So there are numerous Famicom / NES clones, some of them are portable handheld versions.
Let's see what's inside one of them. This one has a cartridge slot along with "many" built-in games.
It has li-ion battery, usb charge cable and tv out cable included, so you can actually play it on tv. But it lacks of second controller and does not have a select button. In some games you can not select "continue" because you do not have select button :)
Single pcb design. LCD is not 4:3 but image does not look stretched.
This black blob is the main CPU+PPU chip, unknown.
Edge connector for cartridge on the back. USB battery charging circuit. Main crystal. And there is 16Mbit CMOS flash where built-in roms are stored. This pcb can accept flash in different packages. 3 color wires are soldered by me, it's for speaker and battery connector, old wires were rusty with failed soldering job.
This is to compare cartridge size with GameBoy cartridge, very small.
Inside there is the same 16Mbit CMOS flash chip without any fancy mapper chips. It just replaces a built-in flash when inserted.
Ok, so I recently got this heavily used Nintendo 3DS which was not turning on fully. Blue light comes on then it makes popping sound with a little backlight flash and shuts off.
I tore down it into pieces while searching for faults. Found broken touch screen flat flex cable.
Also I found flat flex (ribbon) cable with some traces been broken in the top half of the 3DS and that was the culprit of popping sound and shut off.
This flat flex (ribbon) is connecting top screen backlight, 3D control ? and speakers. Any fail in the backlight circuits of top or bottom screen and 3DS will shut off with popping sound.
So it's easy to fix, just order a replacement cable. No way :)
Checked with multimeter and found there are only 2 traces broken.
I took some hair thin enameled wires. I then scraped off flat flex (ribbon) traces to copper at the connector side and soldered wires there.
Also soldered these wires to connector on lcd side.
And it works :)
I then glued wires to the flat flex cable with tape.
Putting all that flat flex (ribbon) cables back through the hinge was huge pain though.
I'm using my UT61E a lot. One great feature it has is that it can send data to pc for data logging. And it has interface cable included in the box with no additional cost. But the cable is RS232C compatible using DE-9 connector and +/-12V logic levels.
Do you have DE-9 connector on your laptop? I don't :) You obviously can use that RS232 to USD Adapter cables, but DIY guy can make his own cable, right? Add bluetooth too perhaps?
Let's take a closer look at the supplied RS232C cable:
From the first look it has only one working "eye". Which means there is no connection from PC to the meter, easier to hack then.
Definitely only one RX IR sensor diode used, TX circuitry is not populated.
Here is a schematics I reversed from the pcb:
This thing pulls up RX line when IR diode senses light from the meter. UT61E sends inverted serial signal to its IR led.
There is a bit of space inside this sensor box. And I need to fit a circuit inside, which senses IR light and pulls down RX line from 3.3V to Ground. This is classic UART serial interface.
Unsolder everything from the pcb except IR sensor diode.
This is new schematics using 2 n-channel mosfets, any general purporse mosfets will do. I used 2N7000.
R1 needs to be set lower than original because we are using 3.3V now and there is not enough juice to turn Q1 on fast enough with 4.7k.
OK, then I made this piece of art:
This fits perfectly inside original enclosure. New cable needs only 3 wires: +3.3V, GND and RX, I cut the rest. You may be wondering why I call it RX, well this is how DE-9 was wired. RX means PC side RX pin.
At this stage you already can connect UT61E to the microcontroller or Arduino or anything else which understands 3.3V UART. But I started it as USB mod, so we continue.
I have some CP2102 Serial UART TTL USB converters laying around and this is enough for this mod. Just connect that 3 wires and there we go.
Female header used so I can disconnect CP2102 converter and use it anywhere else.
Raw output from the meter:
Correct serial port settings for this meter are: speed 19200, bits 7, stop 1, parity odd.
But, there is more! You can even add a Bluetooth feature to this UT61E multimeter. It's easy as soldering 6 wires to some serial bluetooth module with this mod. UT61E with Bluetooth, sounds great! Interested?
Can you play your Game Boy Micro for several hours? I can't till now.
This blog is all about diy, so let's make a new battery for it.
In my region original battery cost a lot and I searched for similiar size lithium battery.
And found this 9v rechargable lithium battery.
I thought there are 2 3.7v lithium cells in series inside and I was right. You can actually build two batteries for the price.
Protection circuit inside which prevent deep discharge and overcharge.
I cut out protection pcb and split battery cells.
Then I unwrap original battery to compare old and new cell sizes.
Checking how it fits inside Game Boy Micro.
New cell is half mm thicker, but it's a no problem.
Then I soldered wires from original battery and tested charging and playing.
I also added a sticker from original battery, so it looks almost original =)
New cell has a bit more juice too. Works and chrages great, as expected. Battery cover sits ok.
New enhanced version of Gameboy Color quality loud sound mod is ready. It's called GBAmp2s. It's ready to order at tindie.com
Difference with the previous version is that it is using different amplifier ic with more gain. Also it uses stereo audio signal from Gameboy. And you do not need to install additional capacitor to remove loud hiss/hum from the speaker. A bunch of quality capacitors already installed on the GBAmp2s mod pcb.
Bare and assempled pcbs:
And here how it looks installed in the Gameboy Color:
Yes there are couple more wires to get stereo audio to pcb. This new pcb design has all connections marked on silkscreen, so it's easier to install.
New pcbs are made by hqew.net which service I will review later.
Found some unused parts laying in the box, let's make something.
How about battery powered wireless speaker, portable speaker for your phone or player. What wireless technology I going to use? Bluetooth ofcourse.
Let's take cheap speakers like this for example Pyle PLMR24. I bought these to use outside, but...
"Completely Water Proof" with a big hole in the front. I thought it should be sealed. Do you see advertised "Capacitor Crossover Network"? I don't. Just wires. Those "1.75" Wide Dispersion Cone Midrange" and "1" Super Dome Tweeter" made of 2 identical piezoelectric transducers, have a spare.
I'm going to listen mostly talk podcasts on this wireless speaker, so, doesn't matter much.
As a bluetooth A2DP receiver I'm going to use KRC 86A/B V3.2 but any other A2DP bluetooth modue will do. KRC has CSR BlueCore5 bluetooth chip and making a bit of hiss noise when connecting.
Next I need a sound amplifier. I took TPA2005D1 ic known from my GBAmp project. It's only 1.4W power but for my purporse it is enough. And it is class-d very efficient amplifier, good for batteries. I'm going to use 18650 li-on single cell battery.
I measured width of the bluetooth module pcb and designed amplifier pcb to be glued on top of module pcb. Then I made a couple of amplifier pcbs at home with most working method, one for backup.
There are many capacitors with small capacity, I have not any bigger capacity caps in stock.
Then glue it with double sticky tape on top of bluetooth module. And connect wires.
As you can see the final amplifier version configured to 18dB gain.
Add a battery holder, tape and glue it all to the speaker back.
You can see blue led glowing, means it is conneceted. I'm thining to put it all insude and add charger pcb and a swith, that will look much better. But for now, it works s is. Battery will last for several days I guess. I already used it for 10 or so hours.
An encoder used for tuning to frequency. I'm using an encoder with push button which used as search function to auto tune in fm station. Couple of caps used for debounce..
I used old pc speakers, which already has amplifier inside and a transformet to power this fm radio. Just added 3.3v linear regulator in dead bug style.
I had RDA5807P fm radio module from china. RDA5807P is a clone of TEA5767 including i2c commands and functions etc. Read the datasheets for rda5807p and tea5767. Any similiar module will do.
I then wrote a driver for rda5807p and application code to control frequency with encoder etc. As for PLL tunning I had to precalculate a table for fm radio spectrum because my msp430 chips only had 2kb of flash.
Cram it all inside the speaker housing.
And the whole look.
Antenna wire goes out from speaker's "phase inverter" hole.