Faxitron MX-20 Reverse engineering (with some good results)

[kilohercas]

I started to make my own electronics for Faxitron MX-20 Machine. I only get electronics, X-Ray generator and X-Ray sensor, so I have to put something inside my won box.

I don't have software of any kind, so i have to write my own. First step was to make USB Hub, one channel wil go to sensor, second channel to FT2232H Controller as UART ( and second IC channels goes to stepper drivers for CBCT turning table)


After that, i had to write my own software for Hamamatsu 12x12 X-Ray sensor. That was quite a difficult task, but i was able to make it happen. I was able to do that in Visual Basic, it uses generic Hamamatsu DCAM-API DLL inside system32 (when you install drivers)



Operation is simple. Connect USB to HUB, it detects if FT2232H and C9732DK-11, after that, you wait for 60s warmup ( x ray tube or something, timer is inside x ray controller ) And you just set  time and kV, and press take  a picture. It automatically sends command to enable x ray source, you should (2.5s is ramp-up to 35kV, only at this point  x ray is stable based on sense output on x ray tube)
put into remote mode: (do this first !!!!)
                Dim mx20(5) As Byte '
                mx20(0) = &H21
                mx20(1) = &H4D
                mx20(2) = &H52
                mx20(3) = &HD
                PORT.Write(mx20, 0, 4)


This is how you set exp time and voltage:

            mx20(0) = &H21
            mx20(1) = &H54
            mx20(2) = &H30 + Fix(NumericUpDown1.Value / 100)' time 0.1 to 999.9
            mx20(3) = &H30 + Fix(NumericUpDown1.Value / 10) Mod 10
            mx20(4) = &H30 + Fix(NumericUpDown1.Value) Mod 10
            mx20(5) = &H30 + ((NumericUpDown1.Value * 10) Mod 10)
            mx20(6) = &HD
            UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 7, BW)
            Sleep(100)
            mx20(0) = &H21
            mx20(1) = &H56
            mx20(2) = &H30 + Fix(NumericUpDown2.Value / 10) ' Voltage 10-35
            mx20(3) = &H30 + NumericUpDown2.Value Mod 10
            mx20(4) = &HD '

Enabling X-Ray source via UART message is also easy, just few special characters: '0x21+0x42+0x0D  and after short delay 0x43
                mx20(0) = &H21
                mx20(1) = &H42
                mx20(2) = &HD
                UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 3, BW)
                Sleep(50) ' 50ms Delay
                mx20(0) = &H43
                UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 1, BW)

It was so bad design to put 500W power supply, it even needs load to work. That is madness. All you need is isolated 24V 1A for x ray ( it is uses all interlocks, and is enabled by relay on J7 connector )
12V 1.3A     (main electronics)
-12V 0.05A (opamps +RS232 ?)
5V 0.5A       (MCU electronics)
5V 5A          (Hamamatsu sensor)

Now, controller electronics looks old, and very complicated. Since i will be using computer, it would be better just connect x ray head to my own electronics, so i spend all tay figuring out controller connector to x ray source.

It is IDC20, and it has control, sense and other signals prescient, just have to figure out what is what.

IDC20 pins 1,2,3,4,12,13 are connected to opamp outputs inside x-ray head electronics. I only understand that 12pin is kV sense output to MCU board (1v=10kV), and 3pin is I sense, or it looks like this, with transfer function of:

10kV-> 0.208mA -> 0.61V
15kV-> 0.201mA -> 0.90V
20kV-> 0.192mA -> 1.19V
25kV-> 0.183mA -> 1.46V
30kV-> 0.175mA -> 1.76V
10kV-> 0.165mA -> 2.05V

IDC20 10PIN is also strange, MCU is supplying voltage, with a transfer function of ( every time, not only when x-ray is on)
10kV = 1.330V
20kV = 2.333V
30kV = 3.116V
35kV = 3.548V
Update: It has something to do with focusing. disconnecting yield blurry images. Maybe could be tuned separately for better picture, so must keep on DAC.

For output that change state when x ray is on, i have few of them:
PIN5 is connected to MCU via 330R  resistor ( mcu supplying 5V when enabling x ray )
PIN7 is connected to MCU via 2k2    resistor ( mcu supplying 5V when enabling x ray , another 12V relay for 24V that is main power for HV supply)
PIN9 is connected to DAC that supplying setpoint voltage from 1V (10kV) to 3.5V (35kV ) again, only when x-ray is on.
PIN11 is connected to DAC, it is supplying 2.7V only when x-ray is on (no mater on set voltage or time)

PIN10 looks like getting 10V from x-ray head, it is connected to potentiometer top input on high voltage power supply. still need to figure out why.
PIN15 and PIN17 is unconnected ( hooray:) )

PIN 14, PIN18, PIN19, and PIN20 are ground

Now I have to try to make my own driver on simple PCB, and we will see how it works. This will enable to buy MX-20 systems on ebay, and just ask to send sensor and x ray source, and i will be able to control everything

This post is mainly to remind myself, what i did so i don't loose it

[eliocor]

What software will you use/are you using for CBTC (Cone beam computed tomography) ?

[kilohercas]

MATLAB.

But it also would be fun to write my own in C/vb

[kilohercas]

few weeks of hard work, and i have complete solution for reading data from sensor as well as controlling x ray tube with my own driver that is based on Intel max10 fpga, works like a charm

[jeremy]

Very cool!

[kilohercas]

https://youtu.be/HrUNLFlLzzU

[jeremy]

What was the USB hub for? I couldn’t quite tell. I know you have an FTDI, but what else?

Also, is there any reason you decided to use an FPGA over a micro?

Would love to know more about how the panel outputs data and in what format.

Edit: ah I see now, the detector is USB connected.

[KE5FX]

Awesome work, would love to hear more.

My MX-20 has the older RadEye sensors, so I had to do a lot more work to get data out of them.  I would very much like to make my software talk to the control panel.  I don't understand what you mean here:

                mx20(0) = &H21
                mx20(1) = &H42
                mx20(2) = &HD
                UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 3, BW)
                Sleep(50) ' 50ms Delay
                mx20(0) = &H43
                UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 1, BW)

Are these instructions interpreted by your firmware, or passed to the Faxitron's controller?  If they're handed off to the Faxitron and processed there, how do you connect your controller to the Faxitron's CPU?

I don't currently have a UART available via the USB connection to my digitizer, but I could add one easily enough, if I knew where to connect it to the Faxitron.

[kilohercas]

Are these instructions interpreted by your firmware, or passed to the Faxitron's controller?  If they're handed off to the Faxitron and processed there, how do you connect your controller to the Faxitron's CPU?

UART is connected to faxitron controller, this series of commands will trigger x ray source for fixed amount of time

I made project in hackaday.io https://hackaday.io/project/52104-x-raying-rose-in-30kev-in-high-resolution you will be able to find all information about this project, with design files so you can make it yourself

If you can, please share this video tomorrow, since it since, and it kind a looks beautiful Lets make it as viral video for tomorrow

[KE5FX]

I made project in hackaday.io https://hackaday.io/project/52104-x-raying-rose-in-30kev-in-high-resolution you will be able to find all information about this project, with design files so you can make it yourself

Thanks!  Looks promising.   (Edit, having watched the video, it looks fantastic!)

Unfortunately I don't seem to be able to open the .rar files with WinZip -- it says they're invalid.  Can you post ordinary .zip files additionally/instead?

I would prefer to create a remote-control link to the MX-20's existing control panel, but your work on the new PCB is certainly impressive.  Agreed that the power supply they used is ridiculous.  Mine has a large wirewound resistor that does nothing but provide the minimum load and dissipate heat.

[eliocor]

Unfortunately I don't seem to be able to open the .rar files with WinZip -- it says they're invalid.  Can you post ordinary .zip files additionally/instead?

update your WinZip with the latest version...
Otherwise go to https://www.rarlab.com/download.htm and download WinRar: the archives have no problems at all!!!

[Mr. Scram]

I'd love to get my hands on a tool like that. That looks absolutely amazing and very useful.

[KE5FX]

I'd love to get my hands on a tool like that. That looks absolutely amazing and very useful.

That Hamamatsu panel is... enviable.    Some zero-feedback scammer is currently trying to sell 10 of them on eBay for $10,000 apiece.

Although it sounds like it's limited to <2 second exposure times if I understand the video correctly?  With my RadEye sensors I often have to take 20-30 second exposures, but maybe that's not necessary with the C9732DK. 

[mikeselectricstuff]

I'd love to get my hands on a tool like that. That looks absolutely amazing and very useful.

That Hamamatsu panel is... enviable.    Some zero-feedback scammer is currently trying to sell 10 of them on eBay for $10,000 apiece.

Although it sounds like it's limited to <2 second exposure times if I understand the video correctly?  With my RadEye sensors I often have to take 20-30 second exposures, but maybe that's not necessary with the C9732DK.

My Faxitron ( with 50mm Hamamatsu sensor) does up to 15 sec exposures. Not sure if extending would have much benefit due to noise floor. A few more kV would be much more useful.
The tube is rated to 50kV, but the sensor datasheet states 35kV max - would be interesting to know what the actual constraints are, as the limited penetrating power is the biggest disappointment of this system.

Where does the 2 sec limit come from ?

I don't understand the reason for replacing the faxitron control electronics - is there any benefit ?
Are you still using the original cabinet or were you re-packaging to reduce size?

[kilohercas]

Where does the 2 sec limit come from ?

I don't understand the reason for replacing the faxitron control electronics - is there any benefit ?
Are you still using the original cabinet or were you re-packaging to reduce size?

It comes from sensor, it has double value between 1  and 2. higher exposures are just stitched images made from 2s exposures i think. (DLL takes that data)

I only get detector and x  ray tube, that's why i am remaking it myself. Also, i have greater control over tube voltage, have diagnostics about tube voltage/current, so i can decide then to take picture, and stop x ray after that. I will also planing to add mechanical shutter, if i will try to x ray my hands, just to get dose down. Same goes for stepper control and other automation. this is very powerful system now, i even can think about chaining sensor position with other stepper to get different magnification

Also, electronics are old, if they break, i loose everything, now i know half the system, so less chance of failure

It can work with 100kV. In my work, i get visit from Hamamatsu, he says that problem with energy and power is that CsI will get yellow in time, but that's not a problem, since we still have so much data to work with, and we could use higher exposure times to get higher pixel values, so detector will be good for a long time.

[KE5FX]

My Faxitron ( with 50mm Hamamatsu sensor) does up to 15 sec exposures. Not sure if extending would have much benefit due to noise floor. A few more kV would be much more useful.
The tube is rated to 50kV, but the sensor datasheet states 35kV max - would be interesting to know what the actual constraints are, as the limited penetrating power is the biggest disappointment of this system.

I was able to crank the HV trimmer up to get 37.015 kVp at 325 uA out of mine.  The PSU folds back either current or voltage once the total power exceeds 12 watts, which is a good match for the maximum-rating spec of the TruFocus tube.

Where does the 2 sec limit come from ?

Linas mentioned on his Hackaday page that the Hamamatsu sensor has "very limited range, only between 1 and 2 seconds of integration."

I don't understand the reason for replacing the faxitron control electronics - is there any benefit ?

From my own perspective, I'd like to be able to set the voltage and exposure time from the software and trigger it remotely.  I often take bracketed exposures at different settings, looking for the best compromise for a given subject.  It'd be nice if I didn't have to punch a lot of buttons every few seconds, or keep track of the resulting image settings manually. 

The original Faxitron software could also carry out automatic calibration exposures, which I'd like to implement in my own software at some point.

[mikeselectricstuff]

From my own perspective, I'd like to be able to set the voltage and exposure time from the software and trigger it remotely.  I often take bracketed exposures at different settings, looking for the best compromise for a given subject.  It'd be nice if I didn't have to punch a lot of buttons every few seconds, or keep track of the resulting image settings manually. 

You can do that via the serial interface

[KE5FX]

From my own perspective, I'd like to be able to set the voltage and exposure time from the software and trigger it remotely.  I often take bracketed exposures at different settings, looking for the best compromise for a given subject.  It'd be nice if I didn't have to punch a lot of buttons every few seconds, or keep track of the resulting image settings manually. 

You can do that via the serial interface

I didn't exactly see any 9-pin RS232 ports on mine.  

I'm sure the necessary serial lines were brought out to the SCSI-style connector on the rear panel, but that's long gone.  Have you run across any documentation for their command set?

[mikeselectricstuff]

From my own perspective, I'd like to be able to set the voltage and exposure time from the software and trigger it remotely.  I often take bracketed exposures at different settings, looking for the best compromise for a given subject.  It'd be nice if I didn't have to punch a lot of buttons every few seconds, or keep track of the resulting image settings manually. 

You can do that via the serial interface

I didn't exactly see any 9-pin RS232 ports on mine.  

I'm sure the necessary serial lines were brought out to the SCSI-style connector on the rear panel, but that's long gone.  Have you run across any documentation for their command set?

I'm not familar with all the variants - I assumed they all had remote control, but as these units were probably originally designed for film, maybe not.

[KE5FX]

From my own perspective, I'd like to be able to set the voltage and exposure time from the software and trigger it remotely.  I often take bracketed exposures at different settings, looking for the best compromise for a given subject.  It'd be nice if I didn't have to punch a lot of buttons every few seconds, or keep track of the resulting image settings manually. 

You can do that via the serial interface

I didn't exactly see any 9-pin RS232 ports on mine.  

I'm sure the necessary serial lines were brought out to the SCSI-style connector on the rear panel, but that's long gone.  Have you run across any documentation for their command set?

I'm not familar with all the variants - I assumed they all had remote control, but as these units were probably originally designed for film, maybe not.

I'm sure that it can be controlled remotely because this particular unit came with its manuals.  There is a variant of the usual MAX232 interface IC on the controller board, so it wouldn't be hard to trace its pins through the cable that formerly went to the external connector.   But the manuals have no information on how the low-level communication with the PC worked, and disassembling the firmware would consume more time than it'd be worth.

[mikeselectricstuff]

From my own perspective, I'd like to be able to set the voltage and exposure time from the software and trigger it remotely.  I often take bracketed exposures at different settings, looking for the best compromise for a given subject.  It'd be nice if I didn't have to punch a lot of buttons every few seconds, or keep track of the resulting image settings manually. 

You can do that via the serial interface

I didn't exactly see any 9-pin RS232 ports on mine.  

I'm sure the necessary serial lines were brought out to the SCSI-style connector on the rear panel, but that's long gone.  Have you run across any documentation for their command set?

I'm not familar with all the variants - I assumed they all had remote control, but as these units were probably originally designed for film, maybe not.

I'm sure that it can be controlled remotely because this particular unit came with its manuals.  There is a variant of the usual MAX232 interface IC on the controller board, so it wouldn't be hard to trace its pins through the cable that formerly went to the external connector.   But the manuals have no information on how the low-level communication with the PC worked, and disassembling the firmware would consume more time than it'd be worth.

A while ago I grabbed a dump of the serial comms - it was pretty simple & obvious ASCII - will see if I can find it

[KE5FX]

A while ago I grabbed a dump of the serial comms - it was pretty simple & obvious ASCII - will see if I can find it

Thanks, that could come in very handy.  I'm mostly interested in starting/stopping the exposure and setting the kVp.  The ability to set the exposure time would be good as well, but the PC could emulate that if necessary.

[kilohercas]

A while ago I grabbed a dump of the serial comms - it was pretty simple & obvious ASCII - will see if I can find it

Thanks, that could come in very handy.  I'm mostly interested in starting/stopping the exposure and setting the kVp.  The ability to set the exposure time would be good as well, but the PC could emulate that if necessary.

Have you try to look at the first post ? All of this information is detailed. only stop function is missing...

[KE5FX]

Have you try to look at the first post ? All of this information is detailed. only stop function is missing...

That doesn't do me any good if I don't use your hardware, does it?  I already have a working system that I don't want to change to that extent.  I'd just like to be able to send remote commands to the original Faxitron controller.

That's basically why I was asking if your serial code was communicating with the original hardware or with your own controller.

[kilohercas]

Have you try to look at the first post ? All of this information is detailed. only stop function is missing...

That doesn't do me any good if I don't use your hardware, does it?  I already have a working system that I don't want to change to that extent.  I'd just like to be able to send remote commands to the original Faxitron controller.

That's basically why I was asking if your serial code was communicating with the original hardware or with your own controller.

put into remote mode: (do this first !!!!)
                Dim mx20(5) As Byte '
                mx20(0) = &H21
                mx20(1) = &H4D
                mx20(2) = &H52
                mx20(3) = &HD
                PORT.Write(mx20, 0, 4)


This is how you set exp time and voltage:

            mx20(0) = &H21
            mx20(1) = &H54
            mx20(2) = &H30 + Fix(NumericUpDown1.Value / 100)' time 0.1 to 999.9
            mx20(3) = &H30 + Fix(NumericUpDown1.Value / 10) Mod 10
            mx20(4) = &H30 + Fix(NumericUpDown1.Value) Mod 10
            mx20(5) = &H30 + ((NumericUpDown1.Value * 10) Mod 10)
            mx20(6) = &HD
            UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 7, BW)
            Sleep(100)
            mx20(0) = &H21
            mx20(1) = &H56
            mx20(2) = &H30 + Fix(NumericUpDown2.Value / 10) ' Voltage 10-35
            mx20(3) = &H30 + NumericUpDown2.Value Mod 10
            mx20(4) = &HD '

Enabling X-Ray source via UART message is also easy, just few special characters: '0x21+0x42+0x0D  and after short delay 0x43
                mx20(0) = &H21
                mx20(1) = &H42
                mx20(2) = &HD
                UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 3, BW)
                Sleep(50) ' 50ms Delay
                mx20(0) = &H43
                UART_Status = FT_Write_Bytes(UART_Handle, mx20(0), 1, BW)

This is serial to original controller