nrf52832 spi master's max transfer size at once is 255

[pipixia_1_1]

hi 

im using nrf52832 to driver my lcd by spi，so i need a high speed.but when i use its spi ，i found the length of spi is limited to 255 bytles .i browse other developer's post ablout the question ，

the answer given is that 52832's max length of spi transfer at once  is 255 bytles. and i see this post

https://devzone.nordicsemi.com/f/nordic-q-a/30368/nrf52840-spi-transfer-buffer-length

to know that 52840 can  more than 255 bytles at sdk15,now i use sdk15.3 to develop my product .so i want to know if i can change the limit ,let it beyond 255 bytles by modif soft at sdk15.3 ?

thanks!

[awneil]

AIUI, This is a limit of the nRF52832 hardware - you can't get around it in software (other than by sending multiple 256-byte transmissions)

I think the nRF52810 also has the larger transfer capability - if your application will fit within its other constraints ...

[pipixia_1_1]

thanks for your reply,what make me confuse is that other company's product' screen  slip very fast by 52832. as you say ,i really dont know how does  they do it.

[awneil]

pipixia_1_1 said:

what make me confuse is that other company's product' screen  slip very fast by 52832

I don't understand what you mean by that.

AIUI, The 256-byte limit is just the maximum you can do in a single DMA transfer - it doesn't mean that the nRF52832 can never transmit more than 256 bytes!

As noted earlier, you can simply use multiple transfers when you need >256 bytes total.

[pipixia_1_1]

yes ,it can never a transmit after 256 bytes,but once my data divide some times to transfer,the totality send time will increase，in other words，the  totality  speed will reduce .tanks for your reply.

[pipixia_1_1]

new a transmit

[awneil]

pipixia_1_1 said:

it can never a transmit after 256 bytes

Nonsense - of course it can!

pipixia_1_1 said:

once my data divide some times to transfer,the totality send time will increase

Yes, of course it will - but that will not necessarily be a problem!

pipixia_1_1 said:

the  totality  speed will reduce

Yes - but, so long as it doesn't reduce by too much, that won't matter!

Which is undoubtedly what these "other company's product" are doing.

I haven't tried it - does the DMA support double-buffering ... ?