Blog of spblinux

Board specifications at http://dl.sipeed.com/MAIX/HDK/Maix-GO/Maix-GO_2.20/ and available at https://www.seeedstudio.com/Sipeed-MAIX-GO-Suit-MAIX-GO-2-8-inch-LCD-ov2640-with-M12-lens-p-2874.html.

Example code in language c can be found at

• https://github.com/GitJer/Some-Sipeed-MAIX-GO-k210-stuff.
• https://github.com/sipeed/LicheeDan_K210_examples.
• https://github.com/kendryte/kendryte-standalone-demo.

Reference

• Most current (use google translate) https://github.com/kendryte/kendryte-doc-standalone-programming-guide/tree/master/zh-Hans.
• english version (reduced content):
• kendryte download page: pdf versions of documentations and sdk toolchain download: https://kendryte.com/downloads/.
• … best guide is open source code (of sdk):
  • libs https://github.com/kendryte/kendryte-standalone-sdk/tree/develop/lib/drivers and
  • headers https://github.com/kendryte/kendryte-standalone-sdk/tree/develop/lib/drivers/include.
• Some more information can be found in forums of kendryte and sipeed: https://forum.kendryte.com/category/4/sdk and https://bbs.sipeed.com/.

Download kendryte-standalone-sdk, kendryte-standalone-demo and kendryte-gnu-toolchain and kflash (needs python3; pip3 install pyserial pyelftools kflash; windows kflash)

• if both are installed inside directory $HOME/kendryte/
  • cd kendryte/kendryte-standalone-sdk/build/
  • cmake .. -DTOOLCHAIN=$HOME/kendryte/kendryte-gnu-toolchain/bin/ -DPROJ=apu
  • make
  • kflash -p /dev/cu.usbserial-00004014B -B goE apu.bin -b 2000000
  • replace /dev/cu.usbserial-00004014B by your usb port (second port of the two ports of maiix go has to be used)

Playing with builtin APU (audio processing unit) and circular mic array (6 mics + center mic; specs, buy)

+----------+ 　+----------+ 　+------------+ 　+-------+ 　+-----+　+--------------------- + 　+-----+ 　+-----+
 | 8ch in | - > | buffer | - > | DAS BF | -> | gain | -> | FIR | -> | DownSample | -> | FIR | -> | FFT |
 +----------+　 +----------+ 　+------------+ 　+-------+ 　+------+　+---------------------+ 　+------+　+------+

• schema shown above is info about APU pipeline from forum
• playing with APU_VOC output really needs a scope (using wires soldered to outputs of DAC chip)
• i2s_set_sample_rate: input uses 4 stereo channels, output uses 1 stereo channel, so sample rate of input must be 4 times higher than output rate. (APU_VOC buffer has 256 samples of 32bit =16bit left+16bit right.)
• Using mics without apu: https://github.com/GitJer/Some-Sipeed-MAIX-GO-k210-stuff/tree/master/src/mics_and_lights_on_array
• Basic sdk demo using apu: https://github.com/kendryte/kendryte-standalone-demo/tree/develop/apu.
• Forum discussion about it: https://forum.kendryte.com/topic/352/apu-configuration.
• Online tool to calculate FIR filter coefficients: http://t-filter.engineerjs.com/.
  • Reference: https://sites.google.com/site/firfiltercoefficientsexc/
  • See separate post