I am building a small two-wheeled robot using a Pololu DRV8835 dual motor driver, micro motors with wheel encoders and an Arduino UNO. I am trying to set up the DRV8835 in the IN/IN mode but am finding the truth table inscrutable. This is the table noted below (it doesn’t copy well) and found at pololu.com/catalog/product/2135. I have successfully used four DRV8801s in the past but somehow this table, despite considerable effort, has remained opaque to me. Can anyone help?
Thanks in advance. Please don’t tell me if every one else thinks it’s easy.
Drive/coast or drive/brake operation with MODE=0 (IN/IN)
xIN1 xIN2 xOUT1 xOUT2 operating mode
0 0 OPEN OPEN coast (outputs off)
0 PWM L PWM reverse/coast at speed PWM %
PWM 0 PWM L forward/coast at speed PWM %
PWM 1 L PWM reverse/brake at speed 100% − PWM %
1 PWM PWM L forward/brake at speed 100% − PWM %
1 1 L L brake low (outputs shorted to ground)
There is a lot of information in that table and it makes good sense to me, so is there something in particular that you don’t understand?
Does the table that precedes it (“simplified drive/brake operation with PHASE/ENABLE”) make sense? If so, what is it that you want to do with IN/IN mode, that the PHASE/ENABLE mode does not?
Thanks for your response. I’m having trouble with the logic and notation. Here’s my best guess as to what’s going on.
- The first row I think I get. Sending 0 to the IN pins results in opening the H-bridges so the motors will coast.
- In the second row if I send 0 to AIN1 and PWM to AIN1 I’ll get “L” in AOUT1 and PWM in AOUT1. What’s “L?”
- The third row gives me the same question.
- In row four, if I send PMW to AIN1 and 1 to AIN2 I get “L” in AOUT1 and negative PMW in AOUT2.
Am I getting it? Thanks for the help. I’m technically trained but a relative virgin to electronics.
“L” is low, essentially ground. So, when you see L on output 1 and PWM on output 2, output 2 is rapidly switched between high (H, essentially motor supply voltage) and low (L). Considering output 2, the motor is powered while it is at H and short-circuited or braked while it is at L.
Thanks, Jim. I think I’ve learned enough to give it a try. Be well.