Controlling Yihua 995D for USB control

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I recently purchased a YIHUA 995D SMD Rework Station and me being the geek that I am wanted to see if I could perhaps control it (via USB/ATMEGA) by using my PC and touch screen instead of physically doing so with my hands. Being able to control it via PC would allow me to mount the 995D under my desk and out of sight so that I have more room to work with on the top of my desk.

However, I have limited knowledge on "snooping" or "Reverse Engineering" and that is why I am posting my project ideas here in hopes that someone more knowledgeable will be able to let me know what all I need to do in order to accomplish my task.

I started out thinking I would just simply hook up the ATMEGA and just control the buttons/knobs and leave everything else as-is and just use a webcam focus only on the LCD to view what was on. Although that would work, its not ideal nor is it geeky enough ;D .

The LCD screen seems to be controlled by the chip Holtek ht1621b. The website for it defines it as a "RAM Mapping 32x4 LCD Controller for I/O MCU". Here is the datasheet for it.

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There also seems to be another chip which seems to be the main MCU? It's called the S3 Microcontrollers u820 s3f8s19xzz-qr89 and it's datasheet.

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I've noticed that the IC above has a TX/RX UART line(s) looking at the diagram on page 9 of the datasheet.

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9.7 Port 4
Port 4 is an 8-bit I/O port with individually configurable pins. Port 4 pins are accessed directly by writing or reading the port 4 data register, P4 at location F5H in set 1, bank 1. P4.0–P4.7 can serve as inputs (with or without pullups) and outputs (push pull or open-drain). P4.7–P4.0 can serve as segment pins for LCD or you can configure the alternative functions:
Low-byte pins (P4.0-P4.3): T0OUT, TBOUT, TACLK, TACAP, TAOUT
High-byte pins (P4.4-P4.7): TxD1, RxD1, TxD0, RxD0

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Would this be something I could use to read and write the needed info/data to/from the micro controller chip? Would simply getting a USB to UART cable and hooking it up to those 2 pins work like it would when reading RS232 data on an Arduino?

I have high resolution images of the 995D here so that you can see the main board and all it has to offer for this to potentially happen.

So I am looking forward in learning from others on here as to what I could do for this to happen - or laugh at me and tell me its not possible at which will only get me more interested in doing it:)

Disclaimer: Also posted on these sites:
electronics.stackexchange.com
Electronicspoint.com
electro-tech-online.com
electronics-lab.com
EEVBlog.com

Last Edited: Mon. Apr 12, 2021 - 03:40 PM
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StealthRT wrote:
I could perhaps control it (via USB/ATMEGA) by using my PC and touch screen instead of physically doing so with my hands. Being able to control it via PC would allow me to mount the 995D under my desk and out of sight so that I have more room to work with on the top of my desk.

I'm not sure I'm following what it is you want to control, on my rework station, once I set the temps and air flow, the only control I have touched since the initial setup is the on/off button?

It's not like you need to keep adjusting it for every reflow you do!!

 

Jim

 

 

(Possum Lodge oath) Quando omni flunkus, moritati.

"I thought growing old would take longer"

 

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Lots of micros have a USART, (and hence TxDAta and RxData pins.

 

That doesn't mean that the micro's software was written to use them for anything meaningful.

 

I think you had hoped you could hook up a PC Terminal Program, or your own micro, to remotely control the device via the USART.

That isn't going to work unless the original code, programmed into the device, was designed that way.

 

Also, hooking up a micro to read the LCD, to see what the status of the device is, is certainly doable.

But this isn't a trivial project, and it typically requires a pretty fast micro to read the scanned / multiplexed display and then decipher the data into something meaningful.

 

Another option would be to carefully characterize the performance of the device.

What are the sensors, control signals, and the output levels, (Heat, fan rpm, etc.

 

Then remove the device's own micro and display and add your own.

You re-use the box, power supply, sensors, and the output devices, (soldering iron, hot air, etc.), using your micro and your software.

 

JC

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I'd follow the wires out of that pot that sets the temperature:

 

 

The wiper contacts (yellow wires) are probably connected to the MCU ADC. So maybe a mega, preferably one with a DAC, can replace the pot and trick the device into believing the pot is still there.

Now, why did they use a dual pot I have no idea. I suppose red a black are VDD and GND respectively, but why is each pot connected in a reverse way?

Maybe it increases precision somehow?

 

So one pot will be a potential x and the other at VDD-x. The mega would have to simulate this somehow (using low-pass filtered PWM DACs maybe?)

Last Edited: Mon. Apr 12, 2021 - 11:56 PM