Weekly Update: June 10, 2017

One step forward, one step back, and maybe a step or two to the side.

No, we’re not dancing. I’m describing the power for the V3. With BronyCon approaching faster than I’d like – 9 weeks away from now – I can’t really take too much time to re-design things. I tried two things: One, a separate power supply board, and Two, using a single buck/boost regulator.

Neither of those are going to happen.

The separate power supply board is simply too expensive to start off with. If I was getting 500 of them, that wouldn’t be an issue, but with a production run of around 100 units, it’s about 3x more expensive than it should be. That said, an updated V3, when I have the opportunities to purchase in larger quantities, may feature a separate power supply board. Additionally, such a power supply board would be available separately for whatever sort of crazy contraptions you can think up. I AM going to be integrating most of the power supply board’s design into the V3 – That is, the ATTiny84 for control and additional GPIO and battery monitoring.

The voltage regulators, on the other hand, are going back to the ones that have been tested and I know work. The single buck/boost one I simply could not get functioning. If that was an issue with the soldering, or board design, or something else, I don’t know – And I don’t really have the time to figure that out. Both of the other regulators I have tested and work fine. Thankfully, there isn’t much of a price difference, it’s just a matter of squeezing them onto the board. Which I’ve already done.

In other news, it seems unlikely that there will be a case ready for BronyCon. While I really hope this next design will be the one I get a fully functioning prototype out of, I’ve said that for the other ones, too. I’ll be honest – There is entirely a possibility that the V3 will not be ready before BronyCon. I really doubt that will happen – Especially with having someone else manufacture them – but it IS possible that things just don’t work out. That said, there’s still about six weeks to work with, so I’m not terribly worried yet. I’ve already placed an order for more prototypes, so right now I’m just waiting for them.

At this point, I’m sure you know the drill. DiscordTwitterFacebook.

Weekly Update: June 3, 2017

Hey guys!

I’m late again. Was working on the latest V3 prototype last night and suddenly it was 3 in the morning. Oops. At least I grabbed a shiny picture:

So, what makes this different from the previous versions? Well, pretty much everything. It’s largely the same circuitry, but everything’s been moved around and reorganized to fit better and have fewer traces having to go entirely across the PCB just to go back to where they started. There are a few changes, though.

First and foremost, I’ve decided to try and make a separate “PowerBoard” for the device. This consists of a boost-buck regulator instead of two separate regulators, plus an ATTiny84 to control it. The ATTiny84 has 11 GPIO pins, of which two are being used for I2C communication with the ESP8266, one is being used for monitoring battery voltage, and the last one is being used to control the voltage regulator. This leaves seven GPIO pins free to use for the device the PowerBoard is attached to. The V3 ties one of them to a button, to turn the power back on when that button is pressed. The ATTiny84 runs directly off of the battery power – or USB power if it’s available – so is, essentially, always on and monitoring the inputs. Its power consumption is fairly minimal, and will be minimized as much as possible. It’ll likely be put into a sleep state when the regulator is off, turning it back on when it’s awoken.

The PowerBoard being an I2C device does a few good things for the V3 board. First, as it monitors the battery voltage, the I2C ADC can be removed. That ADC was, roughly about the price of the ATTiny84. The single voltage regulator instead of two is also about even in terms of price. Additionally, since the PowerBoard is an I2C device and we’re not controlling the voltage regulator directly from the ESP8266, we’ve freed up a GPIO pin on the ESP. That has now been tied in to a transistor which controls the backlight, removing the need for the I2C Digital Potentiometer.

In addition to that, there’s the six unused GPIO pins from the ATTiny84 that are broken out, in addition to an ICSP header for programming said ATTiny84. In all, the 18-pin breakout header has pins for all three voltages: +5v USB power, +3.3V Regulated power, and the Battery raw voltage. The regulator can handle anything from 1.8 to 5.5v, making a LiPo battery perfectly suitable (Although I’d recommend adjusting the ATTiny84’s programming to not discharge it too much. And there’s no charging circuit). There’s also two ground pins, the ESP’s three SPI pins, the two I2C lines, the ESP’s ADC line (Which is linked to the buttons, but with the right resistors you can add more. Or you can read them from something else), and all seven of the PowerBoard’s GPIO pins. One of them is linked to the power button, but this can allow for an external wakeup from another device.

The PowerBoard also allows for a great deal of versatility in V3 design. If I wanted to make a LiPo powered V3, it would only require changing the battery and a different PowerBoard with a charging circuit included. If I decided to redesign with a more robust and powerful regulator, it would only require changing the PowerBoard.

I’ve ordered some prototype PCBs for the PowerBoard, which will let me test the voltage regulator circuit independent of the V3, and I’ve inquired into what would be necessary for manufacturing it. It may turn out to be too expensive to do in this fashion, but at the very least I’ll have the circuit tested and not have to worry about that on the V3.

Until next week, you can find me on Discord, on Twitter, and/or Facebook.

Never Finished Means Always Improving

When I set about to design the Verison 2 of the DigiBadge, I had no expectations that this would be the final end-of-the-line product. I expected to learn a lot, to experiment a lot, and to be able to do a lot more. So far, I have exceeded my expectations.

With that in mind, I’m going to go ahead and ‘Announce’ the Version 3 badge. It won’t be as radical a change as the V1 was from the V2, but there will be significant changes. I’ve talked before about adding the SPI Flash card to it, for some persistent data storage. This was initially going to be part of a Version 2+, but things have changed enough to warrant it being called the Version 3.

In addition to the flash memory storage, there will also be a more pins freed up, starting with a change to the control stick input. Initially, I had the control stick running through a bunch of resistors to a single analog input, with each direction being a different resistance. I couldn’t get that working and ended up using five direct inputs instead. The Version 3 will revisit this single analog input, freeing up four other pins. Another pin will be freed by tieing the screen’s Reset pin to the board’s Reset, but then that pin will be immediately taken by the SPI Flash’s CS line. I’ll be trying to break out these pins in the board, but space is limited, so I may not be able to do so.

Speaking of space, though, this leads me to the most significant change. The Version 2 uses two AAA batteries. Why? Well, because 3v is a perfectly acceptable voltage to run pretty much everything at. And it provides decent enough battery life, too. But two AAA batteries are large. Huge, even. They take up about 2/3 of the back of the PCB. I did some thinking, did some checking, and it’s easily affordable to change this.

In series, two batteries provide double the voltage at the same capacity. Two AAA batteries have roughly 1200 mAh of capacity… but so does one, just at 1.5v instead. So, I thought – Maybe I could include a boost regulator. After a bit of searching, it turns out that yes, I can, without much additional expense either. This will do two significant things. One, it’ll provide a nice, solid power state for the board at all times until it dies. This means no more screen dimming. No more worrying about the SD card going below its proper voltage threshold. Two, it’ll allow a lot more of the battery to be used. Currently, the Version 2 badge drops below useful power at about 2.7 volts, or 1.35 volts per cell. Realistically speaking, there’s a TON of power left in the battery – Maybe somewhere between 3-4x as much. The voltage regulator I’m currently looking at goes down to 0.8 volts. While it will use more power, I don’t expect to see much of a difference in expected lifespan.

The Version 3 will fit into the same case as the Version 2, which is why I mentioned those size restraints above. However, I AM working on something for the more adventurous among you: The return of the ‘Hacker’ Badge.

The Hacker Badge will be a significant change from the Version 3’s normal layout. It’ll be larger. A bit larger. It’ll feature the same components, but in a different manner. First, the nav stick will be moved to the front. Second, every pin that can be broken out will. There will be the FTDI connector, along with an ISCP header and headers for the digital pins and analog pins that are free, aproxamately 4-5 of each. It’ll have a different power switch, which will make Alabaster a lot happier in designing a case for it.

There are also a few other devices I’ve been working on, most notably the Super badge which I’ve covered before. I’ve also designed a breakout board for the SPI flash which I’m using, and an I2C controller for a MUX chip, mostly just because I can.

I’ll keep you guys updated with how things go!

-Andon