NexGen: Fuel Indicator: Redux v2

24 Oct 2020

I have been fighting to get my dual display board to function. The first attempt was to use a 50-pin breakout board: FAIL; The second attempt was to pin the ICs to the connector which is an IDC male with a notch (upper-left 1, lower-left, etc. FAIL; Third and final attempt worked! I said the heck with their number scheme. So I went with an old standard row 1 upper-left pin 1 - 15; lower-right pin 16 - 30 which is now over pin 1. So without further eloquence here is the 30 pin header interface listed by IC pin number:

IC Pins	Upper Display	Lower Display	Color	Header Pin	Mega256	IC Pins	Upper Display	Lower Display	Color	Header Pins	MEGA Pins
1	CLS		GREEN	9	22	32	A4	A4	ORANGE	17	I₂C.A4.25
1		CLS	PURPLE	23	50	31	A3	A3	WHITE	14	I₂C.A3.24
2	CLK		ORANGE	27	23	30	A2	A2	BLUE.	15	I₂C.A2.23
2		CLK	YELLOW	26	49	29	A1	A1	GREEN	13	I₂C.A1.22
3	WR!	WR!	BROWN	8	40	28	A0	A0	YELLOW	16	I₂C.A0.21
4	CE!		ORANGE	6	24	27	FL!		GREEN	4	27
4		CE!	BLUE	24	48	27		FL!	YELLOW	5	45
5	RST!		RED	28	25	No Pins 23 through 26
5		RST!	BLUE	3	47
6	RD!		GREEN	25	26
6		RD!	RED	7	46
No Pins 7 through 10
11	D0	D0	RED	18	I₂C.B0.1	22	D7	D7	GRAY	22	I₂C.B7.8
12	D1	D1	GRAY	12	I₂C.B1.2	21	D6	D6	WHITE	21	I₂C.B6.7
13	D2	D2	PURPLE	11	I₂C.B2.3	20	D5	D5	BLACK	20	I₂C.B5.6
14	D3	D3	BROWN	19	I₂C.B3.4	19	D4	D4	BLUE	10	I₂C.B4.5
15	na	na				18	GND	GND	BROWN
16	V_dd	V_dd	RED GRAY	1 2		17	GND	GND	BLACK
Notes: The third-time trough was the charm.

I will also use Arduino Mega pins 50, 49, 48, 47 53, 52, 51 for my two switches, using three-bit BCD code and pin 46 for the switch interrupt. I generate the interrupt by using a quad input or-gate Priority Encoder whose output EO goes to a Schmitt Trigger to actually signal for the interrupt. I got the 15 pins by 2 rows with Wire-Wrap tails from Samtec as samples.

Below are a few snaps of the test harness. Without the PanaVice with the PCB holders, this was a daunting task as you have to work on both sides at the same time. I also tried my 3M/AP Products TC-48 which never made contact with the pins, as it was made for plastic or ceramic parts that have different geometries but still fit the normal pin spacing.