DIO protocol
Introduction
The protocol for the DIO, 3FETs, 7FETs, RELAY and Pushbutton will be explained on this page. Most functions apply to all boards, but some don't.
This page describes both the SPI and the I2C version. See SPI versus I2C protocols for the explanation about how the protocols work in general.
Please see this page for the default adresses.
write ports
On the DIO and related boards all ports just set a single value. So writing more than one byte to such a port is redundant. The last value is the one used. The DIO boards don't have any ports that are logically a stream of bytes. So writing more than one or two bytes is not encouraged.
The DIO, 3FETS and 7FETS boards define several ports:
port | available on | function | |||
---|---|---|---|---|---|
DIO | 3/7FETs | RELAY | pushbutton | ||
0x10 | X | X | X | set all outputs (bit 0 is output 0, etc). | |
0x20 .. 0x27 | X | X | X | set one output (0x20 for output 0, 0x21 for output 1 etc) | |
0x30 | X | X | X | define pins as inputs or outputs. 0 means input, 1 means output. | |
0x40 | X | X | set current position. | ||
0x41 | X | X | set target position. | ||
0x42 | X | X | set relative position. | ||
0x43 | X | X | set stepdelay. (in tenths of a microsecond, default 200: 20ms between steps). | ||
0x50 .. 0x57 | v1.1 and up | X | Set PWM value. 0x50: output 0, 0x51 output 1 etc. | ||
0x5f | v1.1 and up | X | Set PWM mask. PWM is enabled on the outputs, who's bit is high. send 0x01 as data, to enable PWM on output 0 | ||
0x70 .. 0x77 | v1.2 and up | Select which i/o is coupled to which ADC channel | |||
0x80 | v1.2 and up | Set number of ADC channels to read | |||
0x81 | v1.2 and up | Set number of samples to add (we suggest using a power of 2) (two bytes) | |||
0x82 | v1.2 and up | Set ammounts of bits to shift accumulated sample value | |||
0xf0 | X | X | X | X | change address. |
All the above ports are read/write. I.e. if you read from that port, you will get the current value.
read ports
The DIO, 3FETS, and 7FETS boards support the following read ports:
port | available on | function | |||
---|---|---|---|---|---|
DIO | 3/7FETs | RELAY | pushbutton | ||
0x01 | X | X | X | X | identification string. (terminated with 0). |
0x02 | X | X | X | X | read eeprom (serial number). |
0x10 | X | X | read all inputs | ||
0x20 .. 0x27 | X | X | read one input (0x20 for input 0, 0x21 for input 1 etc) | ||
0x40 | X | X | read current position. | ||
0x41 | X | X | read target position. | ||
0x43 | X | X | read stepdelay. (in tenths of a microsecond, default 200: 20ms between steps). | ||
0x50 | v1.1 and up | X | Return PWM value for output 0 | ||
0x51 | v1.1 and up | X | Return PWM value for output 1 | ||
0x52 | v1.1 and up | X | Return PWM value for output 2 | ||
0x53 | v1.1 and up | X | Return PWM value for output 3 | ||
0x54 | v1.1 and up | X | Return PWM value for output 4 | ||
0x55 | v1.1 and up | X | Return PWM value for output 5 | ||
0x56 | v1.1 and up | X | Return PWM value for output 6 | ||
0x5f | v1.1 and up | X | Return PWM mask. PWM is enabled on the outputs, who's bit is high. send 0x01 as data, to enable PWM on output 0 | ||
0x60.. 0x67 | v1.2 and up | Return analog value (2 bytes) | |||
0x68 .. 0x6f | v1.2 and up | Return added and bitshifted analog value (2 bytes) | |||
0x70 .. 0x77 | v1.2 and up | Return which i/o is coupled to which ADC channel | |||
0x80 | v1.2 and up | Return number of ADC channels to read | |||
0x81 | v1.2 and up | Return number of samples to add (two bytes) | |||
0x12 | v1.2 and up | Return ammounts of bits to shift accumulated sample value |
Using the analog inputs
Setting up the ADC
Taking measurements
Will be completed ASAP (nov. 12 2012)
The built-in ADC has 10 bits of resolution, and can be used in different ways:
- Just read one single sample
- Add x samples, and optionally bitshift the result by n bits.
The first option is easy, but very prone to noise. The second option gives you the ability to filter out the noise, and/or avarage a number of samples.
To take the avarage of a number of samples, set register 0x81 to 2^n, and set register 0x82 to n. This tells the controller to sum 2^n samples, and then divide by x^n, resulting in the avarage value, which can be read from registers 0x68 .. 0x6f, depending on the channel.
For more then 10 bits of precision, it's possible to skip the bitshifting. In theory, this gives you a higher accuracy then the ADC's 10 bits. To do this, set register 0x81 to 2^n, and set register 0x82 to 0. The result can then be read from registers 0x68 .. 0x6f, depending on the channel.
examples
For SPI in the examples below, "data sent" means the data on the MOSI line, while "data received" means the data on the MISO line. when MISO reads "xx" you should ignore the data. When MOSI reads "xx" it doesn't matter what you send.
For I2C in the examples below, you should first initiate a "write" transaction with the data in the "data sent column". Don't send the "xx" bytes. Then you initiate a "read" transaction, and you will get the data in the "data received" column (and again not the "xx" bytes).
read identification
read the identification string of the board. (SPI_DIO)
data sent | data received | explanation |
---|---|---|
0x85 | xx | select destination with address 0x84 for READ. |
0x01 | xx | identify |
xx | 0x73 | 's' |
xx | 0x70 | 'p' |
xx | 0x69 | 'i' |
xx | ... | etc. |
read the identification string of the board. (I2C_DIO)
I2C master | I2C slave (i2c_dio) | explanation |
---|---|---|
START | -- | start I2C transaction |
0x84 | -- | select destination with address 0x84 for write (set port). |
0x01 | -- | identify |
STOP | -- | terminate I2C transaction. |
START | -- | start I2C transaction |
0x85 | -- | select destination with address 0x84 for READ. |
-- | 0x69 | 'i' |
-- | 0x32 | '2' |
-- | 0x63 | 'c' |
-- | ... | etc. |
Note that in the SPI example, there is bidirectional datatransfer on every cycle, but the data is "don't care" or "must ignore" (indicated by xx), while in the I2C case, the other side cannot send as there is only one data-transfer direction (indicated by "--").
turn on all outputs
data sent | data recieved | explanation |
---|---|---|
0x88 | xx | select destination with address 0x88 for WRITE |
0x10 | xx | set outputs as in bitpattern (next byte) |
0xff | xx | All outputs active. |
turn on output 4
data sent | data recieved | explanation |
---|---|---|
0x88 | xx | select destination with address 0x88 for WRITE |
0x24 | xx | port 0x24: output 4... |
0xff | xx | ... active. |
move stepper to step 0x1234
data sent | data recieved | explanation |
---|---|---|
0x88 | xx | select destination with address 0x88 for WRITE |
0x41 | xx | port 0x41: set target position |
0x34 | xx | low byte |
0x12 | xx | high byte. |