ATTiny1616 - Maker and IOT Ideas

ATTiny1616 Can Bus Controller PCB

Introduction

Over the last few months, we have been working on several prototypes, and some of our regular visitors may recognise some parts of this PCB. But let us begin by telling you what this is about.

As many of you may know, we have already designed several Can-Bus-related development boards, including one based on the ATTiny1616… So why the repeat then? Well, in some of my previous projects, I hinted at combining a buck converter, boost converter, lipo cell charger and Ideal Diode circuit into one PCB. I did at that time not tell you why.

To make a long story short, this project will eventually be used in my car, to provide more modern cabin lighting, which is quite a bit more than the standard on-or-off and on-when-open-the-door, off-when-close-the-door type of thing…

I own an old Honda City that I use mainly for a run-around to and from the farm, as well as seeing clients… Roads are bad, and this older car (actually quite old – 22 years) is the most cost-effective, in terms of being able to repair by myself, and not be worried about it if it gets a bit abused.

Unfortunately, the technology in the car is dated… a single yellowish cabin light right in the centre of the cabin – and not bright at all. Having to use the car at night, and then frequently scratching around in equipment bags when arriving at a client, becomes a pain with bad light… So I have decided to give it a bit of an upgrade and add CAN-bus-controlled NEO-Pixels to the cabin. For now, let’s say three sets, left, right and centre of the cabin. I also prefer a red light at night over white, especially if I have to drive again soon afterwards – a simple remnant from my days in the military, where it became quite clear how white light can temporarily damage your night vision.

NeoPixels can also be dimmed/brightened and seem relatively inexpensive.

Let us take a closer look at exactly what I want to do…

Powering the module

For the sake of clarity, this particular module will be installed front and centre in the cabin, just behind the rearview mirror. It will control two sets of 8 neopixels ( or up to 12 per module ) on two separate PCBs, which will cover the driver and front passenger area of the cabin.

The module will be powered by the vehicle’s 12v battery, as well as from a single 18650 Lipo cell. This means that we would need some clever tricks, in the form of a buck converter to step down the 12v to 5v, a way to monitor and recharge the lipo cell, a boost converter to boost the lipo cell voltage back up to 5v as well as a voltage “OR-ing circuit” to prevent reverse charging the lipo cell etc…

In its current state, the PCB is to be considered a test rig, since I have quite a few unknown variables that need to be thoroughly tested before actually installing this thing into a vehicle.

These are :
1) I would like to know if the ideal diode chip that I used functions well when used in a parallel setup, The reason for that is, that a single chip is capable of just about 1A of current… thus, in my reasoning, placing 3 in parallel would give me the 3A capability that I require – Let’s see if it does…
I could also not get hold of a suitable 3A capable ideal diode chip that was cost-effective, or did not have some strange MOQ or other logistics issues ( Yeah, seems like getting some stuff in SE Asia is difficult unless you are willing to pay unnecessary “special” charges and import duties etc … Element14 ( not sponsored) seems to have a limited selection of ideal diode solutions, but their pricing is good, and there are minimum hassles with shipping etc… I don’t bother with the other two big suppliers, D…. and M…. as they have too much red tape for a hobbyist to navigate to make it cost-effective to shop from them.))

2) Providing that the ideal diode solution does work as expected ( on the PCB) – having tested it on a breadboard seems to be working fine, there is the issue of monitoring the lipo cell, getting it charged, controlling the boost converter to provide power when needed etc…

All of this means that all the separate circuit modules on the PCB can be enabled or disabled by jumpers, and later, if all works as expected, maybe by another controller PCB… Who knows?

Getting back to power the PCB, I have used my standard buck converter circuit, based around the MP9943. This circuit seems to be very reliable, provides enough current, and is cost-effective.

I have also provided an auxiliary voltage output ( 5v) and some telemetry and control capability to the buck converter circuit, in the form of an enable-disable jumper, and the PG signal from the chip, to maybe be interfaced with a microcontroller later.

Charging the Lipo Cell

Once again, I made use of an existing circuit, with which I have had a lot of success in the past. This circuit, based on the MCP73832 from Microchip ( not sponsored) served me quite well in previous projects, and is once again, cost-effective and easy to implement. One negative is that they do seem to be a bit finicky, and not extremely robust – but when they work, they excel at it…

Once again, I decided to provide control logic to enable or disable this part of the circuit completely if needed.

Supply “OR-ing” circuit

This is the most experimental part of this entire circuit board, since, as mentioned above, the MAX40200 is rated at 1A maximum current. It is tiny and cheap, and also readily available… I am hoping that by using them in parallel I can achieve my goal of allowing the full 3A of current to flow from the buck converter, without releasing any “magic smoke” or other issues…

While, at the time of writing, I have not yet received the PCB, I am positive that all may just be fine, it remains to be seen how this will turn out during actual testing of the board.

Note that I have used a total of 6 of these, U8 to U11, with 3 per “voltage/current supply” channel. J3 and J4 are used to enable or disable the two supplies, with J3 being the buck converter input, in turn, powered from the vehicle 12v supply, and J4 begin the output from the boost converter, powered by the Lipo cell.

Boost converter circuit and MCU power

The boost converter is based on the MP3423, also from Microchip ( not sponsored). This circuit also performed very well in my initial test projects, with the only issue being it extremely tiny footprint, which really makes it quite difficult to use in a hobby environment, even with hot air and reflow equipment available… It is however also quite cheap, and readily available…

J5 provides enable-disable control to this part of the circuit.

With this relatively complicated power supply circuit, I thought it necessary to be able to completely isolate the ATTiny1616 and other integrated circuits from any power until I am completely sure everything works as planned…

J6A and J6B thus form a complete electrical isolation “breaker” that will prevent any voltage being provided to the microcontroller and other components on the PCB. I have doubled up on these jumpers, to allow for sufficient current flow, since I plan to use quite a few NeoPixels on this PCB… With up to 60mA of current required per pixel, that quickly adds up…

Voltage monitoring

Provision was made to monitor the output voltages of the Lipo Cell, and buck and boost converters by using the analog inputs on the ATTiny1616. These can be selected by setting the jumpers on J9, J10 and J11

Alternatively, the analog inputs can be used for other applications be leaving the jumpers off, in which case these GPIO’s will be available on H6 as PA4, PA5 and PA7

The ATTiny1616 microcontroller and UPDI programming port

The heart of this PCB is the ATTiny1616 microcontroller, (microchip, not sponsored)

I decided to use the chip once again due to its low cost, as well as the fact that I do not need a very powerful processor for this application. The only issue is that requires UPDI programming. In my case, I have had no issue with that yet, but other readers did mention that they had issues with them…

The UPDI header is at H1. This header can also be used to power the processor and other integrated circuits on the PCB independently from the Power supply, like in the case where J6A and J6B are left unconnected. This use case will provide me with more testing opportunities to test the board without possible variables from the power supply circuit(s).

Peripherals like I2C and the UART were broken out onto headers H3 for I2C, H4 for UART. These can also be used as GPIO pins ( remember to disable the I2C pullup in J1)

CAN-Bus Support

CAN-Bus support is provided by the MCP2515 (U2) and TJA1050 (U3) chips.

With access to the MCP2515 GPIO pins on H5. J2 is a 120ohm termination resistor, usually enabled at the start and end of the bus to prevent reflections.

CAN-0 is connected to the bus.
An additional 12v input/output header is provided at H7

NeoPixel Header H2

The NeoPixel strips are connected to H2. They are controlled from GPIO PA6 on the ATTiny1616. I have designed around a total of 24 of these at a maximum, with a total current requirement of 1.4A ( 24 x 60mA max per pixel / 1000 = 1.44 A) .

One important fact to know about NeoPixels is that the consume about 1mA per pixel even when in the OFF state. This is due to the internal control chip requiring power to operate. While 1mA bay be a very small amount of current, a lot of them does however quickly add up, and can thus potentially drain a battery completely over time…

To prevent this from happening, I have included a PMOS switch on the VCC pin at H2. This means that no power will be fed to the Neopixel strips unless you specifically pull GPIO PC1 low.

Manufacturing the PCB

I choose PCBWay for my PCB manufacturing. Why? What makes them different from the rest?

PCBWay‘s business goal is to be the most professional PCB manufacturer for prototyping and low-volume production work in the world. With more than a decade in the business, they are committed to meeting the needs of their customers from different industries in terms of quality, delivery, cost-effectiveness and any other demanding requests. As one of the most experienced PCB manufacturers and SMT Assemblers in China, they pride themselves to be our (the Makers) best business partners, as well as good friends in every aspect of our PCB manufacturing needs. They strive to make our R&D work easy and hassle-free.

How do they do that?

PCBWay is NOT a broker. That means that they do all manufacturing and assembly themselves, cutting out all the middlemen, and saving us money.

PCBWay’s online quoting system gives a very detailed and accurate picture of all costs upfront, including components and assembly costs. This saves a lot of time and hassle.

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to who will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly and Testing

This project has a lot of specific details regarding testing and assembly.
Therefore I have decided to put all of that in a separate post, that you can access
here.

CAN Bus support with the ATTiny1616

ATTiny1616 QFN with Can bus support on a breadboard

A short while ago, I started looking at alternatives to the ATMEGA328P ( the chip used in the standard Arduino Uno). That experiment turned out quite well,
with two of the three chips turning out to be useful, the ATTiny1616 and the Atmega 4808 – The ATTiny 202, while working great, has quite a few severe limitations, due to the size of its memory, as well as library support, limiting its actual useful use quite a bit for my purposes.

In this post, which is part of a two-part series, I will look at adding dedicated CAN Bus support to the 1616 and 8408. I am planning to add some gadgets to my car, and would like to have it controlled by a CAN bus interface, and just maybe, interfacing with the CAN bus on the car as well – at least in the future…

This experiment will thus consist of two prototypes with onboard CAN hardware, to be initially used on the bench while building and testing my gadgets – more on them later, if and when they work out the way that I imagine.

What is on the PCB

The ATTiny1616 microcontroller, in a QFN package, has been married to a MCP2515 and a TJA1050. These chips, while old, are still easy to get hold of,
and I have quite a few of them lying around from previous projects. It did thus seem to be a good starting point. The fact that their libraries also works perfectly with the ATTiny1616 and Atmega4808 also went a long way towards selecting them for the project.

The PCB is similar to the ATTiny1616 QFN breakout that I have designed before but with the addition of the CAN-related components.

ATTiny1616 QFN development board with CAN bus, after reflow soldering

Schematic and PCB Design

The schematic is a variation on the earlier breakout PBC, with the addition of the CAN-related components.

Can bus related components - for use thie the ATTiny1616 MCU

The PCB design has also not changed a lot, I have just added the CAN components to the right hand side of the PCB, and adjusted the routing.

PCB layout design for the ATMEGA1616 with CAN bus Development PCB

3D render of the PCB, with the header pins in non-breadboard configuration – with the CAN bus connector not fitted.

Manufacturing

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

I usually can not wait to receive my creations back from the factory – I mean, how can somebody not get excited about receiving their own PCBs back from the factory, especially if you know they will be of the high quality that I have come to trust with all of my PCBWay orders?

This is especially true of the smaller PCBs, as well as those with smaller-sized QFN components, with this board definitely not being an exception.

ATTiny1616 QFN Dev board with Can Bus, in packaging - straight from the factory — PCBs in factory packaging

PCBs in protective wrapping, after opening — PCBs in protective wrapping, just after opening the package

This PCB once again requires the use of a stencil, to accurately apply just the right amount of solder paste to the pads, especially the small QFN package pads of the ATTiny 1616…

High quality stainless steel, laser cut stencil. High accuracy. Definitely worth the investment — High-quality stainless steel, laser cut stencil.

Stencils, at least from my point of view, can be a controversial subject, with some hobbyists arguing that they are not worth the additional expense… I do however believe that they actually save you a lot, in time that you don’t waste on reworking a PCB due to solder bridges, in the correct amount of solder paste that is applied, in the correct thickness, and also time not wasted on the cleanup of the mess that can result from manually applying solder paste.

After solder paste application, all the components are placed in their correct positions, ready to be reflow soldered. — PCB ready for reflow soldering, after manually placing the components in their respective places

The PCB is now reflow soldered with a hot plate, and allowed to slowly cool down afterwards, to reduce thermal shock damage to the joints, that may result from a too-quick cooldown cycle. While I do not own a dedicated reflow oven, the hotplate that I use, seems to match the reflow profile ramp-up of my solder paste, and most of the components perfectly. After achieving a complete solder melt, at about 223 degrees C, I usually switch of the hot plate, and carefully move the PCB towards the edge of the unit, that area is usually a bit cooler than the centre. leaving it there for about 5 to 8 minutes, allow the solder to slowly solidify, after which I remove it and place it on a silicone mat to cool completely.

Through-hole component soldering, and testing

The next step is soldering all the through-hole components, usually header pins and connectors into their respective places. The board is then placed onto a solderless breadboard, and various test sketches are uploaded via a homemade UPDI programmer.

These include the infamous blink sketch, to make sure the chip is alive and survived the reflow soldering. That is followed by a CAN loopback test, and then the actual CAN firmware… I make use of the excellent MCP Can library from Garry J Fowler, as well as the megaTinyCore Arduino core, from Spence Konde.

My thanks to both of these gentlemen, for their excellent and easy-to-use software. A special shoutout to Garry J Fowler, since his MCP Can library correctly releases the CE pin of the device when not in use, thus not locking up the spi bus. [ This is something that many other libraries do not bother to care about ] …

Conclusion

This was once again a fun project to design and assemble. The real testing and development can now start at full speed, as this is just meant to be a tool, with a further revision later down the line. It does of course help a whole lot that I can completely trust my PCB manufacturer, PCBWay, to deliver my PCBs to me EXACTLY as I designed them, and at extremely high quality and precision! Thank you for that!

A complete ATTiny1616 Dev Solution

A few weeks ago, I started looking into alternative development solutions to reduce the effect of hard-to-get or more expensive-than-usual ATMEGA328 chips. One of the chips that I found to have potential was the ATTiny1616.

There seemed to be quite a lot of stock, and the prices were reasonable. Some additional hardware, like a dedicated UPDI programmer, had to be designed or bought, as the ATTiny1616 required UPDI to upload and flash code.

Setup to program ATTiny1616 Breakout Module – Power Module ( Left – Optional) ATTiny1616 Breakout – Center, UPDI programmer ( Right)

While the breakout worked flawlessly, I found the programming setup awkward and cumbersome. That was the cue to take the next step and create something that was easier to work with.

Old versus new. ATTiny1616 breakout module and programmer (Top) versus the all-new ATTiny1616 Development board, with all required hardware, included.

The new PCB offers a development cycle that is very similar to a standard Arduino UNO or Nano. Plug it into a USB port, write code, upload and repeat…

What is on the PCB?

Starting at the Top Lefthand corner, we have a USB port, with a CH340N Chip. Note that this IS NOT A SERIAL UART. This is an integrated UPDI programmer, that can also be used in stand-alone mode to program external devices. (by moving J3 to the left, and using the UPDI header).

Below that is the power supply section, featuring two LDO Voltage regulators, providing 3.3v and 5v DC to the system. A DC barrel jack is included, to supply between 7v and 12v external DC voltage to the system. ( NOT to be used together with a USB cable)

Jumper J2 (next to the DC barrel jack) is used to switch the entire board logic level between 3.3v and 5v DC. A power indicator LED, as well as a standard user LED ( on pin D16), is also included. The rest of the PCB is dedicated to the ATTiny 1616 -SF, this time in a TSOP form factor. ( The original breakout used a QFN, but I realised that that may push away a lot of potential users, as QFN packages are quite difficult to solder without the proper equipment. A TSOP package is more accessible to everyone)

A total of 17 GPIO ports are available, of which each is labelled with an Arduino compatible label (D0 – D15), PWM ~ capable pins, and alternate functions like UART, SPI and I2C. Please Note that the onboard USB port IS NOT A UART

Features on the PCB – Summary

Reset Circuit with Push button – The ATTiny1616 shares its Reset pin with the UPDI programming pin. This will cause problems, requiring an HV UPDI programmer to fix. To resolve this issue, a reset circuit, comprising of a p-channel logic level Mosfet, that is wired to be constantly on, is connected via a suitable resistor on its gate, to a push-button to ground. pressing the button pulls the gate to ground, switching off the Mosfet, and thus the supply voltage to the chip, which equates to a power cycle reset. It is worth noting that the UPDI programming sequence also auto-resets the chip after every upload.
DC barrel jack for powering the device from an external source – 7v to 12DC
Onboard I2C pull-up resistors, selectable with a jumper ( J1)
Onboard UPDI programmer, which can also be used in stand-alone mode.
Selectable voltage logic level between 3.3v and 5.0v ( J2)

Manufacturing

PCBWay gives you one-on-one customer support, that answers you in 5 minutes ( from the Website chat ), or by email within a few hours ( from your personal account manager). Issues are really resolved very quickly, not that there are many anyway, but, as we are all human, it is nice to know that when a gremlin rears its head, you have someone to talk to that will do his/her best to resolve your issue as soon as possible.

Find out more here

Assembly

While this board can definitely be assembled completely by hand soldering, I chose to make use of a stencil, from PCBWay. This helps me by ensuring that the solder paste is applied in exactly the correct amount and place. Hot air or reflow soldering afterwards is a quick easy task. I prefer to use a hot plate to reflow the board, especially since it has a tiny USB connector, which can be quite a pain to solder with hot air, I won’t even go there with a normal soldering iron, as it is beyond what my eyes can handle at this stage.