Hi, We are trying to use the McBSP to interface to a UART. we followed the application report document (SPRA633A) for TI. For a loop back mode it works fine, we get what ever we sent. Connecting to a serial PC port it seems we are missing the first 2 bits and the data is completely out of Synch. Any idea what could be the cause? Thanks. |
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McBSP & UART
Started by ●June 24, 2002
Reply by ●June 24, 20022002-06-24
I have not looked at the SPRA document in a while, but we had some severe problems with the first iteration of the document. Indeed the revision of the document we used last year (SPRA633 without the A) had typo's in the example code!! We ended having better success writing our own driver from scratch. Here are a couple of issues and mistakes we made which caused problems in our attempts using our own code: 1) We initially used some bitwise & and | operators on the some write only EDMA registers which really messed things up. 2) We had a lot of difficulty having our EDMA bit buffers off chip. The problem was EDMA would write directly to offchip memory and if you did not tell the processor to resolve the cache mis-match we we would generally find the first bit or two wrong. The easy fix is to configure the processor to 1/4 sram and 3/4 Cache and then EDMA the bits into on-chip memory (or do not use cache at all which would be a waste). A more difficult fix is to tell the processor to resolve the cache mis-match in the EDMA ISR, wait for the mis-match to resolve and then convert the bits into bytes. Once we moved beyond these two major issues our own driver seemed to work well. Incidently we used the on-chip clock to drive the mcbsp and had to use 32 bit wide words for bit frames rather than 16 bit to cover the baud rates we needed. -----Original Message----- From: [mailto:] Sent: Monday, June 24, 2002 9:23 AM To: Subject: [c6x] McBSP & UART Hi, We are trying to use the McBSP to interface to a UART. we followed the application report document (SPRA633A) for TI. For a loop back mode it works fine, we get what ever we sent. Connecting to a serial PC port it seems we are missing the first 2 bits and the data is completely out of Synch. Any idea what could be the cause? Thanks. _____________________________________ Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer. You need to do a "reply all" if you want your answer to be distributed to the entire group. _____________________________________ About this discussion group: To Join: Send an email to To Post: Send an email to To Leave: Send an email to Archives: http://www.yahoogroups.com/group/c6x Other Groups: http://www.dsprelated.com ">http://docs.yahoo.com/info/terms/ |
Reply by ●June 24, 20022002-06-24
Hi all, I am using DSK6211 kit with codec TLC320AD535. I am facing a problem here. When I feed a digital signal (such as negative square wave 0 to -1) to the DAC ( by McBSP_write() function) the analog waveform as seen at the output of the DAC in an oscillator comes to be exactly opposite to what is expected ( a square wave of 0V to 1V). But, when a feed a positive signal of ( 0V - 1V) the waveform obtained at the output is ( -0.5V to 0.5V). The signal gets shifted equally around the x-axis. Please help. Purushottam. |