CPU is running.

If you have supply voltage at the CPU, the reset line is logical high, I'd be pretty sure that CPU is history - if you can find a replacement (make sure it is exactly the same) contact me privately and I'll send you the binary to flash to the CPU. You will also have to do some calibration and I'll tell you how to do that. You will need a 24.9mV DC supply for that (low impedance or a resistive divider and multimeter to confirm correct voltage).

Rainier

[eengineer]

The LED will flash at 1Hz when the CPU is running.

If you have supply voltage at the CPU, the reset line is logical high, I'd be pretty sure that CPU is history - if you can find a replacement (make sure it is exactly the same) contact me privately and I'll send you the binary to flash to the CPU. You will also have to do some calibration and I'll tell you how to do that. You will need a 24.9mV DC supply for that (low impedance or a resistive divider and multimeter to confirm correct voltage).

Rainier

On the pin of the PC6/RESET microcontroller there is 4.5 volts, which corresponds to logical 1.
Below is a diagram that I was able to draw from the board.

Schematic.png (25.49 KiB) Viewed 165 times

I still think this microcontroller(ATmega88-20A) is fine

photo_ATmega88-20A.jpeg (115.03 KiB) Viewed 159 times

but I also bought a similar replacement, if there is firmware, I can download it.
As far as I understand, from the output of PD1 (TXD), the data received by the microcontroller and converted into the MGL protocol is supplied in UART format to an optotransistor, and data can be obtained from the PL2 connector.

ATmega88-20A.png (104.03 KiB) Viewed 165 times

But unfortunately, I didn’t have an interface board with convenient terminals in the kit.
P.S.
I wrote to you in a personal message.