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ADS131EXX driver for the BeagleBone Black

PRU driver for the ADS131EXX ADC/AFE IC from Texas Instrument

Includes:

  • PRU SPI driver driver (spi.inc) that can be used independently (follow steps 1 and 2 below)
  • Main definitions of the ADS131EXX IC (ads131_defs.inc)
  • Driver for the ADS131E08 (8 channels version of the IC, ads131e08.inc)

Use

  1. Define SPI_SCLK, SPI_MOSI, SPI_MISO, and SPI_CS pins. For instance,
  SPI_SCLK      .set  5       ; PRU1_5 GPIO2_11 P8_42
  SPI_MOSI      .set  0       ; PRU1_0 GPIO2_6  P8_45
  SPI_MISO      .set  3       ; PRU1_3 GPIO2_9  P8_44
  SPI_CS        .set  7       ; PRU1_7 GPIO2_13 P8_40
  1. Define SPI_SCLK_DELAY to set the SPI clock frequency using the formula SPI_SCLK_DELAY = floor( (t_SCLK / 5 ns) / 4 ) and SPI_SCLK_DELAY >= 3, where t_SCLK is the SPI clock period. For instance,
  SPI_SCLK_DELAY  .set  9
  1. Define ADS_START, ADS_RESET, and ADS_DRDY pins. For instance,
  ADS_START     .set  4       ; PRU1_4 GPIO2_10 P8_41
  ADS_RESET     .set  2       ; PRU1_2 GPIO2_8  P8_43
  ADS_DRDY      .set  1       ; PRU1_1 GPIO2_7  P8_46
  1. Include the ads131e08.inc:
  .include "ads131e08.inc"

Functions descriptions

SPI (API)

  • SPI_TX: Transmit byte from spi_tx_reg
    • Arguments:
      • spi_tx_reg (input, register): register holding the byte to transmit (e.g., r1.b0)
    • Side effects:
      • Modifies r29
  • SPI_RX: Receive byte into spi_rx_reg
    • Arguments:
      • spi_rx_reg (output, register): register byte in which to record received data (e.g., r1.b0)
    • Side effects:
      • Modifies r29

SPI (INTERNAL)

  • NOP: No operation (not in the PRU assembly language)
    • Arguments: none
    • Side effects: none
  • SPI_WAIT: Pauses for 2*spi_wait_delay - spi_wait_stop_early instructions (5 ns each)
    • Arguments:
      • spi_wait_delay (input, immediate)
      • spi_wait_stop_early (input, immediate)
    • Side effects:
      • Modifies r29
  • LBIT: Load bit lbit_bit1 of register lbit_reg1 to bit lbit_bit2 of register lbit_reg2
    • Arguments:
      • lbit_reg1 (input, register): Source register
      • lbit_bit1 (input, immediate): Source register bit
      • lbit_reg2 (output, register): Destination register
      • lbit_bit2 (output, immediate): Destination register bit
    • Side effects: none
  • SPI_TX_CLK: SPI clock pulse during data transmission
    • Arguments: none
    • Side effects:
      • Modifies r29
  • SPI_RX_CLK: SPI clock pulse during data reception
    • Arguments: none
    • Side effects:
      • Modifies r29

ADS131E08 (API)

  • ADS_WAIT: Pauses for 2*ads_wait_n instructions (5 ns each)
    • Arguments:
      • ads_wait_n (input, immediate)
    • Side effects:
      • Modifies r28
  • ADS_STARTUP: Start up routine of the ADS131 IC (stops conversion, resets IC, stop continuous data conversion)
    • Arguments: none
    • Side effects:
      • Modifies r28
  • ADS_SEND_CMD: Send command ads_send_cmd_command to ADS131
    • Arguments
      • ads_send_cmd_command (input, immediate):
    • Side effects:
      • Modifies r28
  • ADS_WRITE_REG: Write ads_write_reg_data to ADS131 register ads_write_reg_addr
    • Arguments:
      • ads_write_reg_addr (input, immediate): ADS131 register address
      • ads_write_reg_data (input, immediate): Data to be written in ADS131 register
    • Side effects:
      • Modifies r28
  • ADS_READ_REG: Read ADS131 register ads_read_reg_addr into ads_read_reg_data
    • Arguments:
      • ads_read_reg_addr (input, immediate): ADS131 register address
      • ads_read_reg_data (output, register byte): Register byte to save ADS131 register data (e.g., r1.b0)
    • Side effects:
      • Modifies r28
  • ADS_GET_DATA16: Receive data packet from ADS131
    • Arguments:
      • ads_get_data16_reg1 (output, register): Register containing STATUS packet (24 bits)
      • ads_get_data16_reg2 (output, register): Register containing data from channel 1 (.b3 and .b2) and channel 2 (.b1 and .b0)
      • ads_get_data16_reg3 (output, register): Register containing data from channel 3 (.b3 and .b2) and channel 4 (.b1 and .b0)
      • ads_get_data16_reg4 (output, register): Register containing data from channel 5 (.b3 and .b2) and channel 6 (.b1 and .b0)
      • ads_get_data16_reg5 (output, register): Register containing data from channel 7 (.b3 and .b2) and channel 8 (.b1 and .b0)
    • Side effects:
      • Modifies r28
  • ADS_READ_ALL: Read in all ADS131 registers in a single call
    • Arguments:
      • ads_read_all_id (output, register): Register byte containing ADS131 register ID
      • ads_read_all_config1 (output, register): Register byte containing ADS131 register CONFIG1
      • ads_read_all_config2 (output, register): Register byte containing ADS131 register CONFIG2
      • ads_read_all_config3 (output, register): Register byte containing ADS131 register CONFIG3
      • ads_read_all_fault (output, register): Register byte containing ADS131 register FAULT
      • ads_read_all_ch1set (output, register): Register byte containing ADS131 register CH1SET
      • ads_read_all_ch2set (output, register): Register byte containing ADS131 register CH2SET
      • ads_read_all_ch3set (output, register): Register byte containing ADS131 register CH3SET
      • ads_read_all_ch4set (output, register): Register byte containing ADS131 register CH4SET
      • ads_read_all_ch5set (output, register): Register byte containing ADS131 register CH5SET
      • ads_read_all_ch6set (output, register): Register byte containing ADS131 register CH6SET
      • ads_read_all_ch7set (output, register): Register byte containing ADS131 register CH7SET
      • ads_read_all_ch8set (output, register): Register byte containing ADS131 register CH8SET
      • ads_read_all_fault_statp (output, register): Register byte containing ADS131 register STAT_P
      • ads_read_all_fault_statn (output, register): Register byte containing ADS131 register STAT_N
      • ads_read_all_gpio (output, register): Register byte containing ADS131 register GPIO
    • Side effects:
      • Modifies r28

ADS131E08 (INTERNAL)

  • ADS_INIT: Initializes the SPI driver interface. To save memory, the ADS131 driver uses jumps (JMP) to call SPI_RX and SPI_TX as if they were functions instead of using inline code. The input to SPI_TX and the output of SPI_RX must be saved in r28.b0 and the return address must be in r28.w2
    • Arguments: none
    • Side effects:
      • Modifies r28