Bluetooth communication protocol for a pressure controller
A pressure controller for a fluidic bladder has in sequence a pump, a first fluid line, a supply pressure sensor, a second fluid line, a bladder having an inlet coupled to the second fluid line, a bladder outlet coupled to a third fluid line of substantially equal length to the second fluid line, a return pressure sensor, and a fourth fluid line coupled to the return pressure sensor and returning fluid from the pump to the reservoir. A pressure estimate is formed by establishing the second fluid line length and inner diameter as the same as the third fluid line length and inner diameter, and forming the pressure estimate by averaging the supply pressure and return pressure. The pressure controller receives a setpoint pressure as a command and data over a wireless channel, and computes a head pressure offset by turning the pump off and measuring the supply and return pressures.
1. A method for a pressure controller receiving a sequence of bytes from a wireless tablet, the method comprising:
disregarding bytes received from the wireless tablet until a first byte is received with a most significant bit (MSB) of one (1), the first byte comprising bits in sequence of: 1, d7, c5, c4, c3, c2, c1, and c0, the first byte followed by a second byte with an MSB of zero (0), and comprising bits in sequence of: 0, d6, d5, d4, d3, d2, d1, and d0;
forming an unscrambled command byte from a bit sequence comprising: 0, 0, said c5, said c4, said c3, said c2, said c1, said c0;
when the unscrambled command byte identifies a read operation, performing a read operation on a device coupled to the pressure controller and specified by the unscrambled command byte;
receiving a data byte from the device specified by the unscrambled command byte;
the pressure control interface transmitting a scrambled response to the wireless tablet, the scrambled response comprising a scrambled response first byte formed by five bits of the unscrambled command byte with bit six set to an MSB value of the data byte from the device and with bit seven set to one, the scrambled response first byte followed by a scrambled response second byte, the scrambled response second byte set to the data byte from the device and with the response second byte MSB set to zero.
2. The method of claim 1 where the device is a pressure sensor.
3. The method of claim 2 where the pressure control interface and pressure sensor comprise a closed loop pressure regulation system.
4. A method for a pressure controller receiving a sequence of bytes from a wireless tablet, the method comprising:
disregarding bytes received until a first byte is received with a most significant bit (MSB) of one (1), the first byte comprising bits in sequence of 1, d7, c5, c4, c3, c2, c1 c0, the first byte followed by a second byte with an MSB of zero (0), the second byte comprising 0, d6, d5, d4, d3, d2, d1, d0;
forming an unscrambled command byte by re-arranging bits of the first byte and bits of the second byte into a sequence 0, 0, said said c5, said c4, said c3, said c2, said c1, said c0;
when the unscrambled command byte identifies a write operation, performing a write operation to a device specified by the unscrambled command byte;
receiving a data byte from the device specified by the unscrambled command byte;
transmitting a scrambled response to the pressure control interface, the scrambled response comprising a scrambled response first byte formed by five bits of the unscrambled command byte with bit six set to an MSB value of the data byte from the device and with bit seven set to one, the scrambled response first byte followed by a zero byte.
5. The method of claim 4 where the device is a pressure regulation system.
6. The method of claim 4 where the pressure control interface is part of a closed loop pressure regulation system.
7. A method for a wireless tablet transmitting a command byte and a pressure value byte to a pressure control interface, the method comprising:
forming a scrambled command byte from the command byte and the pressure value byte by setting the scrambled command byte MSB to one and the scrambled command byte bit to the MSB of the pressure value byte;
forming a scrambled data byte from the pressure value byte by setting the MSB of the scrambled data byte to zero;
transmitting the scrambled command byte and the scrambled data byte to the pressure control interface;
upon failing to receive a first byte matching the scrambled command byte followed by a second byte matching the scrambled data byte for a read command, retransmitting the scrambled command byte followed by the scrambled data byte;
upon failing to receive a first byte matching the scrambled command byte followed by a second byte of zero, retransmitting the scrambled command byte followed by the scrambled data byte.
8. The method of claim 7 where the remote device is a pressure regulation system.
9. The method of claim 7 where the wireless tablet includes a Bluetooth interface.