I haven’t talked much about it (this being my first post and all…) but I’m pretty smitten with the current wave of RISC-V processors. I really like that it’s an open development platform, which means chip companies can buy or create the core that works with the basic instruction set and the programmers have a consistent and shared set of tools for the entire line ranging from $.10 parts for a home thermostat to a workstation class part. Rising tides and all that.
As a software guy, there are chip vendors that I’ve never heard of, but Bouffalolab Lab seems to be a pretty new name to most of us in the U.S. They’re making waves with the announcement of the BL602 and BL604 Systems-on-Chip (SOC). This part is just becoming available in the final week of October 2020 and it’s looking pretty interesting.
There are two parts in the immediate family: the BL602 and the BL604. The two parts differ by the number of GPIO pins and thus, the size of the external package. BL602 has 16 GPIOs and comes in a 32-pin QFP. The BL604 bumps to 23 GPIOs and rides in a 40-pin QFP. The 32-pin part should come in around 5mm per edge, so it’ll fit in really small applications. The integration is high enough that on the 32-pin part, half the pins are devoted to GPIO with the rest being the mandatory 3.3V, ground, crystal in, grounding, and other housekeeping. Outside the party, but similar enough that the SDK references them sometimes by accident, in the BL606 and 608. On those you go to ARM cores and trade wireless for audio, but that’s not our focus today.
It has 2.4Ghz radios, so that covers BTLE 5.0 and 802.11 b/g/n. Wi-Fi through WPA3 is supported. The microprocessor core runs at 192Mhz and comes from the SiFive cores. JTAG support is included and it claims support for the Segger family of debugging pods and software. It has 276K of SRAM, which is a really nice step up from the closest competing part, the GD32V’s which pack a mere 32K. Both parts have 128K of flash. There are two UARTs, but no USB controller like the GD32V. It has the standard alphabet soup that we expect in a post ESP8266 including SDIO, SPI, I2C, and such.
Bouffalo is a Chinese company and the documentation reflects that. Google Translate helps bring the doc and some code comments to us, but the reality is that many, many sections in the manual are just blank for now. The 34 page datasheet is oriented toward hardware developers, but does throw the smallest of bones to programmers. For example, it doesn’t tell you WHAT the UARTs are (it’s not a 16554) but it tells you where they are in memory.
A few companies are racing to put boards in the hands of developers. Both SiPeed and Pine64 seem to be early movers with prices hovering around $5USD with shipping being about as much again. I’m sure we’ll see an ocean of reference designs on Aliexpress and such soon. Currently, we have three such boards:
- Pine64’s PineCone64: USB-C (yay!) via a CH340N and with RGB LED.
- Doi.am’s DT-BL10: Micro USB
- SiPeed’s BL602: Micro USB. Rumored to have FTDI serial interface. Might be same as Doi.am’s
Development environments include Eclipse + OpenOCD or Freedom Studio + OpenOCD. The company provides an app called DevCube (unrelated to the VR tool of the same name) to configure devices for production. This helps IoT makers prepare the flash for partitioning and OTA upgrades. It seems inevitable that the popular PlatformIO IDE will be supported. Since it’s a familiar SiFive core, just submitting the needed flash layout and programming data is probably on the order of dozens of lines of code to support PlatformIO for BL602/BL606.
If we look past the large number of blank doc pages and the high percentage of Chinese in the SDK, what do we find? This is actually the jackpot for RISC-V designs – there are working Mac, Linux, and Windows (Cygwin) GNU-based toolchains right in the tree at launch. Filenames are a bizarre mix of CamelCase and underscore_separators, even sometimes in the same directory. It ships with GCC 8.3, but since RISC-V was upstreamed a while ago, I’d expect upgrading to later versions to be easy. It relies heavily on Amazon’s FreeRTOS as the core. The entire package relies on external source (FreeRTOS, GNU Tool binaries, compression libs, etc.) by copying and not via git-referencing the modules by inclusion. This means you’re probably always on a stable build, but it also almost insures that you’ll always be behind releases of third party code, which can be bad in network-connected devices. Amazon’s MQTT and Jobs interfaces are well represented. The expected libraries for a high-functioning 32-bit core are all there, with a pretty full ANSI libc with printf, compression and a filesystem for the flash. Startup code is a pretty straight SiFive example for GCC. There are 31 separately buildable apps for demonstrating features of the device, including a CLI for interfacing with it somewhat like boot monitors of days past. “Hello, World” is there, of course, but ironically doesn’t contain the string “hello” as it gets printed in a callback from the initialization state machine as it advances.
The network modules are, unfortunately, binary blobs at this time. I expect the community to make short work of changing that.
Overall, this looks like a good entry for the bottom/low-end space for wirelessly connected (or not) devices for hobbyist and commercial applications. The SiFive core is well regarded for performance and the performance should be better than the GD32V’s 108Mhz while the price lower than the AI-centric dual-core 64-bit Kendryte K210.
Official Boufallo SDK
Pine64 is offering hardware to developers that help get BL602 started.
SiPeed (makers of Longnan and Maix lines) has a BL602 SDK.
Doit has a $4 eval board with a BL602 SDK.
All three of those are forks from the Boufallo code. We don’t know yet how different the hardware is.