Percy has some new working eyes. His HC-SR04 ultrasonic sensors are fitted and working. Picaxe code below. Here is the B4A code:  http://jimsrobot.com/download/2013/02/PercyRobot.zip

As an overview of the results so far testing them:

• The picaxe allows you to connect the 2 middle pins of the HC-SR04 with a 1K8 resistor and send a pulse and read the pulse back from the same pin. In the pics below I’ve soldered and heat shrunk the resistors into place.
• The sensors would be great with a backing plate, I used heat glue to stick on a flexible piece of plastic.
• While the sensors work on the bench, the mission critical “don’t crash” bit isn’t so good.
• Percy has 2 sensors (leftish and rightish) , but will probably end up with 4 (leftish, forward, rightish and don’t fall off the edge)
• Couches and soft furnishings don’t reflect the sound – crash
• Chair legs seem to be too narrow to work properly – crash

Also i2c has been replaced with UART/Serial as the i2c crashed, maybe due to a race condition. The asynch serial actually uses less processing power on the Android, which is paramount for decision making as the complexity of the navigation grows. Getting the data has dropped from 10ms to 2ms.

I have a dream of building a laser range finder to go with Percy, but I’m waiting on the camera component to try to get that to work.

BTW, the code as it stands is attached above or in snippets below these pictures.

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The picaxe code with serial/uart link and averaging.

#no_table		'Speed up the programming time

HSERSETUP B115200_8, %00101

symbol PINRIGHT = c.2
symbol PINLEFT = c.1
symbol DATAIN = w0
symbol LDATA_ADD = w1
symbol RDATA_ADD = w2
symbol COUNTER = b10

main:

	let RDATA_ADD = 0
	let LDATA_ADD = 0

	for COUNTER = 0 to 5

		'Right hand sensor
		High PINRIGHT										'trigger the HC-SR04 ultrasonic
		Pulsin PINRIGHT, 1, DATAIN			'get the distance reading
		let DATAIN = DATAIN / 11

		'Clean the data
		if DATAIN > 124 then 
			let DATAIN = 124
		end if

		if DATAIN < 0 then 
			let DATAIN = 0
		end if

		let RDATA_ADD = RDATA_ADD + DATAIN 		'My Ebay sensor is calibrated to x 11

		pause 5

		'Left hand sensor	
		High PINLEFT						'trigger the HC-SR04 ultrasonic
		Pulsin PINLEFT, 1, DATAIN		'get the distance reading
		let DATAIN = DATAIN / 11

		'Clean the data
		if DATAIN > 124 then 
			let DATAIN = 124
		end if

		if DATAIN < 0 then 
			let DATAIN = 0
		end if

		let LDATA_ADD = LDATA_ADD + DATAIN 		'My Ebay sensor is calibrated to x 11

		pause 5

	next

	let RDATA_ADD = RDATA_ADD / 5
	let LDATA_ADD = LDATA_ADD / 5

	hserout 0, (b2, b4)

	debug

	goto main

Here is the connection code in the IOIO (VB4Android) – but also you need the navigation etc in the code.

Sub ReadFromUART		
	'uart order is is rx,spec,tx,spec,baud,pariy,stop

	Dim sSin As InputStream

	sSin=SER.InputStream

	If sSin.BytesAvailable > 0 Then  
		Dim bufferin(sSin.BytesAvailable) As Byte
		Dim count As Int    
		count = sSin.ReadBytes(bufferin,0, bufferin.Length)

		If count = 2 Then		
			iDistanceRight = bufferin(0) : iDistanceLeft = bufferin(1)
			lblright.Text  = iDistanceRight 
			lblLeft.Text  = iDistanceLeft 

		Else
			lblMessage.Text = "Poor Read"
			NewServiceMessage("Poor serial read" , "", 1, 500)
			'ReadFromUART
		End If
	End If
End Sub