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Issue TWI lib for MAX32

Created Mon, 23 Nov 2015 22:19:09 +0000 by PICedh


Mon, 23 Nov 2015 22:19:09 +0000


The function Wire.requestFrom doesn't work with a board Chipkit Max32 if the length of the buffer requested is > 3 bytes. There is no such limitation with the board Chipkit Uno32 (I have tested the same program with both boards)

In fact the following statement in twi.c /twi_readFrom is looping because the interrupt doesn't set the status as idle

while(TW_IDLE != TW_STATUS) { asm volatile("nop"); }

Does someone already tested Wire lib with Max32 with a buffer > 3 bytes ?




Thu, 26 Nov 2015 21:39:55 +0000

Hi I have added in the wire lin a timeout of 10000 cycles in order to avoid blocking but I would like the issue with MAX32.


static volatile uint32_t twi_timeout; .... twi_timeout = 0; // wait for read operation to complete while((TW_IDLE != TW_STATUS) && (twi_timeout < 10000)) { asm volatile("nop"); twi_timeout++; } if (twi_timeout == 10000) return 0;


Thu, 26 Nov 2015 22:31:56 +0000

The timeout is a non-issue with the very latest version of Wire.h / DTWI.h. A bug was found recently which caused it to never return in certain circumstances. A timeout is not needed with the newest version since it always returns when it should.

If you want to grab the latest versions of the two libraries in question from github you are welcome to try them out:


Mon, 30 Nov 2015 20:08:51 +0000

Many thanks, it works on Max32 with the new lib