1. Introduction
This document describes how to collect data from your Mitch device using the Bluetooth Low Energy (BLE) functionalities provided by MATLAB®.
This example is based on the standard Mitch communication protocol [A] and MATLAB® official documentation, as described in our Muse quick start guide [B]:
2. Collect Data from your Mitch
This example shows how to collect and plot pressure sensors data from your FSR-enabled (i.e., Force Sensitive Resistor membrane) Mitch device using the BLE communication support provided by MATLAB® functions.
First, check that the BLE device is powered on and support connections by finding it in MATLAB® using the blelist function. After the device has been found in MATLAB®, connect to it by calling the ble function. Specify the name of the device if the name is unique or specify the device address.
%% Discover and connect to Muse device
devlist = blelist;
muse = ble("mitch_0101");
Access the Mitch Custom Service and relative command and data characteristics, to get the corresponding UUIDs.
%% Access custom service and characteristics of interest cmd = characteristic(muse, "C8C0A708-E361-4B5E-A365-98FA6B0A836F", ... "D5913036-2D8A-41EE-85B9-4E361AA5C8A7"); dat = characteristic(muse, "C8C0A708-E361-4B5E-A365-98FA6B0A836F", ... "09BF2C52-D1D9-C0B7-4145-475964544307");
Next, enable subscription to both command and data characteristics.
%% Subscribe to characteristic notify subscribe(cmd); subscribe(dat);
Check device status, before starting acquisition. In a very similar way it is also possible to retrieve the device configuration.
%% Get device status (i.e., just to check setup consistency) % GET_STATE command code (hex): 0x82 write(cmd, [130 0]); cmd_response = read(cmd); state = displayDeviceState(cmd_response);
Then, we can activate the acquisition as follows.
%% Start data acquisition in STREAMING mode
% To stop acquisition at runtime, write the following command on Command
% Window: write(cmd, [2 1 2]). It set the device in SYS_IDLE state.
if (state == 2)
% SET_STATE command code (hex): 0x02
% streaming type: 0xF8 (continuous streaming)
% acquisition mode: 0x01 (pressure only)
% acquisition freq: 0x01 (5 Hz)
write(cmd, [2 3 248 1 1]);
else
disp('Acquisition already running.');
end
The data acquisition is managed through a dedicated callback function assigned to the DataAvailableFcn property of the data characteristic.
%% Visualize data as Pressure Map
% set the color map to be used
prsColors = parula(256);
side = 1; % Choose foot side: 0 = right, 1 = left
if (side==0)
% right foot
s_pos = [0,0;0,-2;1,-2;2,-2;3,-2.5;0,-3;1,-3;2,-3;3,-3.5;3,-4.5;3,-5.5;...
3,-7.5;2,-8.5;3,-8.5;1.5,-9.5;2.5,-9.5];
else
% left foot
s_pos = [0,0;-3,-2.5;-2,-2;-1,-2;0,-2;-3,-3.5;-2,-3;-1,-3;0,-3;-3,-4.5;...
-3,-5.5;-3,-7.5;-3,-8.5;-2,-8.5;-2.5,-9.5;-1.5,-9.5];
end
% Set initial position of pads in the map
figure; hold all;
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0.2, 0.1, 0.6, 0.85]);
for i = 1:16
pads{i} = plot(s_pos(i,1),s_pos(i,2),'sk','MarkerSize',35);
end
ylim([min(s_pos(:,2))-1 max(s_pos(:,2))+1])
axis equal, xticks(''), yticks(''), g=gca; g.XAxis.Visible = 'off';
g.YAxis.Visible = 'off'; g.Color = [.94 .94 .94];
% Assign data callback
dat.DataAvailableFcn = @displayCharacteristicDataPressureMap;
The result plot will be a pressure map of the foot.
