I have talked about the Fuel load Indicator twice before, first here and then here. So here is the hardware design and its analysis.

Analysis:  In my last blog I noted that between the display and the switches I am using about 25 pins + ground and power. So to recap here are the pins: I have added a second table which shows the I/O connections. The reason that I chose the STM32 was for its size. It can easily fit inside the enclosure (approximately 7cm square).

The Plan:

The Hardware: Since the original back will be of no use to me I will have to print a new one. I will have two connectors on the rear. 1) a DB-7 for my CANbus Data and  2) a DIN 5 for my 5 volts. I will have to use UTA, the University of Texas at Arlington, Maker Space Laser Cutter to cut my vector board (FR4 PCB) to shape. In this way,  I can put my connect the STM32xx and the two  (2) TI PCF8574 I/O expanders.

The Software Overview: The software design is rather simple as the STM32 is just being used as a dumb terminal but without the keyboard This will only need 4 keys And instead of a UART and  RS-232RS-232 I will be using a CANbus transceiver

Display Info
MnemonicJ1 pinsIO ExpSTM32
D61IC1-11
D42IC1-9
GND display3
GND logic4
D05IC1-4
D56IC1-10
D37IC1-7
D18IC1-5
A19IC2-5
D210IC1-6
A011IC2-4
A212IC2-6
FL - Not Used13
CLS.11410
CLS.21511
WR16

 

12
CE.21713
RD.2 - Not Used18
RD.1 - Not Used19
CE.12014
D7.222
CLK.22115
CLK.12316
D7.124IC1-12
RST.12517
RST.22629
A3 & A427IC2-9
Vcc28
A3 & A429IC2-7
Vcc30

 

I/O Interfaces
MnemonicSTM32Header
USB-
USB+
CanRX45
CanTX46
SDA222
SCL221
Switches
Test-C3
FILL394
TEST405
Set-C3
Set-UP411
Set-DOWN422
Keep Tuned In, More To Come   ~~Cris 
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