New life on an old computer with Tinker Board

In 2003, I bought an HP/Compaq Presario 2100 laptop, not the best purchase that I made.  In this days of age, it is just not very useful even after I put in a solid-state hard drive and installed light-weight Linux desktop.  It just could not handle the very basic functions of web surfing.  But it seems such a waste to throw it out.

On the other hand, little single board computers, such as Raspberry Pi show  great potential.  They cost about 20 times less than what I paid for the laptop. But they do not come with a screen, keyboard/touchpad.  I recently acquired an Asus Tinker Board, which has pretty impressive performance.    With a fast microSD card, it can surf the web comfortably.   When they are networked together (but having to settle for 100Mbps Ethernet), the laptop just serves as a terminal for the Tinker Board by running VNC.  I found tigervnc to be the best. However, VNC does not pass audio.  One solution is to connect the audio output to the laptop microphone input and run loopback to the speaker (pactl load-module module-loopback latency_msec=1).  This arrangement proves to be quite usable even though the screen resolution is relatively low.  If an external monitor is attached through HDMI, synergy can be used to share the keyboard and pointer.

TI Simplelink BLE

Here we try out TI SimpleLink Bluetooth Low Energy (BLE) CC2650MODA+MSP432P401R Launchpad bundle ($35).  MSP432P401R comes with an out-of-box demo with LEDs.  We install the latest CCS 8.1.0 and SimpleLink MSP432P4 SDK (v2.20.00.12).  From the SDK, we import outofbox_msp432p401r_MSP_EXP432P401R_tirtos_ccs and  compile and upload.  After that is successful, we download SimpleLink SDK BLE Plugin (simplelink_sdk_ble_plugin_1_40_00_42) and also BLE-Stack (ble_sdk_2_02_02_25). 

We import from SimpleLink SDK BLE Plugin project_zero_MSP_EXP432P401R_tirtos_ccs.   We compile and upload.   When the USB is connected to a PC, two serial ports are created.  On Linux they are /dev/ttyACM0 and ACM1.  Connect to the serial port at 115200 baud, the following message comes up.

--------- Project Zero Example ---------

Initializing the user task, hardware, BLE stack and services.

LEDService: Registered callbacks to application.

ButtonService: registered callbacks to application

DataService: Registered callbacks to application.

LEDService: Registered service, 1 attributes

ButtonService: Registered service, 2 attributes

DataService: Registered service, 2 attributes

Scanning for Bluetooth devices, "Project Zero" should come up.   TI Android App SimpleLink SDK Explorer can be used for testing; it has a Project Zero interface to control the LED, read buttons, and send text.  On Linux, we can use hcitool lescan to scan and gatttool to test

gatttool -b A0:E6:F8:BD:EB:02 -I
[A0:E6:F8:BD:EB:02][LE]> connect
Attempting to connect to A0:E6:F8:BD:EB:02
Connection successful
[A0:E6:F8:BD:EB:02][LE]> primary
attr handle: 0x0001, end grp handle: 0x0007 uuid: 00001800-0000-1000-8000-00805f9b34fb
attr handle: 0x0008, end grp handle: 0x0008 uuid: 00001801-0000-1000-8000-00805f9b34fb
attr handle: 0x0009, end grp handle: 0x001b uuid: 0000180a-0000-1000-8000-00805f9b34fb
attr handle: 0x001c, end grp handle: 0x001e uuid: f0001110-0451-4000-b000-000000000000
attr handle: 0x001f, end grp handle: 0x0025 uuid: f0001120-0451-4000-b000-000000000000
attr handle: 0x0026, end grp handle: 0xffff uuid: f0001130-0451-4000-b000-000000000000
[A0:E6:F8:BD:EB:02][LE]> char-write-req 0x001e ff00ff
Characteristic value was written successfully
[A0:E6:F8:BD:EB:02][LE]> char-read-hnd 0x001e
Characteristic value/descriptor: ff 00 ff

When both buttons are pressed, CC2650MODA is flashed.  However, note the default project includes cc2640r2lp_simple_np_uart_pm_sble hex, which does not work with CC2650.  We replace it with simple_np_cc2650bp_uart_pm_sbl_2_02_01_18a_merge.  If there is some problem flashing, install SmartRF Flash Programmer 2 (v1.7.5).

CC2650MODA draws about 160uA when idle, and 0.1uA when in reset.  There is a 100K pull up resistor on the reset pin, which could contribute to 30uA if the reset pin is pulled low.