KDE Tablet PCB

For more information, see News page. Schematics are in progress. pcb development

Many thanks to specing for coming up with the codename "Flying Squirrel" for the 7in Tablet design.

PCB Design

Features of the I/O Board include:

  • SD/MMC is wired to the STM32F (SPI mode)
  • RTC backup power from the AXP209 connected to the STM32F
  • a 0.3M-Pixel camera sensor (and source code for it which does DMA!)
  • Mic on an ADC with a PWM-based volume control
  • Stereo class D speaker outputs (1W) using MOSFET H-Bridges
  • Mini-USB PCIe WIFI socket (might see if there's room for a SIM card too)
  • Accelerometer (I2C based)
  • LVDS converter IC (this needs work)
  • SATA connector
  • Ethernet connector (need to find one)
  • USB-OTG powered (and charging, via the 2nd AXP209!)
  • 2nd USB connector

Status

  • CPU Card: all interfaces confirmed working (as of mid-september)
  • STM32F: working (and programmable). UART communication established
  • LCD Power-Enable: working (GPIO pull-up on STM32F)
  • LCD Backlight: working (GPIO pull-up 100% on STM32F instead of PWM)
  • IPS 1024x600 LCD (LVDS): working fully (power-up, display, backlight)
  • I2C Bus and devices: working (see i2cdetect below)
  • USB 4-port hub: working (see lsusb below)
  • WIFI: working with rtlwifi driver (scan at least)
  • I2C MXC6225 2-axis sensor: working (sort-of. one axis confirmed operational)
  • STM32F accessible on USB bus: confirmed (1.5K pull-up resistor needed)
  • experiment (cautiously) with AXP209 for Camera voltages: success
  • experiment (cautiously) Camera: FAIL. need to upgrade to STM32F207VCT6
  • experiment with speaker PWM output: FAIL. use DAC instead (SUCCESS)
root@debian:~# lsusb
Bus 002 Device 002: ID 0424:2514 Standard Microsystems Corp. USB 2.0 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

TODO

  • Confirm access to I2C EEPROM operational
  • forward-port touchpanel I2C experiments from 3.3-dev to sunxi-3.4 kernel
  • Confirm (again) FT5306 touchpanel working
  • experiment (cautiously) with microphone ADC input
  • compile up stm32f tools on CPU Card and add them to startup

List of I2C devices:

  • 0x51 - EOMA68 EEPROM
  • 0x34 - AXP209 (power management for the Camera, battery charger etc.)
  • 0x38 - FT5306 Capacitive Touchpanel IC
  • 0x15 - MXC6225XU 2D sensor
  • 0x21 - GC0309 camera
i2cdetect 1
WARNING! This program can confuse your I2C bus, cause data loss and worse!
I will probe file /dev/i2c-1.
I will probe address range 0x03-0x77.
Continue? [Y/n] y
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- 15 -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- 34 -- -- -- 38 -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

MXC6225

https://github.com/allwinner-ics/device_softwinner_common/blob/master/hardware/memsic/daemon/memsicd.c

Rev 2 Corrections

  • Upgrade to STM32F207VCT6 (already done on schematics)
  • VREF+ to 3.3V via 22R resistor
  • VREF- to AGND
  • 100nF capacitor between VREF+ and VREF-
  • 1.5k resistor to USBDP and 3.3V (or better, a transistor to 3.3V then 1.5k onto USBDP, with a 36k pull-down to GND and a 10k pull-up to a GPIO pin
  • BOOT1 (PB2) connect to GND
  • BOOT0 and RST resistors, change pull-ups to 10k (needs review)
  • Remove SPK_PWM_OUTR (connect to expansion instead)
  • Move MIC_ADC_IN to ADC1 (PA1) because it has DMA capability
  • Move MIC_PWM_VOL to TIM3_CH1 (PA6)
  • Move LCD_BL_EN to PE2
  • Move LCD_PWR to PE3
  • Move USB_DRV to PE4
  • Move USB0-IDDET to PE5
  • Move USB0-VBUSDET to PE6
  • Make SPK_OUT_L DAC1 (PA4)
  • Make SPK_OUT_R DAC2 (PA5)
  • CSI rewire to DCMI on STM32F207VCT6 (needs review of pin changes)
  • CSI MCLK resistor R10: 0R
  • CSI HSYNC resistor R4: 0R
  • CSI VSYNC resistor R5: 0R
  • CSI reset/stby capacitors C11 and C12 wrong: must be 104
  • CSI Q5 wrong way round (mirror-imaged, S and D reversed)
  • CSI 1V8 wrong values on capacitors and resistors
  • CSI 2V8 wrong values on capacitors and resistors
  • Remove R71 and R70 (I2C termination resistors, already on CPU Card)

DAC Audio Out

  • TDA2822D split audio in via resistor bridge 200k-2.4k, centre to 6 (or 8 for R), end to GND
  • circuit otherwise exactly as shown in application note.

Camera

lots of 100k and 390nF components, correct them based on example schematic.

ADC Audio In

gain needs to be over 100:1, 1mA on bias this means very small current! 50mV max swing needs to be scalable to 3.0v max swing, so needs to possibly be as much as 1000:1. may be better to use both LM13700s in order to avoid using MOhm resistors?

Tasks

Parts for 7in tablet

Please list parts here, then sources can be found for them as separate sections

  • 7in 1280x800 LCD
  • 7in Capacitive Touchpanel
  • Casework
  • Battery
  • PCB
  • STM32F
  • USB Connector
  • Camera
  • Accelerometer
  • PCMCIA Connector

ICs with datasheets:

Sound ICs, being evaluated:

7in LCD

TODO

Evaluate these:

7in Capacitive Touchpanel

Evaluate these:

Casework

  • Franson (of quickembed) has a rough estimate for casework development of around $USD 10,000

Battery

TODO

PCB

PCB is to be 2 or maybe 4 layers

  • Franson (of quickembed) has a rough estimate for PCB development and assembly of 1 sample of around $USD 2,000

STM32F

Decision made to use the high-end STM32F103RC, LQFP64, because of extra peripherals such as DACs and SDIO.

Resources:

USB Connector

TODO

WIFI

Camera

TODO. appx costs for 10k 0.3mp cameras: $3.00

Accelerometer

PCMCIA assembly

  • Amphenol p/n G659EU1124703T (just header)
  • Amphenol p/n G659EU1X2472X (full assembly, $1.50 10k volumes)

Parts for 10in tablet

Please list parts here, then sources can be found for them as separate sections

Commands

  • wine 'C:\Cadence\SPB_16.3\tools\pcb\bin\l2a.exe' -b 'Z:\home\lkcl\src\eoma\tablet\tablet162.max' 'Z:\home\lkcl\src\eoma\tablet\allegro'