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)

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

2. 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

3. 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

4. Include the ads131e08.inc:

  .include "ads131e08.inc"

• 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

• 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

• 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

• 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