Vacuum fluorescent display with integrated driver - Page 1
Forum section: electronics / projects

author: Bendba
author_rank: Regular Contributor
timestamp: January 09, 2018, 12:53:43 pm
content: Hi,I found something quite interesting on eBay (https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com.au%2Fulk%2Fitm%2F252881931726)Those as quite obviously dvd player's front panel circuit boards. Even just for the brand new VFD panel, $1 a piece is pretty good, so I bought the lot (74 of them)The nice thing is that the board is driven by an ATMega microcontroller (ATMega 8535L), hopefully not write protected so I can flash them with my own software. Otherwise, I'll just replace the chip.It also has a real time clock, a CR2032 cell holder, an IR receiver, a couple of LED's and 7 push buttons, and the driver for the filaments, so quite versatile. Just takes one 5V and one 12V supplies.The strange/interesting thing is the VFD panel itself (HCV-03SM06T), they have an integrated driver and only 13 pins. If anyone has any idea what to pinout/protocol is, that would be extremely helpful.2 pins for one side of the filaments,2 pins for the other side of the filaments,2 pins for ground,1 pin for 12V dc supply of the panelSo I'm left with 6 pins for communication.I'll hook one up to a logic analyzer tomorrow to see if I can work it out but the board by itself only displays three different things, a power symbol, or the word "WAIT" or the time, any other display would need the rest of the dvd player to be present. So, not much to work from.Any ideas anyone?ThanksEdit:Out of the 6 pins left, one seems to have something to do with the filament driving (the track inside the panel's glass is fairly thick so probably to do with supply, not data)

author: FireBird
author_rank: Regular Contributor
timestamp: January 09, 2018, 01:28:53 pm
content: These front panels are used in Topfield PVRs. While I’m not sure if I have the pinout of the VFD itself, the connector and the communication protocol with the mainboard has been reversed and is documented somewhere. So in theory you could use the panel as is (display, RTC, IR receiver, buttons and LEDs). I just need to dig the stuff out. The ATMega is not write protected – at least it wasn’t in the past.

author: Bendba
author_rank: Regular Contributor
timestamp: January 09, 2018, 07:53:38 pm
content: That would be absolutely awesome.

author: james_s
author_rank: Super Contributor
timestamp: January 09, 2018, 08:15:42 pm
content: I've seen some similar Chip-On-Glass VFDs, it's probably a custom display but if you can find a datasheet for something similar that ought to get you close. Alternately since you have the entire board to drive it you should be able to reverse engineer it fairly easily, many VFD drivers are simply shift registers.

author: FireBird
author_rank: Regular Contributor
timestamp: January 09, 2018, 09:55:07 pm
content: Here are some details. As I only know the front panels from European Toppys, there might be slight differences in your version.ConnectorsCode:1 Black - 5V Standby2 Brown - TxD (Frontpanel -> Mainboard)3 Red - RxD4 Orange - GND5 Yellow - P/S6 Green - Switch1*7 Blue - Switch28 Violet - Switch3*9 Gray - GND10 White - +17V11 Pink - Switch412 lt Blue - Switch513 Black - NC14 Brown - NCThe front panel uses the Switch outputs to power sequence different parts of the Topfield (mainboard, HDD, tuner,...). The P/S output is used to shut down the power supply. In this low power mode, only the 5V standby is provided and all other voltages including the +17V are gone.J1 is used to read or write the Atmel:1 = MISO2 = 5V3 = SCK4 = MOSI5 = RESET*6 = GNDSeen from top:123456Front panel commandsThe communications is performed with 5V 19200,n,8,1 and has the following format (both directions):<STX> <cmd>  <ETX>The lower nibble of CMD reflects the number of parameter bytes. To perform a first test, here are some simple commands. Whenever you press one of the buttons (except power), the front panel should send:<STX> <51> <key code> <ETX>The VFD doesn’t have a character generator and therefore you have to send a 48 byte bitmap to address all segments. This segment data is broken up into 6 0x99 commands. The first parameter is the address of the bitmap buffer, the following 8 bytes are the bitmap.Code:<STX> <99> <00> <c0> <0e> <0c> <78> <31> <61> <c2> <08> <ETX><STX> <99> <08> <02> <00> <00> <00> <00> <00> <00> <00> <ETX><STX> <99> <10> <3c> <00> <00> <00> <00> <00> <00> <00> <ETX><STX> <99> <18> <00> <00> <00> <04> <20> <f0> <00> <00> <ETX><STX> <99> <20> <03> <c1> <40> <fd> <40> <00> <d0> <eb> <ETX><STX> <99> <28> <00> <00> <00> <00> <00> <00> <00> <00> <ETX>You can also use the 0x91 command to turn all segments on or off:<STX> <91> <Data> <ETX>Data = 00 or FFIRThe ATMega decodes the NEC IR format.Hope this helps. If you can make the front panels work and would like to use the whole module, I can create a document with all the commands I’m aware of.Cheers,Alex

author: james_s
author_rank: Super Contributor
timestamp: January 09, 2018, 10:03:01 pm
content: That certainly suggests that the integrated display driver is nothing more than a shift register with HV outputs, it probably has a clock, data, latch and output enable inputs.

author: Gyro
author_rank: Super Contributor
timestamp: January 09, 2018, 10:20:47 pm
content: Firebird as in Toppy TAPs Firebird?My TF5800 is still going strong with several of your TAPs installed (thank you).

author: FireBird
author_rank: Regular Contributor
timestamp: January 09, 2018, 10:23:13 pm
content: Yep, you're welcome.

author: Bendba
author_rank: Regular Contributor
timestamp: January 11, 2018, 01:02:24 am
content: Spot on.That is awesome!I connected the logic analyzer to it, serial is as you've said, when pressing buttons, I get 00,02,51,<button number>,03I'll connect a serial interface and start sending some strings to see what I can get out of it.If you have a list of commands, that would be amazing.Thanks a lot!Quote from: james_s on January 09, 2018, 10:03:01 pmIt looks like it indeed. As soon as I can display more then the "wait", time and on symbol, I'll try to work it what the sequence is.Confirm the first rule of reverse engineering once again:Always check if someone already did it.

author: FireBird
author_rank: Regular Contributor
timestamp: January 11, 2018, 04:30:22 pm
content: Thisshould provide enough details for some hours of playing around.If something doesn’t work, please be reminded that this is rather old info and that not all commands will be implemented in your front panel model. And I'm sure that the pdf will contain some errors. Have fun.

author: Bendba
author_rank: Regular Contributor
timestamp: January 11, 2018, 08:44:52 pm
content: Awesome, thanks for that. The mapping of the segments is even already doneIf there is any difference, I'll make an updated copy.I'll also try to work out the signal controlling the VFD panel itself so I can reprogram the ATMega if I decide to.But I don't think I will.I expected to find a few unused pins, so I could add some sensor to it but all the ADC's are already connected (even though most as used as digital output) there is only a couple of digital pins that are not really used as they are connected to the 5 switch lines on the cable.It would be much easier to program a desperate controller and just send commands to the display board.