Time has come to spruce up my YouTube channel and start putting more content out with a bit more substance.
I’ve been busy with getting settled into university and now feel I have time to put more effort into my channel.
Sundays I will be releasing new teardown videos, these may be single part teardowns or multi-part, depending on how complex and how long it runs.
Fridays will be my cool down days from university so I will be recording some gaming videos (possibly live stream, not sure yet) and I will have it edited and released the following Friday.
Another change I have made is that I have now signed up with Patreon, I’m still learning how to set this up so my page on there needs a bit of work. My intention is to have it in place if people are interesting in supporting my work.
Benefits of being a Patreon will be as follows:
Early access to my videos
Credits on Patreon supported videos
Patreon only content when it is available
More benefits to be established as time goes on…
If you are interested in supporting my channel, please go to my Patreon page.
Ok, so the Hipstreet Phoenix tablet that I repaired the power button on a few months back got knelt on. The screen didn’t like it very much and refuses to work now due to a crack.
Looking at the bottom edge of the tablet you notice there is a nice selection of features.
From left to right: Headphone/Headset (Covered by my thumb), Mic, Micro USB, Mini HDMI, A 5V charging port, reset button, microSD card socket.
I decided to order some items in to see if I could use these ports instead of relying on the LCD/touchscreen interface.
Here is the board in all it’s glory. a fraction of the size of the case it is in.
Firstly I have already ordered in some USB OTG cables. (Actually ordered a set 4 months ago on ebay and not seen any, and ordered a set 2 months ago and still waiting for both). They haven’t arrived so I did a quick bodge to use USB OTG without the proper cable as you will see in the picture below. I’ll detail that soon.
Next I got a HDMI cable, turns out I purchased a MicroHDMI cable 😛 but I went out today and got the MiniHDMI cable and plugged it into the tablet and switched it on. Nothing appeared on the screen until it was a good minute into the booting but it worked ok, it was a little too large for my screen but I have an old TV so I found that with a lot of things, but the main point is that it works on HDMI!
I found that I could use the tablet by pressing on the touchscreen but it’s somewhat hard to know where your touching when the LCD is broken and your watching it on a TV.
Next I turn my attention to the USB OTG situation. I heard that you can plug in a mouse and/or a keyboard and use them with Android based devices, I have never seen this before myself so I was curious. The only spare keyboard I have is an old PS/2 Style keyboard so I plugged in my PS/2 to USB adaptor, the keyboard initialised (as noticed by the lights coming on for a second) but I did notice the display flickered while doing so but it didn’t seem to do any kind of input. Maybe it was drawing too much current and was disconnected by the tablet after initialising, I will find a USB keyboard and try again later.
Next I try a USB mouse, the only one I have at hand is a cheapo wireless once from Dollarama, this appeared to work fine, I tested it and had a quick game of solitaire to test it.
Ok, so the bodge that I did to get USB OTG up and running is based on instructions I found here:
What I did was locate pin 4 on the microUSB socket on the PCB and trace it to a point where I could solder on a wire, luckily I found a test point and used that, I also attached a 2nd wire to GND and brought them both out (The orange and white wires). In order to use USB OTG I just short them together. Now I needed a microUSB to Female USB-A connection, I simply took an old dual USB socket and bridged the 2 connections together at it’s cable header, turning it effectively into a crude gender changer for USB-A then used a normal microUSB-USB-A cable to connect it to the table. voila!
This is only a temporary solution until my proper cable arrives.
This is the current state of the device.
Plans for the future:
Put the PCB in a small plastic box make new buttons on the front
use external power into the 5V charger port
Use a small USB hub (preferably powered) with a proper USB OTG cable to allow keyboard, mouse, and other USB devices
Modify the Android OS on the device to allow me to use it for something useful
That’s all for now, hopefully more to come soon.
I made a proper USB OTG cable (Using the website mentioned above) and found a USB keyboard, this worked great 🙂 I then found a small USB hub, this one is a 4-port USB 1.1 hub unfortunately but it’s good enough for mouse and keyboard use, which it did 🙂
I also found a 5V charger with the same connector as the one found on the bottom of the tablet and it is now currently charging.
I unplugged the LCD and Digitiser cables and it still takes a while until it enables the HDMI, I did a factory reset too and it had nothing on the HDMI for quite a while, I was a little worried that it was showing something on the LCD asking me to confirm something during startup. This worries me about re-flashing the firmware as I’ve seen some devices require you to do some selections on the bootloader, I have to rebuild the volume button set in order to test this but I will have to see if it will initialise the HDMI.
Someone commented on my youtube video about the EPROM as combinational logic stating that the video was too quiet. Unfortunately my original footage is no longer available to re-upload so I decided to redo it. This time I decided to expand upon the concept by including other ROM types than just the EPROM since the concept does apply to all parallel ROM’s.
The software I designed should work the same for different types of ROM’s since they follow the same concept.
A few years back I came across something in an old Z80 book that mentioned that EPROMs can be used a crude logic devices, though only supporting combinational logic, you could craft the data to mimic logic. Recently I tried it out and found it to work really well.
I recently uploaded a YouTube video showing my experiment.
In the video I hand-crafted the code to go into the EPROM, this took a while just to act as 2 logic gates, so I decided to have a go at writing a bit of software to do it for me.
I wrote this in Delphi and you can put up to 8 boolean algebraic expressions into the boxes, one for each data line output. You select how many address lines you are using (you can put only the number your actually using and ground the rest in hardware) Then you hit the “Parse” button and it will go through each address combination using the boolean expression to create the required data for each location.
This is only a first version so may have some kinks that need to be ironed out. The handling of parenthesis is very crude and does not take them into consideration with order of operation. it does somewhat process the order as ~(NOT), * (AND), +(OR), ^(XOR).
Valid inputs are A-P (not case sensitive), these are representative of A0-A15 inputs. Unused Data lines can be unchecked to not have them used
Once you have parsed what you need, you can view the data to the right on the table. Note: These numbers are all in Decimal!
You can then hit the “Save…” button and select where you want to save the binary file. Note: you need to add you own .bin extension, I’ve not added it yet.
Hopefully this will be of some use to people, it’s certainly an interesting concept.
It’s been a while since I’ve posted to my blog, but here is a video I just uploaded showing how I reverse engineer digital circuits.
I’ve been doing this sort of thing for as long as I can remember and I find it very relaxing at times. Nothing better than throwing some nice music on and doing a bit of reverse engineering.
I was recently given a dot matrix LED display by a friend and decided to reverse engineer it so we both can run them, he still has one of his own.
There is a damaged chip on the board which meant that some of the displays didn’t display their 2 bottom rows but I will be tackling this issue in a later video. I will also be transferring the control to a PIC instead of the Arduino as it was not fast enough to get a good refresh rate, and this is without any external communication facilities being addressed.
I found myself some PSU’s at a flee market a few weeks back and decided to pull out the matching pair of 75V PSU’s for some inspection. Much to my delight, they both appear to work fine.
The only issues with them is the neon power indicators are not working (or barely working), and the voltage/current multiply switches for the analogue movements are crusty. And not to mention a non-standard power connector on the rear. These will all be replaced and updated in future videos.
I have decided to replace the analogue meters with LED modules (just waiting for them to be shipped from China on the slow boat) then I will hook them into to sense the output terminals and find a way to recess it in places of the old meters.
For the power indicator, I will find a voltage rail inside the PSU (most likely an opamp rail) and fit an LED in place of the neon lamp.
Please keep tuned for more!
You can subscribe to my YouTube channel to get updates on my progress too.
It’s been a while since I’ve released a video for this series, but I have been doing final tests for the term at college and was a little overwhelmed. But I did my last test yesterday and decided it was time to do an update.
As promised in the video, here is a flowchart showing how the software currently works. This is the basic idea of what goes on.
Do note that the Volts and Current pots on the front of the case do not directly set the current and voltage limits, rather they are read by the Arduino via the ADC and scaled and then that is outputted via the DAC to the actually regulation circuitry. This leaves the possibility of having the push-buttons setting the Voltage and Current instead.
Here is the Arduino code used in this episode, I will be cleaning it up for the final version:
// disable all devices to start with
// set up the LCD's number of columns and rows:
// Print a message to the LCD.
void set_dac(byte chan, unsigned int value,byte ga, byte shdn)
// ga : 0=2x (0-4096v), 1=1x (0-2.048v)
// shdn : 0 = shutdown DAC channel, 1 = output available
// [ A'/B , x , GA', SHDN', D11, D10, D9, D8 ]
conf=(chan&0x01)<<7; // mask out channel number and shift it to bit 7
conf=conf|(ga&0x01)<<5; // mask out gain select and shift it to bit 5 and or it to conf
conf=conf|(shdn&0x01)<<4; // mask out shutdown select and shift it to bit 4 and or it to conf
conf=conf|(value>>8); // or in the top nibble of value left in conf
b = value; // bottom byte of value
SPI.beginTransaction(SPISettings(15000000, MSBFIRST, SPI_MODE0));
digitalWrite (DAC_CS, LOW); // enable DAC
SPI.transfer(conf); // send configuration and top nibble of value
SPI.transfer(b); // send bottom byte
digitalWrite (DAC_CS, HIGH); // disable DAC
unsigned int get_adc(byte chan)
unsigned int a,b,c,conf;
conf=conf=((chan&0b00000111)<<1)|0b00110000; // create configuration byte
SPI.beginTransaction(SPISettings(8000000, MSBFIRST, SPI_MODE0));
digitalWrite (ADC_CS, LOW); // enable ADC
SPI.transfer(conf); // send configuration byte
b = SPI.transfer(0x00); // receive sign bit & top 4 bits
c = SPI.transfer(0x00); // receive lower 8 bits
digitalWrite (ADC_CS, HIGH); // disable ADC
b = b&0b00011111; // filter out unwanted stuff from high byte
a = (b*0x100)+c; // convert 2 8-bit numbers into a single 16-bit number
unsigned int get_adc_avg(byte chan)
long tempx = 0;
byte ax = 0;