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vfd_driver [2016/01/27 09:41] – created kingkevinvfd_driver [2024/01/07 17:49] (current) – external edit 127.0.0.1
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 The firefly conductor is a vacuum fluorescent display (VFD) driver/controller. The firefly conductor is a vacuum fluorescent display (VFD) driver/controller.
  
-main parts:+{{:vfd_driver:setup.jpg?750|overall setup}} 
 + 
 +Main parts:
   * the VFD has been salvaged from a [[cash_register|Samsung SER6540II cash register]].   * the VFD has been salvaged from a [[cash_register|Samsung SER6540II cash register]].
-  * it came with Supertex HV518 VFD chips to drive the individual segments of the display.+  * it came with {{:vfd_driver:supertex_hv518.pdf|Supertex HV518}} VFD chips to drive the individual segments of the display.
   * I use a [[stm32f1xx|STM32F103]] micro-controller to control the display.   * I use a [[stm32f1xx|STM32F103]] micro-controller to control the display.
 +
 +===== setup =====
 +
 +{{  :vfd_driver:setup-details.jpg?400|detailed setup}}
 +Here are the parts used:
 +  - [[stm32f1xx#system_board|STM32F1 development board]], based on a [[http://www.st.com/web/catalog/mmc/FM141/SC1169/SS1031/LN1565/PF164476|STM32F103C8T6]] micro-controller (32-bit ARM Cortex M3, 72MHz)
 +  - the main VFD I salvaged from a [[cash_register|Samsung SER6540II cash register]] (cashier side)
 +  - the secondary VFD I salvaged from a [[cash_register|Samsung SER6540II cash register]] (customer side). this one is broken though.
 +  - main [[http://www.aliexpress.com/item/DP30V3A-Constant-Voltage-and-current-Step-down-Programmable-Power-Supply-module-buck-Voltage-converter-voltmeter-with/2021909507.html|power supply]]
 +  - adjustable [[http://www.aliexpress.com/item/120W-DC-DC-Boost-Converter-10-32V-to-36-60V-48V-54V-4A-Step-Up-Adjustable/1414029224.html|boost converter]] to drive the VFD
 +  - [[http://www.aliexpress.com/item/Free-shipping-10pcs-lot-4-channel-IIC-I2C-Logic-Level-Converter-Bi-Directional-Module-5V-to/32360153538.html|level shifter]] to connect the 3.3V STM32 signals to the 5V HV518 pins
 +  - [[http://www.aliexpress.com/item/FREE-SHIPPING-2PCS-LOT-CP2102-USB-2-0-to-UART-TTL-6PIN-Connector-Module-Serial-Converter/1095621364.html|USB to UART converter]] (SiLabs CP2102 based) to communicate with the micro-controller
 +  - [[http://www.aliexpress.com/item/Hot-Sale-1PCS-ST-LINK-Stlink-ST-Link-V2-Mini-STM8-STM32-Simulator-Download-Programmer-Programming/32343514985.html|SWD adapter]] (ST-Link v2 clone) to flash the micro-controller
 +  - USB to power (providing 5V), flash (using DFU), and communicate with (using CDC ACM) the micro-controller
 +
 +===== VFD =====
 +
 +==== introduction ====
 +
 +{{:vfd_driver:vfd1_front.jpg?0x250|main VFD front side}}
 +{{:vfd_driver:vfd1_back.jpg?0x250|main VFD back side}}
 +
 +{{:vfd_driver:vfd2_front.jpg?0x120|auxiliary VFD front side}}
 +{{:vfd_driver:vfd2_back.jpg?0x120|auxiliary VFD back side}}
 +
 +The SER6500 VFD comes with 3 {{:vfd_driver:supertex_hv518.pdf|Supertex HV518}} VFD drivers (2 are hidden behind the display).
 +
 +They each can driver 32 channels (up to 90V).
 +The VFD segments start already to be visible at 5V, but to get them bright you need higher voltages (I use 50V).
 +This is particularly important because you have to drive the digits and matrix one after each other.
 +If you do it fast enough, thanks to the persistence of vision they will not appear as flickering.
 +But because the segments are not on all the time, you need to drive them with higher voltage so on average they appear bright enough.
 +I drive the VFD with 60V and use a 100 Hz refresh rate.
 +
 +The VFD has 10 digits (7+3 segments) and 12 dot matrix (7x5 segments).
 +You would need 10*(7+3)+12*(5*7)=520 pins to drive each segment individuals.
 +That's far too many.
 +This is why they are multiplexed.
 +One pin drives the same segment across all digits (or matrix).
 +And you can select which digits/matrix you want to drive individuals.
 +Thus is you want to display different text on the digits/matrix, you first drive the grid for this digits/matrix (and only this), drive the segment for this character, and then you do the same for all others (one after each other).
 +That leaves us with 10+(7+3)+12+(5*5)=57 pins.
 +And this is also why 3 VFD drivers are need, because each can only control up to 32 channels.
 +
 +==== HV518 ====
 +
 +{{  :vfd_driver:hv518_diagram.svg?350|VFD interface pinout}}
 +Controlling them is pretty easy.
 +You just:
 +  * provide power (5V on the VDD pin)
 +  * send serial data into the built-in shift register (using the DIN and CLK pins)
 +  * latch to output the data in parallel (using the NLE pin)
 +  * enable the output buffers (using the STR pin)
 +  * this drives the 32 high voltage channels (with the voltage provided using the VPP pin)
 +The drivers also provide a DOUT pin which will relay the serial data.
 +This allows to chains them and shift the 3X32 data bits using a single line (the CLK pin is shared).
 +
 +==== pinout ====
 +
 +{{  :vfd_driver:vfd_pin.jpg?250|VFD interface pinout}}
 +The CN2 connector at the bottom of the SER6500 has the following pinout:
 +  - GND: ground
 +  - VDD: 5V to power the HV518 VFD driver
 +  - VPP: <90V to drive the VFD segments
 +  - DIN: to shift the data in
 +  - CLK: clock to shift the data, on the clock rise
 +  - #LE: enable latch on low (aka. negative LE, or NLE)
 +  - STR: strobe the shifted data
 +  - AUX: connected to ground when the auxiliary display is present
 +
 +{{  :vfd_driver:cn1_jumper.jpg?200|CN1 short}}
 +The CN1 connector at the top of the SER6500 is used to forward the signals to the auxiliary VFD (to display the price for the customer).
 +The second VFD has 10 digits, and is a copy of the 10 digits from the main VFD (minus comma and underline).
 +
 +The AUX pin of CN2 is shorted to ground when the auxiliary VFD is connected.
 +You can use the AUX pin to detect if the auxiliary VFD is present by pulling the pin up and checking if it's low (because shorted to ground).
 +You can also the use AUX pin as second ground pin (i.e. for the VPP power suply).
 +If the auxiliary VFD is not present, just short the 3rd right-most top pin with the 2nd right-most bottom pin.
 +
 +==== segments ====
 +
 +The three HV518 are chained.
 +To control all the VFD segments you just have to shift 3x32 bits.
 +
 +In the following tables the left-most 32-bit word is transmitted first, with least significant bit (right-most) shift first.
 +
 +{{  :vfd_driver:vfd_grid.jpg?400|VFD grids}}
 +grid selection (for digits and dot matrix)
 +^ hex value (3x32 bits) ^ word ^ bit ^ display type ^ grid position ^
 +| 00000000 00000008 00000000 | 2 | 4 | matrix | 1 |
 +| 00000000 00000004 00000000 | 2 | 3 | matrix | 2 |
 +| 00000000 00000002 00000000 | 2 | 2 | matrix | 3 |
 +| 00000000 00000001 00000000 | 2 | 1 | matrix | 4 |
 +| 80000000 00000000 00000000 | 1 | 32 | matrix | 5 |
 +| 40000000 00000000 00000000 | 1 | 31 | matrix | 6 |
 +| 20000000 00000000 00000000 | 1 | 30 | matrix | 7 |
 +| 10000000 00000000 00000000 | 1 | 29 | matrix | 8 |
 +| 08000000 00000000 00000000 | 1 | 28 | matrix | 9 |
 +| 04000000 00000000 00000000 | 1 | 27 | matrix | 10 |
 +| 02000000 00000000 00000000 | 1 | 26 | matrix | 11 |
 +| 01000000 00000000 00000000 | 1 | 25 | matrix | 12 |
 +| 00000000 00002000 00000000 | 2 | 14 | digit | 1 |
 +| 00000000 00001000 00000000 | 2 | 13 | digit | 2 |
 +| 00000000 00000800 00000000 | 2 | 12 | digit | 3 |
 +| 00000000 00000400 00000000 | 2 | 11 | digit | 4 |
 +| 00000000 00000200 00000000 | 2 | 10 | digit | 5 |
 +| 00000000 00000100 00000000 | 2 | 8 | digit | 6 |
 +| 00000000 00000080 00000000 | 2 | 8 | digit | 7 |
 +| 00000000 00000040 00000000 | 2 | 7 | digit | 8 |
 +| 00000000 00000020 00000000 | 2 | 6 | digit | 9 |
 +| 00000000 00000010 00000000 | 2 | 5 | digit | 10 |
 +
 +{{  :vfd_driver:vfd_digit.jpg?150|digit segments}}
 +grid selection (for digits and dot matrix)
 +^ hex value (3x32 bits) ^ word ^ bit ^ segment ^
 +| 00000000 00004000 00000000 | 2 | 15 | underline |
 +| 00000000 00008000 00000000 | 2 | 16 | dot |
 +| 00000000 00010000 00000000 | 2 | 17 | comma |
 +| 00000000 00020000 00000000 | 2 | 18 | a |
 +| 00000000 00040000 00000000 | 2 | 19 | b |
 +| 00000000 00080000 00000000 | 2 | 20 | c |
 +| 00000000 00100000 00000000 | 2 | 21 | d |
 +| 00000000 00200000 00000000 | 2 | 22 | e |
 +| 00000000 00400000 00000000 | 2 | 23 | f |
 +| 00000000 00800000 00000000 | 2 | 24 | g |
 +
 +{{  :vfd_driver:vfd_matrix.jpg?150|dot matrix segments}}
 +grid selection (for digits and dot matrix)
 +^ hex value (3x32 bits) ^ word ^ bit ^ column ^ row ^
 +| 00000000 01000000 00000000 | 2 | 25| 1 | 1 |
 +| 00000000 02000000 00000000 | 2 | 26 | 1 | 2 |
 +| 00000000 04000000 00000000 | 2 | 27 | 1 | 3 |
 +| 00000000 08000000 00000000 | 2 | 28 | 1 | 4 |
 +| 00000000 10000000 00000000 | 2 | 29 | 1 | 5 |
 +| 00000000 20000000 00000000 | 2 | 30 | 1 | 6 |
 +| 00000000 40000000 00000000 | 2 | 31 | 1 | 7 |
 +| 00000000 00000000 00000001 | 3 | 1 | 2 | 1 |
 +| 00000000 00000000 00000002 | 3 | 2 | 2 | 2 |
 +| 00000000 00000000 00000004 | 3 | 3 | 2 | 3 |
 +| 00000000 00000000 00000008 | 3 | 4 | 2 | 4 |
 +| 00000000 00000000 00000010 | 3 | 5 | 2 | 5 |
 +| 00000000 00000000 00000020 | 3 | 6 | 2 | 6 |
 +| 00000000 00000000 00000070 | 3 | 7 | 2 | 7 |
 +| 00000000 00000000 00000100 | 3 | 9 | 3 | 1 |
 +| 00000000 00000000 00000200 | 3 | 10 | 3 | 2 |
 +| 00000000 00000000 00000400 | 3 | 11 | 3 | 3 |
 +| 00000000 00000000 00000800 | 3 | 12 | 3 | 4 |
 +| 00000000 00000000 00001000 | 3 | 13 | 3 | 5 |
 +| 00000000 00000000 00002000 | 3 | 14 | 3 | 6 |
 +| 00000000 00000000 00004000 | 3 | 15 | 3 | 7 |
 +| 00000000 00000000 00010000 | 3 | 17 | 4 | 1 |
 +| 00000000 00000000 00020000 | 3 | 18 | 4 | 2 |
 +| 00000000 00000000 00040000 | 3 | 19 | 4 | 3 |
 +| 00000000 00000000 00080000 | 3 | 20 | 4 | 4 |
 +| 00000000 00000000 00100000 | 3 | 21 | 4 | 5 |
 +| 00000000 00000000 00200000 | 3 | 22 | 4 | 6 |
 +| 00000000 00000000 00400000 | 3 | 23 | 4 | 7 |
 +| 00000000 00000000 01000000 | 3 | 25 | 5 | 1 |
 +| 00000000 00000000 02000000 | 3 | 26 | 5 | 2 |
 +| 00000000 00000000 04000000 | 3 | 27 | 5 | 3 |
 +| 00000000 00000000 08000000 | 3 | 28 | 5 | 4 |
 +| 00000000 00000000 10000000 | 3 | 29 | 5 | 5 |
 +| 00000000 00000000 20000000 | 3 | 30 | 5 | 6 |
 +| 00000000 00000000 40000000 | 3 | 31 | 5 | 7 |
 +
 +===== micro-controller =====
 +
 +The hardware used to control this VFD is a [[stm32f1xx#system_board|STM32F1 development board]], based on a [[http://www.st.com/web/catalog/mmc/FM141/SC1169/SS1031/LN1565/PF164476|STM32F103C8T6]] micro-controller (32-bit ARM Cortex M3, 72MHz).
 +
 +The firmware is available [[https://git.cuvoodoo.info/firefly_condcutor|here]].
 +It :
 +  * starts by testing all segments of the VFD
 +  * plays an animation
 +  * and finally displays the text typed in over the USB CDC ACM or USART1 ports
 +
 +The data is shifted out from the micro-controller to the drivers using SPI (this protocol fits well what the HV518 requires).
 +A timer will periodically refresh all parts of the VFD at 100 Hz.
 +
 +Since the STM32 provides only 3.3V I/Os and the HV518 requires 5V signals I used a simple [[http://www.aliexpress.com/item/Free-shipping-10pcs-lot-4-channel-IIC-I2C-Logic-Level-Converter-Bi-Directional-Module-5V-to/32360153538.html|level shifter]].
 +But actually it works fine also without, by directly connecting the HV518 to the STM32.
 +
 +Connection:
 +^ STM32 signal ^ board pin ^ VFD CN2 pin ^ HV518 signal ^
 +| | GND | 1 | GND |
 +| | 5V | 2| VDD |
 +| | | 3 | VPP |
 +| SPI1_MOSI | PA7 | 4 | DIN |
 +| SPI1_SCK | PA5 | 5 | CLK |
 +| GPIO | PA4 | 6 | NLE |
 +| GPIO | PA6 | 7 | STR |
 +| | | 8 | AUX |
 +
 +The VPP and GND pins to drive the VFD segments are provided using an external power supply.
 +I use a [[http://www.aliexpress.com/item/120W-DC-DC-Boost-Converter-10-32V-to-36-60V-48V-54V-4A-Step-Up-Adjustable/1414029224.html|boost converter]] and set it to 50V.
vfd_driver.1453887684.txt.gz · Last modified: 2024/01/07 17:49 (external edit)