power; the other end has a JTAG debug
header that is, unusually given the lack of
pre-populated general-purpose input/output
(GPIO), already populated with pins.
The primary retailer for the Longan Nano,
Seeed Studio, has added its own twist to
the design: a tiny 0.96in colour LCD panel.
It’s based on in-plane switching (IPS)
technology for improved viewing angles,
and it arrives pre-installed, though rather
precariously mounted via a double-sided
foam pad. A poorly made but serviceable
transparent plastic case is also included with
each purchase. There’s an RGB LED and a
micro-SD slot too, which are both welcome
additions. In particular, the latter allows
programs to access considerably more
storage than the 128KB of flash and 32KB
of static RAM (SRAM) on the GD32V.
The RGB LED, meanwhile, is covered by the
screen, but it’s still visible by reflection or by
viewing the board at an angle. Getting started
is also harder than necessary. A look through
the Sipeed developer documentation reveals
a list of udev rules that need to be installed on
a Linux host in order to recognise the board.
Once installed, the Longan Nano still fails to
operate – unless and until it’s booted into the
DFU bootloader by holding the Boot button
and toggling the Reset button.
That gets you a step closer, presenting the
device to the system, but the supplied udev
rules don’t cover the Longan Nano. To make it
actually work, you need to manually find the
vendor and product IDs via lsusb and add them
manually – noting, if you’re copying the line
above, that Sipeed places them in the rules list
in reverse order, with the product ID first.DangerousPrototypes teases Bus Pirate Ultra
Dangerous Prototypes has confirmed
that it’s working on an upgraded version
of its Bus Pirate universal bus interface
device, dubbed the Bus Pirate Ultra and
replacing the original device’s
microcontroller with a Lattice iCE40
field-programmable gate array (FPGA).
The Bus Pirate Ultra aims to achieve
the original device’s accomplishments,
allowing users to communicate with
hardware on a range of bus types, while adding considerably more features, including the
ability to drive an on-board colour LCD. No release date or pricing has yet been announced
for the Bus Pirate Ultra, but interested parties can visit dangerousprototypes.com/blog to
read about the device’s development process.N EWS I N BRI EF
Eventually, the Longan Nano will show up
as a usable DFU device. The next step is to
program it, using the Platform.io extension
to Microsoft’s free Visual Studio Code
integrated development environment.
Installation is easy, and three example
programs are included: simple LED blinkers
written in three different ways. Sadly, none
of them works until you manually modify
the configuration files to flash the Longan
Nano via DFU, rather than using the default
serial method. This isn’t mentioned in the
documentation either.
That documentation itself is also sparse.
There’s a lot more to be found if you go
digging around the company’s GitHub
repositories, but the bulk – including a handy
driver and example program for the bundled
LCD – is only available exclusively in Chinese.
It doesn’t all work either. The software
development kit allows you to program the
Longan Nano as a native GD32V device or
via an abstraction layer designed to offer
compatibility with Android sketches. While
the latter works for the simplest sketches,
anything more complex falls over. Using
printf is enough to abort compilation until
you edit the library by hand, and there
appears to be no way to open the UART
serial port in Arduino mode.
The small number of examples that are
available, though, show that there’s real
power in the device – and it’s hard to argue
with the price. For the beginner, the lack
of documentation makes it a no-go; for a
more experienced developer, particularly
one fluent in Chinese, the Longan Nano will
be a lot more tempting. The Longan Nano
is available now from seeedstudio.com for
$4.90 US (around £3.80 ex VAT).A debug header is pre-populated,
but not the general GPIO pinsThe LCD is serviceable, and fast enough for
basic animation tasks