filosganga
commented
10 years ago This is something I have written to emulate I2CDev, it maybe could be useful for other case. I think the q pattern can help here due to nested callback needed to deal with I2C.
function I2C(opts) {
if (!(this instanceof I2C)) {
return new I2C(opts);
}
var io;
io = opts.io;
/**
* Write multiple bits in an 8-bit device register.
* @param address I2C slave device address
* @param register Register regAddr to write to
* @param bitStart First bit position to write (0-7)
* @param length Number of bits to write (not more than 8)
* @param data Right-aligned value to write
* @param callback Callback function to call on completition.
*/
this.writeBits = function(address, register, bitStart, length, data, callback) {
// From I2CDev:
//
// bool I2Cdev::writeBits(uint8_t devAddr, uint8_t regAddr, uint8_t bitStart, uint8_t length, uint8_t data) {
// // 010 value to write
// // 76543210 bit numbers
// // xxx args: bitStart=4, length=3
// // 00011100 mask byte
// // 10101111 original value (sample)
// // 10100011 original & ~mask
// // 10101011 masked | value
// uint8_t b;
// if (readByte(devAddr, regAddr, &b) != 0) {
// uint8_t mask = ((1 << length) - 1) << (bitStart - length + 1);
// data <<= (bitStart - length + 1); // shift data into correct position
// data &= mask; // zero all non-important bits in data
// b &= ~(mask); // zero all important bits in existing byte
// b |= data; // combine data with existing byte
// return writeByte(devAddr, regAddr, b);
// } else {
// return false;
// }
// }
var mask;
io.sendI2CWriteRequest(address, register);
io.sendI2CReadRequest(address, 1, function(value) {
var mask;
if(value != 0) {
mask = ((1 << length) - 1) << (bitStart - length + 1);
data = data << (bitStart - length + 1);
data = data & mask;
value = value & ~(mask);
value = value | data;
io.sendI2CWriteRequest(address, register);
io.sendI2CWriteRequest(address, value);
callback(true);
}
else {
callback(false);
}
});
};
/**
* Write a single bit in an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr Register regAddr to write to
* @param bitNum Bit position to write (0-7)
* @param value New bit value to write
* @return Status of operation (true = success)
*/
this.writeBit = function(address, register, bit, data, callback) {
/*
* From I2CDev
* bool I2Cdev::writeBit(uint8_t devAddr, uint8_t regAddr, uint8_t bitNum, uint8_t data) {
* uint8_t b;
* readByte(devAddr, regAddr, &b);
* b = (data != 0) ? (b | (1 << bitNum)) : (b & ~(1 << bitNum));
* return writeByte(devAddr, regAddr, b);
* }
*/
io.sendI2CWriteRequest(address, register);
io.sendI2CReadRequest(address, 1, function(value) {
if(data != 0) {
value = value | (1 << bit)
} else {
value = value & ~(1 << bit)
}
io.sendI2CWriteRequest(address, register);
io.sendI2CWriteRequest(address, value);
callback();
}
};
/** Read multiple bytes from an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr First register regAddr to read from
* @param length Number of bytes to read
* @param data Buffer to store read data in
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Number of bytes read (-1 indicates failure)
*/
this.readBytes = function(address, register, length, data, callback) {
io.sendI2CWriteRequest(address, register);
io.sendI2CReadRequest(address, callback);
};
/** Read multiple bytes from an 8-bit device register.
* @param devAddr I2C slave device address
* @param regAddr First register regAddr to read from
* @param length Number of bytes to read
* @param data Buffer to store read data in
* @param timeout Optional read timeout in milliseconds (0 to disable, leave off to use default class value in I2Cdev::readTimeout)
* @return Number of bytes read (-1 indicates failure)
*/
this.readByte = function(address, register, data, callback) {
readByte(address, register, 1, data, callback);
};
}
soundanalogous
rwaldron
dtex
Starting from conversation here: https://github.com/rwaldron/johnny-five/pull/293#issuecomment-32135307
This is discuss implementing a generic class for I2C IMUs, eg. https://www.sparkfun.com/categories/160
cc @filosganga @soundanalogous @divanvisagie @reconbot