Hi,
I'm working with a BT817 and I've encountered a strange issue with ROM fonts.
According to the documentation, the BT817/8 has built-in ROM fonts with handles 16–34, and fonts 31–34 are large ROM fonts encoded in ASTC 8x8 format.
However, on my system:
EVE_CMD_TEXT(20, 10, 31, 0, "BT817 Flash Image"); // works
EVE_CMD_TEXT(20, 10, 32, 0, "BT817 Flash Image"); // BT817 freezes
Font 31 works correctly, but as soon as I use font 32 (or any handle >31), the BT817 co-processor appears to hang (command FIFO stops progressing).
External flash is working correctly and is in FAST/FULL mode — I can read images from it without any issues.
I'm not sure whether I'll actually need these ROM fonts since I'll probably use custom fonts anyway, but I'd like to understand whether this is a known issue, a configuration mistake on my side, or possibly a silicon/firmware bug.
Thanks in advance for any advice.
Hi,
For these fonts, it is required to use CMD_ROMFONT. Please see section 5.70 in the Programming Guide for examples.
https://brtchip.com/wp-content/uploads/2025/07/BRT_AN_033_BT81X-Series-Programming-Guide.pdf
Here we set the font 34 to user handle 1.
cmd_romfont(1, 34);
cmd_text(60, 32, 1, 0, "34");
Hope it helps, Best Regards, BRT Community
To add a minor detail, FT8xx and BT81x "only" support 32 bitmap handles, so 0 to 31.
15 is used as a scratch bitmap by a couple of commands.
BT82x has 64 bitmap handles and 16 to 34 are assigned to the fonts.
Unfortunately it still uses the same fonts, but at least there are all directly useable.