I am trying to determine how to use the PRU to control the DC motors on a BB Blue. I plan to use these 4 H-bridges to control two stepper motors. The PRU will generate the proper sequence of outputs to move the stepper at the proper speed, direction, and amount of rotation.
After examining the BB Blue schematic, I found I need to control the following signals: MDIR 1A, 1B, 2A, 2B, 3A, 3B, 4A & 4B, MOT_STBY, PWM 1A, 1B, 2A, & 2B.
After examining the Sitara Data Sheet, Table 4-1, I found I need to configure the device tree to set the modes as follows (for simplicity, only a subset of the signals shown):
Signal Signal name on Mode from Data
Octavo per BB Blue Sheet Table 4-1
schematic
MDIR 1A GPIO2_0_T13 7
MDIR 1B UART4_TX0_U17 6
MDIR 2A CP101_16_R13 7
MDIR 2B LCD_DATA14_V4 0
PWM 1A EHRPWM1A_U14 6
The mode setting I have chosen is the mode that causes the pin to have the signal name shown on the BB Blue schematic.
Do I have my mode settings correct?
I do not yet understand how to access the signals from the PRU…I will continue with that if I am correct so far. I do understand that I need to determine the host memory address for each signal. Am I on the right track?
Incidentally, assuming I understand the above, I have found what appear to be errors in the BB Blue Pin Table. I would like to correct it. How would I do that? I would like to submit my changes to someone (I’d colorize the cells I changed) who can verify what I’ve done before putting it in the wiki.
Clark