Reprap Forum - Controllers

Need some help identifying and configuring an old controller board.

Mart7 — Fri, 30 Jan 2026 18:11:20 -0500

Hi,

I've come across an old board, I think it's a Tronxy P802MA based on melzi:

However I've flashed marlin and klipper to the board, but I simply cannot get the endstops on x/y working, without knowing exactly what board I'm working with, it's a bit of a struggle to make sure I have the right pins, or I'm dealing with a hardware failure.

I'm on klipper at the moment and the configs I am use are:

[stepper_x]
step_pin: PD7
dir_pin: PC5
enable_pin: !PD6
microsteps: 16
rotation_distance: 32
endstop_pin: PC2
position_endstop: -8
position_max: 220
position_min: -45
homing_speed: 50

[stepper_y]
step_pin: PC6
dir_pin: PC7
enable_pin: !PD6
microsteps: 16
rotation_distance: 32
endstop_pin: ^PC3
position_endstop: 0
position_min: -5
position_max: 220
homing_speed: 50

I've tried various combos of reversing logic or using pull up to no avail

I'm getting 4.9v at the pull up resistor in front of the endstop socket, but S+G is only seeing 2.8v - V+G is seeing 12v

The Z endstop is working fine, S+G showing 5.5v dropping when closed

PS: you may need to zoom in on image to see where I took voltage readings

thanks

Re: MKS Robin Nano V3.1 flashing via USB?

Flyer2000 — Fri, 19 Dec 2025 05:25:23 -0500

"But note in that mode you can easily brick the board or over write the boot loader"

Yes, those are my concerns too. That's why I haven't experimented with it yet. :S

Re: MKS Robin Nano V3.1 flashing via USB?

Dust — Thu, 18 Dec 2025 17:27:40 -0500

In theory you can use DFU mode

But note in that mode you can easily brick the board or over write the boot loader

This need access to the the boot and reset pins

MKS Robin Nano V3.1 flashing via USB?

Flyer2000 — Thu, 18 Dec 2025 17:13:53 -0500

Hello everyone,
I have an new MKS Robin Nano V3.1 board. Is there a way to flash the board via USB?
I would like to use a command-line tool (bossac or similar) for this. The onboard media (USB/SD card slot) are no longer accessible after installation.

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

Henrique — Sat, 19 Jul 2025 15:47:14 -0400

OK. Sorry. It is the Power Supply.

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

VDX — Sat, 19 Jul 2025 15:46:24 -0400

... PS = Power-Supply or -Source

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

Henrique — Sat, 19 Jul 2025 15:19:20 -0400

Sorry, but I could not understand what you meant PS?
Thanks!

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

VDX — Sat, 19 Jul 2025 13:02:47 -0400

... if it's lack of current, then a "stronger" PS will help B)-

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

Henrique — Sat, 19 Jul 2025 07:53:51 -0400

Ok, thank you.
I understood.
But is there a way to keep the 5V level constant? Even after the printing starts?
I believe that this blue screen starts after the BLTouch pins down.
But even with the blue screen lighted, the printing begins and goes up to the end.
I am still asking myself how to keep this 5V level.

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

VDX — Sat, 19 Jul 2025 05:44:30 -0400

... there should be several pins, marked with "+5" and "GND" -- connect a multimeter and look, if the 5V level drops, if printing starts ... most likely with unsufficient current from the PS

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

Henrique — Fri, 18 Jul 2025 18:10:25 -0400

I dont know where to measure this.
Is there a pin at ramps?

Re: Reprap Discount Full Graphic LCD Controller - Blue Screen

VDX — Fri, 18 Jul 2025 16:21:42 -0400

... can you measure the +5V for the controller, if it breaks down?

Reprap Discount Full Graphic LCD Controller - Blue Screen

Henrique — Fri, 18 Jul 2025 15:33:14 -0400

Hi everyone!

I have a Full Graphic LCD Controller that starts blue screen after the print starts.
Before comanding the print, the screen shows the status normally.
Bul after the print starts, the blue screen appears.
Sometimes starnge caracthers appear at any moment.
Does anybody know how to fix this?
Thanks!

Re: Unstable temp reading [MKS GenL]

andry_ad — Tue, 25 Feb 2025 20:35:21 -0500

Had the same issue with a MKS Gen L v1.0 which resulted in thermal runway/nozzle temp fluctuations in Tevo Tornado. I was able to fix it with replacing C11 with 330uF Low ESR capacitor (Panasonic FR Series Electrolytic Capacitors - 35V 330uf 20% Ultra Low ESR from Amazon) - huge thanks to @Batam, @Primsam, @Surenz. I have had 20 hours of printing since the fix and no issues so far.
I used the same steps as @Moff_Tigriss(thanks!) described to validate the issue:
1) power the board from usb only - nozzle temp is stable (usually one degree in either direction)
2) switch to main power - nozzle temp unstable (we're talking +-5 degrees fluctuation between values within a second)
3) power + usb - same result as #2

What's interesting, I had no issues up until recently and I owe the printer for multiple years. The most recent upgrade I did was to move to TMC 2209 but I successfully printed almost three spools before my printer started to give me thermal runaway E1 error on a constant basis. Maybe it happened right after I upgraded to TMC2209 drivers and I didn't notice or maybe it's just a coincidence - not really sure.

If you decide to do this fix, don't forget to check a polarity (black size on old cap is negative and it was white stripe on the Panasonic one) and do PID autotune afterwards. Replacing the cap is a bit tricky - I actually destroyed the old one in process - smd pads go under the cap and only small part is visible so it's a pain to desolder. I didn't disassemble the board to replace the capacitor.

We still use this board in 2025. GL next guy :D

Re: Bigtreetech SKR 1.4 Turbo with Thermocouple

RobertEdgar — Tue, 25 Feb 2025 01:05:07 -0500

Quote
BlakeUnderwood
Quote
brucehvn
Ok, I gave up on trying to get the AD595 board working. I had a AD8495 board laying around I had forgotten about, but it turns out it appears it was bad as I could not get the proper readings from it, even just testing the ambient temperature without it being connected to the printer.

I broke down and bought a MAX31855 board. I have a configuration that I believe is working with that except it causes me to lose the ability to see my SKR card as a USB device on my print server so I can copy the firmware easily which with as many changes as I'm making to the firmware right now is a big deal.
I've been experimenting with various op-amps for my DIY 3D printer controller, and one challenge has always been finding reliable low-power, high-precision options for signal processing. I recently came across the MCP602T-I/SN, which offers low bias current and rail-to-rail output—perfect for precision applications. I sourced it from Ovaga, where they provide detailed specs and availability. It has significantly improved signal integrity in my setup. Has anyone else used this op-amp in their 3D printing projects? Would love to hear your thoughts!
FIrst I had the MAX board hooked to the SPI header on the board. I used pin 0.26 as the CS pin and the SCLK and MISO pins on the header. This didn't work until I set:
#define SDCARD_CONNECTION ONBOARD
Which then caused my ambient temperature to show up correctly, but I lost my USB functionality for my SD card and I could not use the LCD's SD card slot (reprap full graphic discount controller).

I then used the same pins, but defined the MISO and SCLK in configuration_adv.h which according to the comments should throw it into software SPI mode. I set the SDCARD_CONNECTION to LCD and I still was reading a temperature, and I could see the SD card on the LCD with all my GCode files, but still no USB support for the firmware SD Card.

Currently, I'm trying to use the SPI pins on the unused E1 driver slot, but that doesn't seem to work at all. Printer gives an immediate MINTEMP error and halts.

So, I'm confused about a few things. If I want to use Software SPI for the temperature probe, can I specify any open pins, or do they have to be ones designated for SCLK and MISO? I know I can specify any pins for the CS pin.

On this particular board, it looks to me like there are 2 hardware SPI ports surfaced at the SPI header and the EXP connectors where the LCD is attached. The ones in the printer driver pins aren't designated in the processor datasheet as actual SPI pins, but somehow get used as that on the board. Am I correct on those things?
I had the same problem.

How is everything now?

Re: Bigtreetech SKR 1.4 Turbo with Thermocouple

BlakeUnderwood — Mon, 10 Feb 2025 01:03:50 -0500

Quote
brucehvn
Ok, I gave up on trying to get the AD595 board working. I had a AD8495 board laying around I had forgotten about, but it turns out it appears it was bad as I could not get the proper readings from it, even just testing the ambient temperature without it being connected to the printer.

I broke down and bought a MAX31855 board. I have a configuration that I believe is working with that except it causes me to lose the ability to see my SKR card as a USB device on my print server so I can copy the firmware easily which with as many changes as I'm making to the firmware right now is a big deal.

FIrst I had the MAX board hooked to the SPI header on the board. I used pin 0.26 as the CS pin and the SCLK and MISO pins on the header. This didn't work until I set:
#define SDCARD_CONNECTION ONBOARD
Which then caused my ambient temperature to show up correctly, but I lost my USB functionality for my SD card and I could not use the LCD's SD card slot (reprap full graphic discount controller).

I then used the same pins, but defined the MISO and SCLK in configuration_adv.h which according to the comments should throw it into software SPI mode. I set the SDCARD_CONNECTION to LCD and I still was reading a temperature, and I could see the SD card on the LCD with all my GCode files, but still no USB support for the firmware SD Card.

Currently, I'm trying to use the SPI pins on the unused E1 driver slot, but that doesn't seem to work at all. Printer gives an immediate MINTEMP error and halts.

So, I'm confused about a few things. If I want to use Software SPI for the temperature probe, can I specify any open pins, or do they have to be ones designated for SCLK and MISO? I know I can specify any pins for the CS pin.

On this particular board, it looks to me like there are 2 hardware SPI ports surfaced at the SPI header and the EXP connectors where the LCD is attached. The ones in the printer driver pins aren't designated in the processor datasheet as actual SPI pins, but somehow get used as that on the board. Am I correct on those things?

I had the same problem.

Re: BTT SKR 1.4 Turbo with MKS TS35

ajeje brazorf — Sat, 31 Aug 2024 09:41:25 -0400

You're right but as I said I changed the cable on the screen as in the image. For the software part I have alredy tried all the configuarations that I found searching for this problem and none of them worked, I post the configuration too so you can see it and I hope that you can find something that I missed. The screen is always withe as in the second image and it flash a bit if the board is restarted. Thank you for your time and patience

Re: BTT SKR 1.4 Turbo with MKS TS35

Dust — Mon, 26 Aug 2024 11:40:19 -0400

no configs, no images of how you have it plugged in, no way to confirm or check anything.

Re: BTT SKR 1.4 Turbo with MKS TS35

ajeje brazorf — Mon, 26 Aug 2024 06:42:51 -0400

Hi, I have a problem with the same setup, I am using a SKR 1.4 and TS35 V2, I have alredy turned the cable plug of EXP and changed everything you said in this post but my screen only does withe sreen, I tried changing UI to classic, disabling touch and rewiring but nothing. If you can give some advice of how you made the screen work it woult be helpfull. Thanks again

Re: replacement for MKS Gen-2Z v1.1

3dby3d — Fri, 09 Aug 2024 15:26:30 -0400

I have switched to RAMPS 1.6 plus version but I cannot connect two stepper motors on the Z plug due to plastic configuration of the plug motor so, in the Marlin code I have uncomment line #define Z_DUAL_STEPPER_DRIVERS from the Configuration_adv.h and now the second motor is instead of E1.

Re: replacement for MKS Gen-2Z v1.1

Dust — Thu, 08 Aug 2024 03:58:02 -0400

the ramps dual z stepper motor plugs are on the 1 Z stepper driver in parallel.

When using two stepper drivers one stepper is plugged into either z plug and the second one is plugged into e1 stepper plug

Re: replacement for MKS Gen-2Z v1.1

3dby3d — Thu, 08 Aug 2024 03:33:52 -0400

I am planning to replace with a combination of MEGA 2560 and RAMPS 1.4 or 1.6 but I do not know how to make connections for Z axis with 2 stepper drivers. On both RAMPS boards on the Z location there are 2 pairs of 4 pins. Shall I insert the first stepper driver in the Z stepper driver location and the second one on the E1, and the 4 pins cables should be placed where ? ...both on the 2 Z pairs pins location or separately ?

Re: replacement for MKS Gen-2Z v1.1

Dust — Wed, 07 Aug 2024 19:07:36 -0400

If you tell marlin you have a Z2 stepper driver, Marlin automatically uses the first unused E (in this case E1) as Z2

replacement for MKS Gen-2Z v1.1

3dby3d — Wed, 07 Aug 2024 11:20:56 -0400

Hi, Usually most of the controllers have X,Y,Z ,E0 and E1. Mine has X,Y,Z1, E0 and Z2. How can I switch between these two controllers and what options in the firmware do I need to do to work ?

SSD1309 Oled 2.4" display

roman9999r — Tue, 28 May 2024 02:06:20 -0400

Hello.
I'm trying to get to work a graphic oled 2.42 inch display with my printer running Marlin 2.1.2.2 with Arduino Mega + Ramps 1.4.
The display has I2C and SPI capabilities, although the default is SPI.
I tried first with an Arduino board and after some trial and error I was able to make it work.
Besides the regular SPI signals (MISO, CLK & CS) needs two more signals Reset and DC.
As far as I could find, most configurations handle in the best case the CD signal but I was not been able to drive the reset properly. I tried most of the configurations available in Configuration.h but I got nothing in the display at all.

Any pointers?

Re: MKS GEN v1.4 Schematic

s_fr — Sat, 30 Mar 2024 08:43:25 -0400

Awesome!! Exactly what I was looking for. Thank you

Re: DIY Tiny OLED I2C full graphics controller

saniskycom — Wed, 14 Feb 2024 02:23:27 -0500

Configuration.h uncomment the line #define OLED_PANEL_TINYBOY2
#define ENCODER_PULSES_PER_STEP 2
And also:

#define ENCODER_NOISE_FILTER
#if ENABLED(ENCODER_NOISE_FILTER)
#define ENCODER_SAMPLES 10
#endif

AUX4 pins
31--ENC
33--BUZ
35--EN1
37--EN2

Re: DIY Tiny OLED I2C full graphics controller

rramirez — Sat, 10 Feb 2024 11:23:48 -0500

Greetings to all makers

MARLIN 2.1.2.1

I have a problem I hope you can help me, I am installing a tinyboy2 but I can not get it to work, with the statement in Configuration.h "#define OLED_PANEL_TINYBOY2" does not work at all, but if I change to "#define U8GLIB_SSD1306" the oled works correctly, but I can not use the encoder and buzzer to navigate through the menu, add the line in Conditionals_LCD.h ...

//} 128x64 I2C OLED LCDs - SSD1306/SSD1309/SH1106
#if ANY(U8GLIB_SSD1306, U8GLIB_SSD1309, U8GLIB_SH1106)
#define HAS_U8GLIB_I2C_OLED 1
#define HAS_WIRED_LCD 1
#define DOGLCD
+#define IS_ULTIPANEL 1
#endif

The encoder only works the central button to enter the menu but no pin in the AUX4 line does anything, I have checked it, I do not know if I need to assign pins in the ULTIPANEL section or I need to configure some other parameter, it should be noted that I am using the diagram published here, using the 4-pin I2C connector and AUX4 pins 31,33,35,37 for EN1,EN2,BTN,BEEPER, any comments or suggestions are welcome.

I will leave my code as I have it right now.

|Configuration.h|

//
// SSD1306 OLED full graphics generic display
//
#define U8GLIB_SSD1306

|Conditionals_LCD|

//} 128x64 I2C OLED LCDs - SSD1306/SSD1309/SH1106
#if ANY(U8GLIB_SSD1306, U8GLIB_SSD1309, U8GLIB_SH1106)
#define HAS_U8GLIB_I2C_OLED 1
#define HAS_WIRED_LCD 1
#define DOGLCD
+#define IS_ULTIPANEL 1
#endif

In pins_RAMP.h I don't have any parameter to configure ULTIPANEL only NEWPANEL, I am not very good at programming, I understand the most essential to configure marlin, I have already done it in 10 machines without any problem but this oled is causing me errors.

Re: RAMPS 1.4.4, RAMPS-FD, or RADDS

Progr3ss — Fri, 09 Feb 2024 22:02:02 -0500

Thank you for replying to me.

RADDS appears to have most of its stuff open source here RADDS. I acknowledge that I may be wrong.

Thanks for the tip about the RAMPS-FD, although I cannot find any of them for sale.

I saw the Re-Arm, but alas I don't think it is sold anymore. Seems interesting too, but didn't seem to be open source.

This last is the good part.
"But there is no point in this type of system anymore. Since there are now a lot of real 32bit boards properly designed readily available"
I am not finding any open source controllers that are not single board. What is a properly designed RAMPS shield style 32 bit board? What is a properly designed 32 bit shield with stepper drivers that can be changed? What is a properly designed board that is open source and can have parts replaced like the through hole of the RAMPS design?

That is what I am looking for.
Sorry if that was aggressive , I really do want you to respond. I am just trying to see what is still able to be made, not bought.
Scot

Re: RAMPS 1.4.4, RAMPS-FD, or RADDS

Dust — Fri, 09 Feb 2024 21:33:34 -0500

RADDS is not open source

RAMPS-FD (v1) was stolen by Chinese companies and mass produced, before it was finished, the mosfets are on by default! this is a fire hazard. Make sure you look at v2

these all use DUE which was never well received .

There is also the re-arm controller for a stock ramps board [reprap.org]

But there is no point in this type of system anymore. Since there are now a lot of real 32bit boards properly designed readily available