MicroPython learns a new trick – ISP for AVRs

One of the reasons why the Arduino became so popular was the ability to program it with ease. It meant the end of big parallel programmers that would cost an arm and a leg. The latest installment of CircuitPython from [Lady Ada] and the team over at Adafruit is a library for programming AVR microcontrollers without a dedicated PC.

For the uninitiated, in-system programming or ISP for AVR controllers employ the SPI bus to write the compiled binary to the flash memory of the controller. The discount on the number of pins used itself is a benefit though getting the timings right was a bit tricky in the good old days. Most dedicated ISPs handle this nicely, though they are normally slaves to a host PC where an ‘upload’ button initiates the process.

With CircuitPython (a derivative of MicroPython), programming microcontrollers does not require going through the code-compile-flash cycle. It can be run on a number of processors, however, AVRs are not among them so this neat little library offers the next best thing. Wire-up an Atmega328P or ATmega2560 to a board like the ESP8266 that does run CircuitPython, and you can write firmware on the fly.

There is a complete tutorial on the subject thanks to [Phillip Torrone] and [Lady Ada] which includes some demo files for testing out the functionality. This opens up a lot of possibilities where OTA firmware updates for an AVR co-processor. We expect to see some keychain AVR programmers in the near future taking a hint from the ESP8266 based Two-Factor Authentication featured previously.

Becoming Your Own ISP, Just for Fun

When moving into a new house, it’s important to arrange for the connection of basic utilities. Electricity, water, and gas are simple enough, and then it’s generally fairly easy to set up a connection to an ISP for your internet connection. A router plugs into a phone line, or maybe a fiber connection and lovely packets start flowing out of the wall. But if you’re connected to the internet through an ISP, how is the ISP connected? [Kenneth] answers this in the form of an amusing tale.

It was during the purchase of data centre rack space that [Kenneth]’s challenge was laid down by a friend. Rather then simply rely on the connection provided by the data centre, they would instead rely on forging their own connection to the ‘net, essentially becoming their own Internet Service Provider.

This is known as creating an Autonomous System. To do this involves several challenges, the first of which is understanding just how things work at this level of networking. [Kenneth] explains the vagaries of the Border Gateway Protocol, and why its neccessary to secure your own address space. There’s also an amusing discussion on the routing hardware required for such a feat and why [Kenneth]’s setup may fall over within the next two years or so.

It’s not for the faint hearted, and takes a fair bit of paperwork, but [Kenneth] has provided an excellent guide to the process if you really, really just need to own your own corner of the internet. That said, there are other networking tricks to cut your teeth on if you’d like a simpler challenge, like tunneling IP over ICMP.


Interfacing a Retro Controller using the USBASP

An ISP dongle is a very common piece of equipment on a maker’s bench. However, its potential as a hackable device is generally overlooked. The USBASP has an ATmeg8L at its heart and [Robson] decided that this humble USB device could be used as an interface between his PC and a SNES Joypad.

A SNES controller required three pins to communicate with a host: clock, data and latch. In his hack, [Robson]  connects the controller to the ISP interface using a small DIY adaptor and programs the AVR using the V-USB library. V-USB is a software USB library for small microcontrollers and comes in pretty handy in this instance.

[Robson] does a pretty good job of documenting the entire process of creating the interface which includes the USB HID code as well as the SNES joypad serial protocol. His hack works on both Windows and Linux alike and the code is available on GitHub for download.

Simple implementation like this project are a great starting point for anyone looking to dip their toes in the DIY USB device pool. Veterans may find a complete DIY joystick more up their alley and will be inspired by some plastic techniques as well.

Solving ISP problem with a Homebrew LTE Yagi

We’ve heard reports that internet connectivity in Australia can be an iffy proposition, and [deandob] seems to back that up. At the limit of a decent DSL connection and on the fringe of LTE, [deandob] decided to optimize the wireless connection with this homebrew Yagi antenna.

Officially known as the Yagi-Uda after its two Japanese inventors from the 1920s, but generally shortened to the name of its less involved but quicker to patent inventor, the Yagi is an antenna that provides high gain in one direction. That a homebrew antenna was even necessary at all is due to [deandob]’s ISP using the 2300MHz band rather than the more popular 2400MHz – plenty of cheap 2.4GHz antennas out there, but not so much with 2.3GHz. With multiple parallel and precisely sized and spaced parasitic elements, a Yagi can be a complicated design, but luckily for [deandob] the ham radio community has a good selection of Yagi design tools available. His final design uses an aluminum rod for a boom, 2mm steel wire for reflectors and directors, and a length of coax as the driven element. The result? Better connectivity that pushes his ISP throttling limit, and no more need to mount the modem high enough in his house to use the internal antenna.

People on the fringes of internet coverage go to great lengths to get connections, like this off-grid network bridge. Or if you’d rather use a homebrew Yagi to listen to meteors, that’s possible too.

Local Hacker Discovers Card Edge Connectors

When [turingbirds] was looking around for the absolute minimum connector for a JTAG adapter, he wanted something small, that didn’t require expensive adapters, and that could easily and reliably connect a few JTAG pins to a programmer. This, unsurprisingly, is a problem that’s been solved many times over, but that doesn’t mean there isn’t room for improvement. [turingbirds] found his better solution by looking at some old card edge connectors.

Instead of 0.1″ pitch pin headers, weirder and more expensive connectors, the Tag Connect, or even pogo pins, [turingbirds] came up with a JTAG adapter that required no additional parts, had a small footprint, and could be constructed out of trash usually found behind any busy hackerspace or garage. The connector is based on the venerable PCI connector, chopped up with a Dremel and soldered to a JTAG or ISP programmer.

This is simply a card edge connector, something the younglings seem to have forgotten. Back in the day, card edge connectors were a great way to connect peripherals, ports, and anything else to the outside world. They were keyed, and you could only put them in one way. They were relatively cheap, and with a big coil of ribbon cable, you could make custom adapters easily. For low-speed connections that will only be used a few times, it’s very hard to beat a card edge connector.

Of course the connector itself is only half of the actual build. To turn a chopped up PCI connector into a JTAG adapter, [turingbirds] made footprint and part files for his favorite PCB design tool. In this case it’s Eagle, and the libraries that will plop one of these connectors down are available on GitHub.

Is this the latest and greatest way to plug a programmer into a board? No, because this has been around for 30 or 40 years. It does, however, put a programming port on a PCB with zero dollars in components, a minimum of board footprint, and uses parts that can be salvaged from any pile of old computers.

High Voltage AVR Programmer

The most common way of programming AVR microcontrollers is the In System Programming port. That little six-pin header with MOSIs and MISOs coming out of it will program every AVR you’ll ever come across. The ISP does have a downside – fuses. Set your fuses wrong, and without a High Voltage Serial Programmer, your chip is bricked. [Dilshan] designed his own HVSP that’s less expensive than the Atmel STK500 and has a nice GUI app.

Instead of following in the footsteps of the USBtinyISP, [Dilshan] is using a PIC18F as the main microcontroller in the programmer. This chip was chosen because of its built-in USB functionality. Because the High Voltage part of a HVSP operates at 12V, actually providing that voltage needed to be taken into consideration. For this, [Dilshan] is using standard 78xx regulators with an 18V input.

The app to control this programmer does everything you would expect, including all the usual AVRdude commands. A great build, and just what we need to reset the fuses on a few dozen chips we have sitting around.

Flashing Chips With A CNC

[Eberhard] needed to flash several hundred ATMegas for a project he was working on. This was a problem, but the task did have a few things going for it that made automation easy. The boards the ‘Megas were soldered to weren’t depanelized yet, and he had a neat and weird bed of nails programming connector. There was also a CNC machine close by. This sounds like the ideal situation for automation, and it turns out the setup was pretty easy.

The boards in question were for FPV/radio control telemetry adapter and thankfully the assembly house didn’t depanelize the 40 PCBs on each board before shipping them out. A very cool ATMega flashing tool handled the electrical connections between the computer and the microcontroller, but a real, live human being was still required to move this flashing tool from one chip to the next, upload the firmware, and repeat the process all over again.

The solution came by putting a few metal pins in the bed of a CNC mill, 3D print an adapter for the flashing tool, and writing a little code to move the flashing tool from one chip to the next. An extremely simple app takes care of moving the programmer to an unflashed chip, uploading the firmware, and continuing on to the next chip.

There’s still some work to be done that would basically tie together the Gcode and AVRdude commands into a single interface, but even now a complete panel of 40 PCBs can be programmed in a little over 10 minutes. You can check out a video of that below.

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