Got this working with a few code changes:
/*
* read_wiper - returns the 2nd byte of a 2-byte read from the specified
wiper
* 'reg' contains the write command to read the required wiper
*/
uint8_t read_wiper(uint8_t reg)
{
uint8_t dataByte;
//initialise i2c2 device
init_i2c();
//set I2C2_CNT register to 1 for initial write command
I2C2_CNT = 1;
while (I2C2_STATUSRAW & 0x1000);
//poll 'busy bit' in I2C2_STATUSRAW register (bit 12) until it is
zero
//set transmit mode
I2C2_CON = 0x8601;
//load data register with write command
I2C2_DATA = reg;
while (!(I2C2_STATUSRAW & 0x0010));
//poll XRDY bit in I2C2_STATUSRAW register (bit 4) until it is
non-zero
//data has transmitted, write 1 to clear the interrupt
I2C2_STATUSRAW |= 0x0010;
while (!(I2C2_STATUSRAW & 0x0004));
//poll 'access ready' bit in I2C2_STATUSRAW register (bit 4) until
it is non-zero
//set byte count to 2
I2C2_CNT = 2;
//set receive mode
I2C2_CON = 0x8400;
//set start and auto stop condition
I2C2_CON |= 0x0003;
while (!(I2C2_STATUSRAW & 0x0008));
//poll 'receive ready bit' in I2C2_STATUSRAW register (bit 3) until
it is non-zero
dataByte = I2C2_DATA; //first byte is always 0x00
//data has been received, write 1 to clear the interrupt
I2C2_STATUSRAW |= 0x0008;
while (!(I2C2_STATUSRAW & 0x0008));
//poll 'receive ready bit' in I2C2_STATUSRAW register (bit 3) until
it is non-zero
dataByte = I2C2_DATA; //second byte is the value we want
//data has been received, write 1 to clear the interrupt
I2C2_STATUSRAW |= 0x0008;
while (!(I2C2_STATUSRAW & 0x0100));
//poll 'buss free' bit in I2C2_STATUSRAW register (bit 8) until it
is non-zero
//clear all pending interrupts
I2C2_STATUS = 0x7FF;
return dataByte;
}
Note the clearing of pending interrupts after each check and the final
clear of the status register (not status_raw) at the end. 5 byte writes now
working every time...
On Thursday, 13 September 2018 14:39:04 UTC+1, lazarman wrote:
>
> I love the TRM documentation its very detailed best to follow its
> recommended sequences and roll your own code using examples as a template.
>
> I'd look at the i2C slave data sheet carefully especially the timing/setup
> diagrams.
> you have the scope looks like your close.Another idea look for example
> code for device even if another micro. Looking at it might give you a clue
> what's wrong. Last attempt try something quick and simple if you have
> available no OS barebones one processor I bet your code works on it.
> Good Luck
>
>
> Sent from Yahoo Mail on Android
> <https://overview.mail.yahoo.com/mobile/?.src=Android>
>
> On Thu, Sep 13, 2018 at 8:06 AM, Hugh Frater
> <[email protected] <javascript:>> wrote:
> Does anyone know the correct programming sequence for doing an I2C random
> read from within the PRU? I've tried this nicely written driver:
>
> https://github.com/LinuxDroneLab/pru-i2c-lib
>
> It works less than my code does...
>
> My code works fine if I call my routine once, on the scope I see the write
> followed by the read of the 2 bytes I want... Call my function again and
> all I see is the read.
>
> Code and scope grabs attached - the documentation on the I2C module from
> within the AM335xTRM pdf is shocking and this problem is driving me mad...
>
> /*
> * read_wiper - returns the 2nd byte of a 2-byte read from the specified
> wiper
> * 'reg' contains the write command to read the required wiper
> */
> uint8_t read_wiper(uint8_t reg)
> {
>
> uint8_t dataByte;
>
> //initialise i2c2 device
> init_i2c();
>
> //set I2C2_CNT register to 1 for initial write command
> I2C2_CNT = 1;
>
> while (!(I2C2_STATUSRAW & 0x0100));
> //poll 'buss free' bit in I2C2_STATUSRAW register (bit 8) until it
> is non-zero
> //set transmit mode
> I2C2_CON = 0x8601;
> //load data register with write command
> I2C2_DATA = reg;
>
> while (!(I2C2_STATUSRAW & 0x0004));
> //poll 'access ready' bit in I2C2_STATUSRAW register (bit 4) until
> it is non-zero
> //set byte count to 2
> I2C2_CNT = 2;
> //set receive mode
> I2C2_CON = 0x8403;
>
> while (!(I2C2_STATUSRAW & 0x0008));
> //poll 'receive ready bit' in I2C2_STATUSRAW register (bit 3)
> until it is non-zero
>
> dataByte = I2C2_DATA; //first byte is always 0x00
>
> //zero the receive ready bit once we have read the 1st byte into our
> local variable
> I2C2_STATUSRAW |= 0x0008;
>
> while (!(I2C2_STATUSRAW & 0x0008));
> //poll 'receive ready bit' in I2C2_STATUSRAW register (bit 3)
> until it is non-zero
>
> dataByte = I2C2_DATA; //second byte is the value we want
>
> //zero the receive ready bit once we have read the 2nd byte into our
> local variable
> I2C2_STATUSRAW |= 0x0008;
>
> while (!(I2C2_STATUSRAW & 0x0100));
> //poll 'buss free' bit in I2C2_STATUSRAW register (bit 8) until it
> is non-zero
>
> return dataByte;
> }
>
> void init_i2c()
> {
> /* Enable I2C2 clock signal generation */
> while (!(CM_PER_I2C2 & 0x2))
> CM_PER_I2C2 |= 0x2;
>
> /*
> * set I2C2_PSC register to 0x0B
> * set I2C2_SCCL register to 0x0D
> * set I2C2_SCCH register to 0x0F
> * set I2C2_CON register to 1000 0110 0000 0000 (0x8600)
> * set I2C2_SA register to 0x2E (address of MCP4641)
> */
>
> I2C2_PSC = 0x000B;
> I2C2_SCLL = 0x000D;
> I2C2_SCLH = 0x000F;
> I2C2_CON = 0x8600;
> I2C2_SA = i2cPotAddress;
> I2C2_BUF = 0x0000;
>
> }
>
> [image: 20180913135820.png]
>
> [image: 20180913135835.png]
>
>
>
>
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