SX28 Chip Based Handheld

Green Phantom

Remember when back in January 19, 2008 (1/19/2008) I posted a topic about using HCMS-29XX serial 8-digit dot-matrix LED displays for a handheld "computer?"

I had been very carefully studying the data sheets at Avago and just now, this weekend, I tested one of two of the HCMS-291X displays; one red (HCMS-2912) and one green (HCMS-2913.)· It was very tricky to program with the SX microcontroller because there were new considerations for the connections to the SX which I discovered at the 11th hour.· I couldn't simply leave the LED display's pin #15, RS, tied to ground.· After reviewing the Avago data sheets, I discovered that I was required to program the device's light intensity for both the left digits and right digits.· Just last night, I had trouble with the negative-edged RESET pin (#24) on the HCMS display device as well as for the RS pin.· When I finally got the display lighting up, there was still a problem.· Only half the display lit up!

Again, nonetheless, after reviewing the manuals, I found out that out of the factory the LED displays were pre-programmed in "SLEEP" mode and I was required to edit my L6015XXX program in SX/B to shoehorn in a code to SLEEP the device and then turn on both banks of four digits of dot-matrix display.· The 2KB of ROM available in the SX28 virtually maxed out by the time I perfected the L6015 device program.· All I have left to do now is to make some final adjustments for more reliable tact switch keypad entry and I had carved out a 13-button numeric/function keyboard enclosure, one of the smaller beige project boxes from Radio Shack.

According to the data sheets, you need to enter one SLEEP instruction byte and two display brightness instruction bytes; one for the left characters, one for the right characters on the display.· You also should program the SX to send an 0 and 1 in sequence from the SX to the HCMS display RESET pin.· To initialize the display, a 1 is sent from the SX to the HCMS display pin RS (#15), followed by the three initializing instruction bytes described above.· Then RS is set to 0, where normal operation of the display is performed, to display the characters.

To accommodate the custom character set into the available ROM in the SX28, I had to design a unique character display font based around the 7-segment LED display.· I designed a hexadecimal-oriented ASCII character map that starts at 0 to 9 and the rest of the alpha-numeric characters and symbols start at A to Z.· I invented a programming language for the handheld device itself.· Originally I designed a 64-character custom font with readable alpha-numberic characters.· But this human-readable 64-character set requires far more work to make them readable through the display (in interpretation of hex characters and text formats)· With the "program language" in place, it wouldn't fit inside the ROM without sacrificing some of the features.· So· I took inspiration from Coleco handheld electronic football game consoles under malfunction by a bad battery and established the custom character map built around otherwise erratic symbols in a 7-segment display.· A 7-segment display can display the Greek letter mu (a backwards number 4) and I adapted it as the letter "M."· I use an upside-down "A" in 7-segment format and use it as a "W."

But I have other uses for the 64-character, human-readable, alphanumeric set.· I could make a kind of texting device with which you would send and receive, for example, a 32-character text message; a sort of TTD device as if for the deaf.

But finally, the LED display lights up!· I just took a few photos of the display in action while my little handheld, old-school computer remains under construction.

I call the device a "PhanCOM."

I hope you like it...

Green Phantom


Post Edited (Green Phantom) : 8/15/2009 9:38:14 PM GMT

CounterRotatingProps

Hello Mr. Phantom

I love stuff like this!

Keep at it.

cheers,

Howard

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No matter how much you push the envelope, it'll still be stationery.

Green Phantom

I appreciate that, Howard!

Unfortunately, a few days ago, I had to redo the custom circuit board from scratch because the individual board for the LED display couldn't fit over the main board containing the SX28 microcontroller. It almost worked when I powered up the new device but the red HCMS-2912 display gave trouble, mainly due to the poor fit of the board to the enclosure. I must have accidentally bent one of the display pins and put the LEDs out of commission. So I ordered a spare display, albeit an HCMS-2972, for bigger LEDs. I am still considering desoldering the display from the board it originally was placed into and test it on the SX Tech Board. It might still be good. But I ordered the new display anyway, in case something happened.

I rebuilt the custom circuit board, now with the display and piezo speaker fully integrated with the circuit board. Just now, I ordered a 30-pin SIP wire-wrap-type circuit board component socket array which I will use to relocate the display in its new socket. The socket pins are adjusted on the board so that the display can fit behind the plastic display cutout and after soldering the SIP socket array I cut the bottom ends so the board fits in the enclosure.

The 6015 uses a 7805 regulator and is powered by a 9-volt battery. I even shoehorned in wireless communication into it! Using SERIN and SEROUT in SX/B, it sends and receives data at 2400 baud, inverted through a 433.92MHz ASK radio-frequency transmitter-receiver pair. Reason: there is no room for EEPROM circuitry to "load" programs for it. I will need to program a separate SX28 chip to contain pre-designed programs, 80 bytes each. One of the applications I propose is robotics, to send 80 bytes of data from the 6015 to a robot equipped with the RF/ASK trasmitter/recieiver modules. Other applications may include Dungeons & Dragons electronic dice rolls, chronometer, 2-way silent "texting" communication and a few games of chance.

One example of chronometer work can involve a "Hot Wheels" die-cast model car racetrack with two lanes and a digital finish line; left lane red and right lane green for LEDs and a pair of lever switches, one for each lane. When either car hits the switches, the racetrack electronic circuitry will send a signal to the 6015 which will first stop the 10-second timer on the car that made it first and then the 10-second clock for the other lane stops when the car in that other lane hits the switch, to give an example of an application.

How did you like the keypad enclosure overlay half carved out? And the grille for the piezo speaker? While the symbols in the display in one of the pictures are odd, there is a sample of the possibilities. Use your imagination!

Thanks for your reply!

Green Phantom

CounterRotatingProps

>· will need to program a separate SX28 chip to contain pre-designed programs, 80 bytes each

Neat what you can pack into such a small space, eh?

The 2400 baud radio technique sounds useful for many things.· When you get time, please tell us more about that.

Are the pair of clippers in the photo normal, fingernail sized?·· What's PhanCom's actual dimensions?
I like to take old remotes from TV's, stereo's, and VCR's and convert them into· " FrankenTrolls "·
And my first robot was made out of a cardboard shoebox [noparse][[/noparse]:=)

cheers,
Howard

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
No matter how much you push the envelope, it'll still be stationery.

Green Phantom

The dimensions are 2.5 inches across by 4.5 long by little over an inch deep. The package is an old Radio-Shack beige project enclosure. I deleted the old pics in my post and submitted a trio of new ones with the hand-held now fully functional. Only the button caps are missing and I am looking for ways to make them. The communications devices inside the box may not be working due to a lack of testing but it gave me another challenge to give the project a new package so that all components in it are set more comfortably. On a different project enclosure, I plan to rebuild this device from scratch with one single circuit board rather than two. Yes, I will need to program a separate SX micro controller for the programs to upload into the PhanCOM via the Wen Shing transmitter device on another project box, but this is not yet really important. Now I have to come up with a package that can accommodate all components more comfortably. I will later test the wireless remote devices in the system. I also have in the works a bigger version of this PhanCOM. It is the same thing, but built in a project lab filip-up box made from the outer enclosure from a Century jump-starter battery pack. It already has a breadboard built into it but I need to redo the keypad on the left side of it and build separate circuit boards, the main PhanCOM SX28 micro-contorller board and the others for various applications. I cannot guarantee beyond what I have accomplished so far, as shown in the pics but hopefully I'll get there.

Green Phantom

Green Phantom

Just now, I discovered that my PhanCOM will need a really long-lasting battery because standard 9Vs are sucked dry if you are not careful. But battery sucking is nothing new and my PhanCOM isn't the first device that sucks batteries like Dracula. You know those hand-held video arcades packaged inside a joystick, including Jakks MsPac Man, Namco and Super Pac-Man built-in-joystick consoles? You will drain out four AA alkaline batteries within days - not weeks. Happily, though, the 9V battery lasted long enough so that I could demonstrate my project to a dedicated Radio Shack store manager. Boy she is one motherly bottle of wine! My PhantAsm programming language I built-in into the SX28 chip ran smooth, except for a couple of adjustments for memory address jumping and branching I had to take care of. It put the speaker to sound beautifully. My PhanCOM worked beautifully! There is one issue concerning data reading (like those early IBM PC "debug.com" files on disk.) When reading RAM as "text," the SX28 jumps two bytes before displaying the data in RAM whenever I press the lower right button and 7, select the address in RAM and then the lower-right button again and 3. To read RAM starting at address $58H, for example, I have to select address $56H. There wasn't enough room in the SX28 ROM to fix that problem so I had to leave it as-is. Originally, I set the internal oscillator to 128KHz but when I discovered that the speaker emitted much too low pitches at maximum speed of the program execution, I decided to speed up the SX28 back to its maximum internal clock speed of 4MHz - and modify the PAUSE XXX commands in SX/B with it. Is anybody interested in the schematics for my project and the SX/B source code? Meanwhile I will write a book about how to program the PhanCOM with my recently developed PhantAsm language.

Green Phantom