SN 163 not working

[J Thorpe]

After initial assembly the majority of the unit worked with exception of a couple of buttons. A methodical inspection of the board and and a re-read of the instructions identified a number of resistors I had not installed, R113 thru R116. The resistors were installed and then nothing worked. At turn on I get a beep and if I push any button decimal points on the displays light up. Reading the other repair/not working threads I replaced the HT16k33A from two different sources with with different lot numbers. The behavior did not change. When I looked at the NANO pins with a scope there is no activity on any of the lines. The nano has power and the clock osc. is running . I’m not sure where to go next.

[me2016]

The missing resistors would cause the keyboard to not work but it wouldn’t destroy anything.
When you looked at the board with your scope, look at the i2c pins, they should always be busy. If not, hit the reset button on the nano an see if that helps.

Make sure that it’s no shorts anywhere, starting with the pins on ht16k33a. If you replaced the chip it may be that the new chip is from a bad version (I had to get 3 batches before I got one working).

Try to get a connection to a pc so you can see what the arduino reports on boot, remember to set the speed to 38400 (max speed for a 3.3V arduino).

If you don’t use external power, make sure the batteries are good, pref not rechargable (1.2V) but some alkaline or lithium (1.5V).

[J Thorpe]

There is no activity on the i2c lines, they stay high. The nano reset does not change anything. I will try to monitor the nano on start-up, I’m not sure how to do it but I will give it a try. The batteries are fine.

[J Thorpe]

Progress!! A friend programmed a new Arduino for me. The unit now functions. The turn on sequence seems different so I’m not sure the software is completely correct. Also, it seems to draw a lot of current, .25 amps at 3.0 volts during standby. The current jumps way up during turn on when all the LEDs come on. The unit is basically not usable with the AA cells. External power works fine. Any comments or suggestions.

[me2016]

Currently on the road but will be back next week and then I will take some measurements. I’m using it with 2 NiMH AA cells that works fine, at least when they are fully charged. Of course having 1.5v alkaline would be better.
I also plan on program an arduino and send to you but not sure if I have any spare to do that with.

[J Thorpe]

I checked the discharge characteristics of alkaline AA batteries and they should last about 2hrs at a 0.5 amp rate so the batteries should work fine, I was just surprised by the current draw. I suspect my meter is reading peak, I need one of my old VOMs to get an average reading. So far everything seems to be working OK. Every once in a while it acts funny during turn on. Then I have to turn it off and start over. I will be happy to pay for the Arduino and shipping, just let me know how much.

Thanks
J

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