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Sign Extension not working?

Question asked by Dano on Oct 9, 2011

Hello all,


I am using the BF506F internal A2D trying to sample a sine wave with DC level of 2.5V.

I am configuring the ACM to single mode, RANGE=1, and then the following SPORT configuration:


*pSPORT1_RCR2     =SLEN(15);  // SLEN (Serial Word Length)
*pSPORT1_RCR1     =0x5405;       // LRFS|RFSR|RSPEN|RDTYPE=sign extension


*pACM_ER0    =0x0031; // Single Ended|Va1|Enable Event

*pDMA4_CONFIG =0x0086; // Data Interrupt|16Bit Word|Memory Write
*pDMA4_START_ADDR =(void*)Rx_Buffer;
*pDMA4_X_MODIFY =2; // 2 Strides
*pDMA4_X_COUNT    =FFTSIZE; // FFTSIZE Samples transfer
*pDMA4_CONFIG |=DMAEN; // DMA Enable

Unfortunately, I never get the sign extended properly, and it seems that the MSB (15th bit) is always zero regardless of the RDTYPE.

Please see the picture attached.



Please Help!