RE: TWI Master : SCL frequency > 400kHz

john23094 — Fri, 19 Aug 2022 14:33:12 GMT

Bumping this thread again, I too am curious at getting close to 1MHz I2C speeds. I tried the solution, setting FREQUENCY register to 0x0C380D40 (I didn't set drive strength but does this matter?) but the SCL line still clocks at exactly 400kHz.

EDIT:

Never-mind. You actually do have to set high drive strength, or it just doesn't clock at that rate.

The enum NRF_TWIM_FREQ_800K is = 209715200

nrfx_twim_config_t config =

{

.frequency = NRF_TWIM_FREQ_800K,

.scl = I2C_SCL_PIN,

.sda = I2C_SDA_PIN,

.interrupt_priority = APP_IRQ_PRIORITY_HIGH,

.hold_bus_uninit = false,

};

err = nrfx_twim_init(&_m_twi, &config, _evt_handler, NULL);

APP_ERROR_CHECK(err);

NRF_P0->PIN_CNF[I2C_SCL_PIN] &= ~GPIO_PIN_CNF_DRIVE_Msk; // Clear the drive config

NRF_P0->PIN_CNF[I2C_SCL_PIN] |= (GPIO_PIN_CNF_DRIVE_H0H1 << GPIO_PIN_CNF_DRIVE_Pos); // Set the new drive config

NRF_P0->PIN_CNF[I2C_SDA_PIN] &= ~GPIO_PIN_CNF_DRIVE_Msk; // Clear the drive config

NRF_P0->PIN_CNF[I2C_SDA_PIN] |= (GPIO_PIN_CNF_DRIVE_H0H1 << GPIO_PIN_CNF_DRIVE_Pos); // Set the new drive config

I got 815kHz which is cool. I can't comment on power consumption yet though.

RE: TWI Master : SCL frequency > 400kHz

haakonsh — Wed, 03 Jul 2019 08:42:27 GMT

The answer to all your questions is: we don't know, it's not been tested.

The FREQUENCY register is shared between TWI/TWIM/SPI/SPIM and the register value is only valid in a peripheral's own context, ie, 0x0C380D40 has a different result when used by the other serial peripherals, ie magnitude is not linear with frequency.