VGA Output Hack on $2 PADI IoT Stamp & Other Realtek RTL8710AF Modules
It’s pretty amazing what you can do with those cheap WiFi modules coming from Espressif and Realtek. You may remember CNLohr getting ESP8266 to broadcast video to your TV though NTSC, and that was impressive. But developer kissste, who has been very active since the announcement of a $2 Realtek RTL8710 module, has now developed a VGA driver demo for Realtek Ameba WiFi SoCs, and successfully tested it on Pine64 PADI IoT Stamp.
Just like on ESP8266, there’s no hardware display block on RTL8710AF, RTL8711AF, and RTL8195AF SoCs, so instead he had to connect the signals to GPIOs with the video signal connected to GA1 via a resistor, H-Sync to GC2, and V-Sync to GA5. Video and H-Sync data is actually transfered over an SPI connection using DMA transfer for better performance. Normally the video signal for VGA is divided into red, green, and blue signal, so I understand he mixed all three into a single signal to output black or white on the display, and color is not possible at least not using 800×600 @ up to 63 Hz as possible in black & white.
Currently, the code just output some pre-defined characters once the board receives ATVG AT command, but you could modify the code – released on Github – to do whatever fancy stuff you want.