Characteristic which can send upto 200 bytes at a time

[HPC]

Hi

I just want to create a custom service with a characteristic, which sends "n" (upto 200) bytes at same time and this bytes are are written to a SD card via SPI

So my question is

1. Is there any limit on the number of bytes that can be transmitted via a characteristic,if yes ,how much?

2. Can I dynamically change the size of bytes in the characteristic?

Regards HpC

[Pål Håland]

Hi HPC,

Currently the Sofdevice only support 20 bytes sent as notifications or indications. This is because the MTU size is limited to 23 bytes (one for command code (notification) two for handle, and 20 bytes of data) What is needed is Extended MTU, something that is not supported as of now in the softdevice.

One other way of implement this is to fragment the packets, and you can use an offset or sequence number to tell how to reassemble the packets.

BR Pål

[John]

The fragmentation with sequence number is precisely how we are sending 2Kbytes of data at a time from our nRF51822 device to an iOS based app.