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qmk_firmware/keyboards/fc660c/README.md

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FC660C Alt Controller

This file and the entire QMK port of this board are based on its TMK implementation: https://github.com/tmk/tmk_keyboard/tree/master/keyboard/fc980c

Make example for this keyboard (after setting up your build environment):

make fc660c:default

See build environment setup then the make instructions for more information.

To flash the firmware, press the reset button on the controller and run:

sudo make fc660c:default:dfu

Thread on Geekhack: https://geekhack.org/index.php?topic=88439.0

Also: https://geekhack.org/index.php?topic=88720.0

Pinouts

|Switch  |Controller |
|  board |     board |Description                           |Schematic  |ATmega32u4
|--------|-----------|--------------------------------------|-----------|------------
| 1      |20         | FG                                   |FG         |GND
| 2      |19         | GND                                  |GND        |GND
| 3      |18         | GND                                  |GND        |GND
| 4      |17         | 3.3V                                 |V33        |3.3V/5V
| 5      |16         | 5V                                   |Vcc        |5V
| 6      |15         |*Z6-TP1684-4-HYS(o)                   |FBSTB      |PC7
| 7      |14         |*Z6-TP1684-2-KEY(i)                   |OUT        |PC6
| 8      |13         |*Z2-AD5258-5-SCL(I2C)                 |SCL        |PD0(TWI)
| 9      |12         |*Z2-AD5258-4-SDA(I2C)                 |SDA        |PD1(TWI)
|10      |11         |*Z4-LV4051A-6-~EN(Col 0-7)            |INH_1      |PB4
|11      |10         |*Z5-LV4051A-6-~EN(Col 8-F)            |INH_2      |PB3
|12      | 9         |+Z7-LV07A-5 (LV4051A-9-C)             |SEL_C      |PB2
|13      | 8         |+Z7-LV07A-1 (LV4051A-10-B)            |SEL_B      |PB1
|14      | 7         |+Z7-LV07A-3 (LV4051A-11-A)            |SEL_A      |PB0
|15      | 6         |+Z3-LVC138A-3-C                       |COL4       |PD6
|16      | 5         |+Z3-LVC138A-2-B                       |COL3       |PD5
|17      | 4         |+Z3-LVC138A-1-A                       |COL2       |PD4
|18      | 3         |+Z3-LVC138A-4-~G2A  Z6-TP1684-5-~EN   |COL1       |PD7
|19      | 2         |+Z7-LV07A-11-~InsertLED               |LED1       |PB5
|20      | 1         |+Z7-LV07A-13-~CapsLED                 |LED2       |PB6

* 5V intferface
+ 3.3V interface

Key Matrix

Row5-7 have no key, you can omit scaning on those lines. Topre original controller scans those rows for some reason.

|    |0   |1   |2   |3   |4   |5   |6   |7   |8   |9   |A   |B   |C   |D   |E   |F   |
|----|----|----|----|----|----|----|----|----|----|----|----|----|----|----|----|----|
|   0|Q   |W   |E   |Tab |R   |U   |T   |Y   |O   |P   |[   |I   |]   |    |\   |Del |
|   1|1   |2   |3   |Esc |4   |7   |5   |6   |9   |0   |-   |8   |=   |    |BSpc|Ins |
|   2|    |LWin|LAlt|LCtl|    |    |    |Spc |RAlt|    |RCtl|    |Fn  |Down|Left|Rght|
|   3|    |Z   |X   |LSft|C   |N   |V   |B   |,   |.   |/   |M   |RSft|Up  |    |    |
|   4|A   |S   |D   |Caps|F   |J   |G   |H   |L   |;   |'   |K   |    |    |Entr|    |
|   5|    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |
|   6|    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |
|   7|    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |    |

Logic analyzer pics:

This code emuluates what original cotnroller does for matrix scan.

Row designation

LV138A(Z3) selects a row line and gives strobe by enabling with ~G2A(18).

|Row |A/17|B/16|C/15|
|----|----|----|----|
|0   |0   |0   |0   |
|1   |1   |0   |0   |
|2   |0   |1   |0   |
|3   |1   |1   |0   |
|4   |0   |0   |1   |
|5   |1   |0   |1   |
|6   |0   |1   |1   |
|7   |1   |1   |1   |

Column designation

LV4051A(Z4, Z5) select one of 16 column lines to sense capacitance of switches.

|Col |A/14|B/13|C/12|Z4-EN/10|Z5-EN/11|
|----|----|----|----|--------|--------|
|0   |0   |0   |0   |0       |1       |
|1   |1   |0   |0   |0       |1       |
|2   |0   |1   |0   |0       |1       |
|3   |1   |1   |0   |0       |1       |
|4   |0   |0   |1   |0       |1       |
|5   |1   |0   |1   |0       |1       |
|6   |0   |1   |1   |0       |1       |
|7   |1   |1   |1   |0       |1       |
|8   |0   |0   |0   |1       |0       |
|9   |1   |0   |0   |1       |0       |
|A   |0   |1   |0   |1       |0       |
|B   |1   |1   |0   |1       |0       |
|C   |0   |0   |1   |1       |0       |
|D   |1   |0   |1   |1       |0       |
|E   |0   |1   |1   |1       |0       |
|F   |1   |1   |1   |1       |0       |

FCC documents

https://fccid.io/RPKFC660C

Datasheets

3.3V power supply

LV07A and LVC138A are 5V-tolerant and can be powered with 5V, the keyboard will work only with 5V power supply. It may not be completely safe to operate LV138A with 5V Vcc, its datasheet says:

Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

Digipot AD5258

Controller can operate AD5258 via I2C to change actuation point of keys. This may make keyboard unusable accidentally and it will be difficult to recovery in some situation. For safety firmware doesn't support it at this point, though.

Lower value of RDAC register causes shallower actuation point.

Resources