Hardware - padraigfl/awesome-arcade-coder GitHub Wiki

This page covers details around how the hardware itself operates; please add details relating to the specific components, optimal timings and how the hardware operates here.

TODO:

circuit diagrams: you can find KiCad sketches available at https://github.com/ColdFerrin/twsu-arcade-coder-pcb
details on specifics for optimisations (e.g. brightness control, how many buttons can be pressed at once)
a full breakdown of the input tracking process: @jake-walker has some great work done on this for single button input tracking at https://jake-walker.github.io/rs-arcade-coder/hardware/buttons/
how to connect to a computer (see this page for some details currently

Features

144 RGB individually addressable LEDs
144 membrane buttons
Accelerometer
ESP32-WROOM-32D microcontroller (capable of bluetooth and wifi; if you don't know this microcontroller it's worth looking up what it can do)
1 digital button
2 rear status LEDs
LiPo battery (charged via USB-C port)

Components

1x ESP32-WROOM-32D
9x 74HC595 Shift Registers: for controlling LEDs
1x ICN2012 (similar to 74LS138) for multiplexing LED channels and processing membrane button inputs
1x SC7A20 Accelerometer

Button/LED groupings

Only 24 buttons / RGB LEDs can be controlled at a time, via multiplexing across 6 channels we are able to track the full range of buttons and LEDs. The groupings of both are the same and consist of 0+n -> 0+n+12 and 60+n -> 60+n+12 where n is one of [0, 12, 24, 36, 48, 60]

Here is a rough approximation of the board layout following a format of ChannelNum_RGBNum (e.g. 2_13 will refer to the 2nd LED/button on the second row of the 3rd channel):

O	0_00	0_01	0_02	0_03	0_04	0_05	0_06	0_07	0_08	0_09	0_10	0_11	X
	1_00	1_01	1_02	1_03	1_04	1_05	1_06	1_07	1_08	1_09	1_10	1_11
	2_00	2_01	2_02	2_03	2_04	2_05	2_06	2_07	2_08	2_09	2_10	2_11
	3_00	3_01	3_02	3_03	3_04	3_05	3_06	3_07	3_08	3_09	3_10	3_11
	4_00	4_01	4_02	4_03	4_04	4_05	4_06	4_07	4_08	4_09	4_10	4_11
	5_00	5_01	5_02	5_03	5_04	5_05	5_06	5_07	5_08	5_09	5_10	5_11
	0_12	0_13	0_14	0_15	0_16	0_17	0_18	0_19	0_20	0_21	0_22	0_23
	1_12	1_13	1_14	1_15	1_16	1_17	1_18	1_19	1_20	1_21	1_22	1_23
	2_12	2_13	2_14	2_15	2_16	2_17	2_18	2_19	2_20	2_21	2_22	2_23
	3_12	3_13	3_14	3_15	3_16	3_17	3_18	3_19	3_20	3_21	3_22	3_23
	4_12	4_13	4_14	4_15	4_16	4_17	4_18	4_19	4_20	4_21	4_22	4_23
	5_12	5_13	5_14	5_15	5_16	5_17	5_18	5_19	5_20	5_21	5_22	5_23
						Home Button

ESP32 Pinout

GPIO	Component / Function
0	exposed, required for bootloader mode
1	UART TX
2	Home button
3	UART RX
4	HC595 OE
5	HC595 Data
16	HC595 Latch
17	HC595 Clock
18	ICN2012 A1
19	ICN2012 A0
21	ICN2012 A2
22	LED1
23	LED2
25	Unknown (possibly battery)
26	SC7A20: SDA
27	SC7A20: SCL
32	Analog button data for rows 6 and 12
33	Analog button data for rows 5 and 11
34	Analog button data for rows 4 and 10
35	Analog button data for rows 3 and 9
36	Analog button data for rows 2 and 8
39	Analog button data for rows 1 and 7

LEDs 12-15 appear to be unused so could be utilised if you want to add extra functionality. Pins 26 and 27 could be used for multiple i2c devices as well.

LED rendering

LED data is passed in in batches of 9 bytes at a time for each multiplexed channel. The data is passed into the daisy chained shift registers in the following format:

$${\color{green}G11}$$	$${\color{green}G10}$$	$${\color{green}G09}$$	$${\color{green}G08}$$	$${\color{green}G07}$$	$${\color{green}G06}$$	$${\color{green}G05}$$	$${\color{green}G04}$$
$${\color{red}R11}$$	$${\color{red}R10}$$	$${\color{red}R09}$$	$${\color{red}R08}$$	$${\color{red}R07}$$	$${\color{red}R06}$$	$${\color{red}R05}$$	$${\color{red}R04}$$
$${\color{blue}B11}$$	$${\color{blue}B10}$$	$${\color{blue}B09}$$	$${\color{blue}B08}$$	$${\color{blue}B07}$$	$${\color{blue}B06}$$	$${\color{blue}B05}$$	$${\color{blue}B04}$$
$${\color{green}G03}$$	$${\color{green}G02}$$	$${\color{green}G01}$$	$${\color{green}G00}$$	$${\color{green}G15}$$	$${\color{green}G14}$$	$${\color{green}G13}$$	$${\color{green}G11}$$
$${\color{red}R03}$$	$${\color{red}R02}$$	$${\color{red}R01}$$	$${\color{red}R00}$$	$${\color{red}R15}$$	$${\color{red}R14}$$	$${\color{red}R13}$$	$${\color{red}R11}$$
$${\color{blue}B03}$$	$${\color{blue}B02}$$	$${\color{blue}B01}$$	$${\color{blue}B00}$$	$${\color{blue}B15}$$	$${\color{blue}B14}$$	$${\color{blue}B13}$$	$${\color{blue}B11}$$
$${\color{green}G23}$$	$${\color{green}G22}$$	$${\color{green}G21}$$	$${\color{green}G20}$$	$${\color{green}G19}$$	$${\color{green}G18}$$	$${\color{green}G17}$$	$${\color{green}G16}$$
$${\color{red}R23}$$	$${\color{red}R22}$$	$${\color{red}R21}$$	$${\color{red}R20}$$	$${\color{red}R19}$$	$${\color{red}R18}$$	$${\color{red}R17}$$	$${\color{red}R16}$$
$${\color{blue}B23}$$	$${\color{blue}B22}$$	$${\color{blue}B21}$$	$${\color{blue}B20}$$	$${\color{blue}B19}$$	$${\color{blue}B18}$$	$${\color{blue}B17}$$	$${\color{blue}B16}$$

This 9 byte array being passed through the shift registers would result in LED 11 being green and all other LEDs remaining off

0b01111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111,
0b11111111

Brightness can be handled via PWM, this has not been thoroughly investigated yet but shouldn't be anything out of the ordinary

Button input handling

Button inputs are logged via the 6 input pins and some kind of circuit logic with resistors. Via the 6 input pins it's possible to derive how many buttons in a group are pressed; combining this with a scan of a row with a single red pixel it's possible to spot pressed buttons via a deviation in the voltage logic. This was figured out somewhat flukily but can be seen in action via the isButtonPressed function here.

It's significantly simpler to determine button presses if you assume only one button is pushed at a time.

Accelerometer

The accelerometer uses a 2 pin I2C interface and can be seen implemented here