Cappaddy

Overview

cappaddy is a audio sample player with a capacitive touch controls; portable and battery-powered.

cap-pad-dy is a work-in-progress prototype to try out different things with capacitive touch interfaces.

Another project to learn more about ARM dev, STM32's peripherals (SPI, TIMER, DAC, DMA, TSC...) and some nice new parts like SPI flash, a new mono audio amp and a 3.3V voltage regulator/boost-converter, ideal for normal AAA cells.

Hardware (Electronics)

General Notes

Key parts:

Microcontroller: STM32F072C8

SPI Flash: Micron Serial NOR Flash Memory 128Mb - N25Q128A13EF740E-ND

Amp: TI TPA2006D1 1.45-W MONO Filter-free Class-D Audio Power Amplifier with 1.8-V

Voltage Converter: AS1337 Buck-Boost 200mA DC-DC step-up converter with buck mode

Revision 0.03

Features

• 13 touch channels (15 when UART is not used)
• Small 8 Ohm Speaker
• 16 MB SPI Flash
• Powered by 2x AAA batteries

Circuit

BOM

Reference			Value			Digikey			Count	Unit		SUM

cappaddy:U1			STM32F072x8		STM32F072C8T6-ND	1	2.00 EUR	2.00 EUR (estimated)

cappaddy:U2			N25Q128A13ESE40E	557-1562-ND		1	1.56 EUR	1.56 EUR

cappaddy:U3			TPA2006D1		296-20783-1-ND 		1	0.97 EUR	0.97 EUR

cappaddy:U4			AS1337			AS1337A-BTDTCT-ND	1	1.46 EUR	1.46 EUR
								
cappaddy:C13 C14 C17		1u			490-6423-1-ND 		3	0.09 EUR	0.27 EUR
cappaddy:C18			100pf			490-8180-1-ND 		1	0.09 EUR	0.09 EUR
cappaddy:C19			4u7			490-6407-1-ND		1	0.12 EUR	0.12 EUR
							490-12606-1-ND		0	0.13 EUR	0.00 EUR
cappaddy:C3-C6 C15 C16		100n			490-10777-1-ND		6	0.09 EUR	0.54 EUR
cappaddy:C7-C12			1n			490-6349-1-ND		6	0.09 EUR	0.54 EUR
								
cappaddy:R1-R3 R20 R27 R28	10k			CR0402-FX-1002GLFCT-ND 	6	0.09 EUR	0.54 EUR
cappaddy:R4			470R			CR0402-FX-4700GLFCT-ND 	1	0.09 EUR	0.09 EUR
cappaddy:R5-R19			1k			CR0402-FX-1001GLFCT-ND	15	0.08 EUR	1.22 EUR
cappaddy:R21-R23		100R			CR0402-FX-1000GLFCT-ND	3	0.09 EUR	0.27 EUR
cappaddy:R24			560k			1276-4267-1-ND		1	0.09 EUR	0.09 EUR
cappaddy:R25			330k			1276-4244-1-ND		1	0.09 EUR	0.09 EUR
cappaddy:R26			1M			CR0402-FX-1004GLFCT-ND	1	0.09 EUR	0.09 EUR
								
cappaddy:L1			4u7			490-6642-1-ND		1	0.39 EUR	0.39 EUR
								
cappaddy:D1			LED			511-1651-1-ND		1	0.41 EUR	0.41 EUR
cappaddy:battery_case		BC2AAAL-ND		battery_case		1	0.92 EUR	0.92 EUR

							speaker			1	1.50 EUR	1.50 EUR (estimated)

													13.16 EUR

Note: The prices of the microcontroller and the speaker were estimated, those parts were ordered on Aliexpress (Speaker: Asus Padfone 2 A68 replacement).

Digikey BOM (MCU and speaker not included):

1,557-1562-ND,cappaddy:U2
1,296-20783-1-ND ,cappaddy:U3
1,AS1337A-BTDTCT-ND,cappaddy:U4
3,490-6423-1-ND ,cappaddy:C13 C14 C17
1,490-8180-1-ND ,cappaddy:C18
1,490-6407-1-ND,cappaddy:C19
6,490-10777-1-ND,cappaddy:C3-C6 C15 C16
6,490-6349-1-ND,cappaddy:C7-C12
6,CR0402-FX-1002GLFCT-ND ,cappaddy:R1-R3 R20 R27 R28
1,CR0402-FX-4700GLFCT-ND ,cappaddy:R4
15,CR0402-FX-1001GLFCT-ND,cappaddy:R5-R19
3,CR0402-FX-1000GLFCT-ND,cappaddy:R21-R23
1,1276-4267-1-ND,cappaddy:R24
1,1276-4244-1-ND,cappaddy:R25
1,CR0402-FX-1004GLFCT-ND,cappaddy:R26
1,490-6642-1-ND,cappaddy:L1
1,511-1651-1-ND,cappaddy:D1
1,BC2AAAL-ND,cappaddy:battery_case

PCB

Get it at: OSH Park

Pinouts

/ todo

Errata / Known Bugs

• flash footprint wrong!
• R23: audio amp ~SD pin: 100R -> 100K

• audio amp: input caps -> 3.3 nF
• audio amp: decoupling cap -> 1uF
• audio amp: input resistor -> 1MOhm (- 100k) -> 200k is not bad!

• spi / flash: pullup on chip select line and pull down on clock like in datasheet? (100kOhm)

• uart connector further apart from swd connector
• uart connector wider: for pin headers, not cables
• consider pin placement inside case! - where do the physical cables connecto to what? easy assembling!!!

Hardware (Enclosure)

OnShape project

Software

Currently used/evaluated tools and sources to get the board up and running:

• Free tools for ARM development (gcc-none-eabi toolchain, OpenOCD)
• STM32CubeMX and sample code by ST
• Code::Blocks as an IDE

More notes are collected here...

Notes

TODOs

• a
• b
• c