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Forum Index : Microcontroller and PC projects : SPI Problem
| Author | Message | ||||
| Frank N. Furter Guru  Joined: 28/05/2012 Location: GermanyPosts: 815 |
Hi everyone. I have to communicate with a TMC429 Steppercontroller via SPI. The registers are 32 Bits long! I read in the manual that the Bit-Range is limited to 23 because the range is limited by how many bits can be stored in a floating point number. I thought a single precision floating point number has 32 Bits??? 
Is there another way to send 32 Bits over SPI??? THANKS FOR HELP!!! Frank |
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| Dylan Regular Member  Joined: 17/06/2013 Location: NetherlandsPosts: 81 |
According to Appendix D, SPI sends bytes. But I'll leave it to experts on MMBasic and/or SPI. A single precision floating point number has 32 bits. Your problem is that some of these are used for the mantissa, and some for the exponent (and 1 for the sign). http://en.wikipedia.org/wiki/Ieee_float#Basic_formats and all that. |
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| MM_Wombat Senior Member  Joined: 12/12/2011 Location: AustraliaPosts: 139 |
Frank, When I had to send 32 bits to some chips via spi then I just sent two lots of 16 bits before I reset the latch. ie '32 bits to send &hff88 temp1=&hff temp2=&h88 Pin(17) = 0 'assert the enable line (active low) junk1 = SPI(18, 19, 20, temp1, H, 0, 16) junk1 = SPI(18, 19, 20, temp2, H, 0, 16) Pin(17) = 1 'reset the enable line (inactive high) maybe that would work.. Later I added some code to the source called spiDMD() which sent 32 bits each time, but was written to mirror the vga output to a Dot Matrix Display (DMD). Dennis [edit] I assume the latch is the nSCS_S pin, with the clock as SCK_S and SDI_S as data in with SDO_S as data out.. from the datasheet [/edit] Keep plugging away, it is fun learning But can be expensive (if you keep blowing things up). Maximite, ColourMaximite, MM+ |
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| Frank N. Furter Guru Joined: 28/05/2012 Location: GermanyPosts: 815 |
Hello Dennis, thank you very much! Your code works very well!!! 
I send four bytes with 8 bits with your (modified) code and can read all registers, I am very happy! 
Thanks again! :)Frank |
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