This C library describes the control of the 16-channel AD converter MAX11131 via SPI with a microcontroller of the MSP430 series. The MSP43F5359 is used as a microcontroller and the IAR Embedded Workbench is used as a development environment.
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Short description MAX11131
The MAX11131 ad converter has write and read commands and can be addressed via SPI. The chip select line signals the start and end of a frame. The MAX11131 offers the possibility to use either 16 channels as single ended or 8 channels differential.
All functions of the library “max11131.c” are explained below:
| void MAX11131_SPI_init(void) | |
| Initializes the SPI interface for channel UCA1 of the MSP430F5359 | |
| Parameter | – |
| Return | – |
| unsigned char MAX11131_SPI_transmit(unsigned char data) | ||
| Send and receive via SPI via channel UCA1 of the MSP430F5359 | ||
| Parameter | data | Information to be sent via SPI |
| Return | Information received via SPI | |
| unsigned int MAX11131_transmit(unsigned int command) | ||
| Sends and receives to and from the MAX11131 via the SPI interface. For the commands, see the Defines and datasheet which start on page 15. Note that a 2 byte command is sent. Depending on the command, an answer can be received. The answer must however be the last command which has been dispatched and will not be the actual shipping | ||
| Parameter | command | Command to be sent to the MAX11131 |
| Return | Answer received from the MAX11131 | |
| MAX11131_bipolar_chanel(char k) | ||
| Function should only be used internally. Switch instruction to select the bipolar channel | ||
| Parameter | k | Channel to be selected |
| Return | Returns the corresponding register | |
| unsigned int MAX11131_range_chanel(char k) | ||
| Function should only be used internally. Switch instruction to select the range channel | ||
| Parameter | k | Channel to be selected |
| Return | Returns the corresponding register | |
| unsigned int MAX11131_unipolar_chanel(char k) | ||
| Function should only be used internally. Switch instruction to select the unipolar channel | ||
| Parameter | k | Channel to be selected |
| Return | Returns the corresponding register | |
| unsigned int MAX11131_csel_chanel(char k) | ||
| Function should only be used internally. Switch instruction to select the AD channels | ||
| Parameter | k | Channel to be selected |
| Return | Returns the corresponding register | |
| void MAX11131_Echo_aktiv (char status) | ||
| Activates the echo function of the MAX11131 for the config registers. Here: Activate echo -> Send new config at time t -> Send again new config at time t + 1 and get as echo of MISO the config from time t if everything has expired correctly. | ||
| Parameter | status | If TRUE, echo is active, but not for FALSE |
| Return | – | |
| void MAX11131_test (void) | |
| Test the MAX 11131 by sending an echo and then a config, as a result should come 0x8380 | |
| Parameter | – |
| Return | – |
| void MAX11131_ADC_conf(void) | |
| The function sets the AD converter. To do this, the user must manipulate the #defines in the header file (see also below). The procedure is taken from the flow chart on page 32; MAX11131 Specifications; Year 2015.
Variable GLOBAL in the header and edit if necessary (TRUE or FALSE) RefSel = TRUE: Single-Ebded reference; FALSE: Different reference SoP_FD = TRUE: Pseudo or Single-Ended; FALSE: Full-Differential SinEnd = TRUE: Single-ended; FALSE: Pseudo-Differential UniBip = TRUE: Unipolar; FALSE: Bipolar Ran = TRUE: reference +/- Vref; Reference +/- Vref / 2; Only for bipolar of interest Num = number of channels, select between 0 to 7 |
|
| Parameter | – |
| Return | – |
| void MAX11131_init(void) | |
| Initialize the MAX11131 by first configuring it and then reading dummy values | |
| Parameter | – |
| Return | – |
| unsigned int MAX11131_get_ADC_eins(char ch) | ||
| AD value from single channel | ||
| Parameter | ch | Channel to be selected |
| Return | Returns the appropriate AD value | |
| unsigned int* MAX11131_get_ADC(char start, char end) | ||
| Refer to “Figure 12 / Data Sheet Page 33”. Here, there are too many possibilities to handle the function with TRUE / FALSE, like before. I chose the one that was suitable to my project. These are: External Clock, Manual, Channel Selection, No Reset, Power-Mode Normal. The channel / channels have to be selected by “start” and “end”.
!!! If I measure several channels, then note: Now I measure for channel N and get the value of channel N-1 first !! |
||
| Parameter | start
end |
From initial channel to
End channel |
| Return | Returns AD value array | |
| unsigned int MAX11131_mean(char ch, int cnt, int pow) | ||
| Calculate mean value for the respective channel <ch> with shift-division (time-saving than normal division). Pay attention to the <cnt = multiple of 2> and <pow>. | ||
| Parameter | ch
cnt pow |
Channel to be averaged
Number of values (must be multiples of 2 -> 2 ^ n) The power n |
| Return | Returns the mean value | |