On VoCore2 Ultimate dock, we have a chip GD32F150G8U6 which is used as USB2TTL chip, so we can login to VoCore2 console through USB.
But GD32F150G8U6 has much more function than just USB2TTL, it has AD/DA convert inside. We can disable USB2TTL and switch it to AD/DA function. VoCore2 UART2 can be used to get AD/DA data from GD32F150.
This is current dock GD32F150 part of sch, PA0-PA7 and BOOT are exported; TXD/RXD are connected to VoCore2; USB DM/DP are connected to microUSB on dock.
In order to make AD/DA work, need to write a small firmware for GD32F150. we have toolchain already, use ARM-M3 default toolchain, link is here: https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/gnu-rm/downloads
Also we need some library to help us use the chip. GD32F150 library I upload to the blog server, can download here: http://vonger.cn/misc/vocore2/GD32F1x0_Firmware_Library_v3.1.0.rar
Once compiled finish, we can use gd32up to load it to chip(do not forget to set the BOOT pin to high-5V when flash firmware), source code at github.com/vonger/gd32tools, this one can be compiled by VoCore2 toolchain gcc and run in VoCore2 directly.
note: better to set UART2 port band rate to 9600 or lower, because MT7628 do not have a precisely clock on UART.
Here are some examples source code about GD32F150: http://vonger.cn/misc/vocore2/GD32150G8U6.HSI.zip
VoCore2 Ultimate is using example 22_USB_VirtualComPort, I modified its USB pull up pin in usb_hwp.c to GPIOA,GPIO_PIN_13 to fit the hardware.
To be continue… later I will try to write a demo code about AD/DA firmware.If you want to try it first, check example 18_ADC_conversion_triggered_by_timer and 19_DAC_Digital_To_Analog_Conversion