Add screenshot function

[andimik]

Some months ago, I suggested a screenshot function for TEF6686. As I am playing with another small radio with SI4732 chip, I found out that this radio supports it via serial connection.

So I decided to open a new discussion.

Steps:

sudo chmod o+rw /dev/ttyACM0

cat /dev/ttyACM0 > /tmp/dump.raw

send a C to serial
echo -e "C" > /dev/ttyACM0

Then process the raw dump and save as bitmap

xxd -r -p < /tmp/dump.raw > /tmp/dump.bmp

Here is the source code:

esp32-si4732/ats-mini@c0fdd30

[lvxc88]

I roughly tested it and found that using tft. readPixel (x, y) cannot retrieve pixel values. Using Sprite is possible, but ESP32-WROOM-32U memory is too small to use a full screen Sprite, so it seems impossible to achieve screenshot

[lvxc88]

The radio of si4732 seems to be using the S3 with larger memory, and its screen size is smaller, so it is feasible for him to use Sprite for screen capture

[PE5PVB]

Sorry, this is just not possible because of limited SRAM.