Maximum length of BT service characteristic value

[espruino-discuss3]

Posted at 2019-01-26 by JPep

I'm trying to put more than 22 characters into a bluetooth service characteristic value. I can see from targets/esp32/BLE/esp32_gatts_func.h that the maximum value is defined as 22 however this value is never referred to again in code (at least I can't see where it is). When I try to fit a string of more than 22 characters it repeats 22 characters of the longer value.

Anyone had any luck presenting a value longer than 22 characters?

I'm using the Device Name org.bluetooth.characteristic.gap.device_name 0x2A00 characteristic with code something like:

-- snip

0x2A00 : {	
	value: "123456789abcdefghijklmnopqrstuvwxyz",
	maxLen : 127,  //this has no effect
	readable : true, 
	description: "123456789abcdefghijklmnopqrstuvwxyz"
}

-- snip

p.s. Loving Espruino, it's fantastic. Keep up the excellent work.

[espruino-discuss3]

Posted at 2019-01-27 by JumJum

ESP32 uses some firmware already on chip (ROM) and some precompiled libs for BT
I'm pretty sure, 22 limit is hidden there
In latest ESP-IDF- versions, some functions from ROM are moved to flash. This is one reason why size of binaries increased that much.
Not helpful for you (sorry), but at least you know why we have these, and other, limits

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Posted at 2019-01-27 by JPep

Ah, that explains it. That's a pity... Thanks for the info!