For doing testing on PIC circuits that are under development, I often send out a little data stream on any available i/o line. First I send out a pulse that goes high for some relatively short time. This pulse is used simply to initially trigger the scope. I then send out a low for a time equal to the trigger pulse. Then I begin sending out 8 data bits (I usually make the data bits 1 ms wide, simply because I almost always have a 1 ms timer routine in all my programs. But make it whatever width you find convenient.) I then ensure that after the eighth data bit I send out a low for enough time to allow the scope trace to disappear from the screen, ready for the next trigger. I then do this over and over again at regular intervals. When done often enough, the scope display will appear stationary and it is very easy to determine the value of each bit. I adjust my scope so that each data bit occupies one major grid unit. I can now read off any binary value from 0 to 255. You are not limited to 8 bit values. I routinely display 16 bit and even 24 bit values this way. For those who don't own a scope, you can use a shift register or set of shift registers to cause the binary values to be displayed on LEDs. When doing this, I use different colors for each group of 8 data bits. In a pinch you can get by with just a clock and a data line. This means you have to tie the other shift register control lines to a high or low, and you will get flicker as the data is clocked through, but if you clock fast and then display for a much longer period, the result is not too bad. Remember, this is just a test aid. It is often useful to have such test aids built on little PC boards or perf boards, with color coded hook leads attached so you can attach to +5, Gnd, a Clock and a Data line. Anyone else have any little debugging/testing aids they would like to share? One of the most versatile aids I use is an LCD module that I have hooked up to a proto board that has a PIC on it programmed to accept input at 4800 baud normal or inverted (jumper selectable). It also has a two wire serial interface consisting of a Clock and Data line for those times when I don't have a uart or uart routine on the host. The same board also has a 4800 baud output in both normal and inverted form that sends out a simple test message. A dip switch can also select an echo mode so it sends out whatever byte it last received. The data received can be displayed as ASCII text, or it can be formatted as either hex or binary, or interpreted as 8/16/24/or 32 bitnumerical data and displayed in base ten. The on board RAM forms a circular buffer and you can review the last 64 data items. A start/stop switch allows you to control whether or not new input is placed in the circular buffer. A set of analog inputs allows you to measure several ground referenced voltages, including the +5 of the circuit it is attached to. A 4x4 keypad is used to menu select what is displayed and what functions are in effect. I am always looking for ways to improve this tool. It makes for a wonderful PIC project. One of these days I will make a PC board for it... if I ever stop adding features! Fr. Thomas McGahee ----- Original Message ----- From: "M. Adam Davis" To: Sent: Thursday, March 28, 2002 3:52 PM Subject: Re: [PIC]: Simplest, cheapest, easiest solution for displaying 2 numbers. > The cheapest visual solution is one very cheap LED. Like the old engine > indicators: > > Blink the number of times for the first digit (1/4 second on, 3/4 second > off) > Pause for 2 seconds > Blink the number of times for the second digit (1/4 second on, 3/4 > second off) > Pause for 5 seconds > > Takes 25 seconds max to read the two digits off the display, but costs > less than a few cents, and only needs one line. > > I bet there's even a way to do it with zero dedicated lines. > > -Adam > > Drew Vassallo wrote: > > > I want to display just 2 numbers out of the PIC somehow. Doesn't matter > > how, just the simplest, easiest, cheapest solution. Could be an LED > > display, LCD, smoke signals, it doesn't matter. > > > > I'd like to use a 12C67x series 8-pin PIC, though, so I only have 3 > > lines to > > use maximum. If it's not possible in this case, I would have to move > > to a > > larger chip, but it's not preferred to do this. > > > > I have a 2-wire LCD interface already working, but I'd like to make it > > simpler/cheaper if possible. > > > > Any suggestions? > > > > --Andrew > > > > _________________________________________________________________ > > Chat with friends online, try MSN Messenger: http://messenger.msn.com > > > > -- > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > > > > > > > > > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads