Messages

1

General Discussion / Re: attiny841 in tinyshield dual motor

« on: January 01, 2017, 06:06:32 AM »

Hi Ben, just pick up the attiny841 recently again. I was able to load the firmware. what is the fuse and lock bits setting used in tinyshield dual motor?   High bits, low bits, Extended bits and LB bits 

2

General Discussion / Re: attiny841 in tinyshield dual motor

« on: January 22, 2016, 03:52:22 AM »

Hi Ben,

I am using following programmer, cable and attiny841 shield to program attiny841.

http://www.protostack.com/accessories/usbasp-avr-programmer
https://www.sparkfun.com/products/9215
https://www.tindie.com/products/bot_thoughts/eezeetiny841/

I install winavr and import main.c and makefile. But compilation failed and it complaint about unknown MCU 'attiny841' specified.  As you said, look like avrdude need an addition for attiny841. Can you help on how to add the addition to let winavr or avrdude to recognize and support attiny841 

3

General Discussion / Re: attiny841 in tinyshield dual motor

« on: December 29, 2015, 01:04:25 AM »

Hi Ben,

Thanks for helping!!  I found the firmware zip in the library.  Very nice work of firmware coding!!!

- I always use arduino sdk to load the program into arduino board.  Just want to learn, how can you load the firmware into attiny841.  what kind of the software and what kind of cable need to be used to load the firmware into attiny841? any good link for learning that?

- For pwm, for example, I set the MaxPwm to 255 and use 3.7V for VM.  when I use  motor.setMotor(1, 125), I assume that the driver output should be around 1.85V. But when use mulimeter to measure it, it is actually 3.0V.  is it possible that the motor driver drv8837 itself does not provide  linear output.

- Also, when I set motor.setMotor(1, 255), max driver output only 3.2V out of 3.7V.  I wonder if drv8837 has high resistant of mosfet which eat up some voltage. Here are two observation. 
      1) Connect driver 2 output pins to motor, max is 3.2V 
      2) Since my motor only drive in one direction,  I connect Vbatt (3.7) directly to motor(+)pin while connect only one driver output pin(low) to motor(-), now max can archive ~3.5V.  It concludes that drive8837 internal each mosfet might eat up around 0.25-0.3V. 

4

General Discussion / attiny841 in tinyshield dual motor

« on: December 19, 2015, 10:27:00 PM »

Anyone know how those command are being interpreted. Those command address are not register address in attiny841 datasheet. Are those commands pre-programmed in attiny841?  where can I find the "code" being used to interpret those command?  Current problem I have is 0-MaxPwm is not linearly proportional to 0-Vmax range output. I wonder if there is some issue in the "code" which interpret the command.

MotorDriver.cpp

  writeByte(COMMAND_SET_MODE, MODE_COMMAND);//send interpreted commands- see header file
  writeByte(COMMAND_CLOCK_PRESCALER, T841_CLOCK_PRESCALER_1);
  writeByte(COMMAND_PRESCALER_1, T841_TIMER_PRESCALER_1);
  writeByte(COMMAND_PRESCALER_2, T841_TIMER_PRESCALER_1);
  writeCommand(COMMAND_TIMER_1, PWMperiod);
  writeCommand(COMMAND_TIMER_2, PWMperiod);
  writeByte(COMMAND_SET_FAILSAFE_PRESCALER, T841_TIMER_PRESCALER_8);